In this post, I’ll show you how to prune tomatoes, peppers, and eggplants after winter to remove frost damage, encourage healthy new growth, and set your plants up for an early and productive harvest. I’ll also help you decide when it’s time to remove a struggling plant—sometimes a fresh start is the best option for a healthy and productive garden. Let’s get your overwintered plants ready for spring.

In This Post:

• When to Prune Tomatoes, Peppers, and Eggplants After Winter
• How to Prune Tomatoes, Peppers, and Eggplants After Winter
• Fertilize for Recovery
• Water Deeply and Consistently
• When to Replace a Plant
• The Benefits of Pruning Overwintered Plants
• Common Questions About Overwintered Plants
• Additional Tips for Overwintered Crops
• A Quick Checklist for Overwintered Plants

Step 1: When to Prune Tomatoes, Peppers, and Eggplants After Winter

Timing is everything when it comes to pruning overwintered tomatoes, peppers, eggplants and basil. Before you start, wait until the danger of frost has passed, temperatures are beginning to warm, and you see signs of spring. Plants will typically put on new growth as the weather shifts, making it easier to see what’s worth keeping and what needs to be removed. To know when it’s safe to begin, look up your local last frost date here. Being patient at this stage ensures your plants have the best chance to recover and thrive.

It’s tempting to remove frost-damaged sections right away, but patience is key. Those damaged areas are actually protecting the plant. If you prune too early and it freezes again, the plant may not recover. 

How to Evaluate:

• Look for sturdy stems and signs of new growth. If you see healthy, green sections, the plant is likely worth keeping.
• If the plant is mostly damaged, diseased, or struggling, consider replacing it with a new transplant in a different location to give yourself a fresh start for the season.

If you’re looking for a complete guide to growing pepper plants from the ground up, be sure to check out my post on how to grow peppers. Chiltepin, a tiny but mighty desert pepper, often survives mild winters and regrows from the base. Learn more in how to grow chiltepin.

Step 2: How to Prune Tomatoes, Peppers, and Eggplants After Winter

Once you decide to keep a plant, proper pruning is the next step to encourage new growth and a productive season. Pruning helps remove damaged areas, shapes the plant for better airflow, and directs its energy toward healthy new shoots.

1. Remove Damaged and Dead Growth

• Start by inspecting the plant for frost-damaged, dead, or diseased branches. These won’t recover and can invite pests or disease.
• Use clean, sharp pruning shears to make precise cuts.
• Sanitize your tools between plants using a diluted bleach solution or rubbing alcohol to prevent the spread of disease.

2. Prune Above New Growth

• Look for healthy leaves or buds beginning to emerge.
• Cut just above the point where new growth is forming. This signals the plant to redirect energy into producing strong new shoots.
• Avoid cutting too far back into healthy growth—doing so can stunt the plant’s recovery.

3. Shape the Plant for Better Growth

• Tomatoes: Remove weak, spindly stems and suckers (small shoots that grow between the main stem and a branch). This helps improve airflow and allows the plant to focus on producing fruit.
• Peppers & Eggplants: These plants don’t need heavy pruning, but you can thin out excess growth in the center of the plant to improve airflow and reduce disease risk.

4. Remove Low-Hanging or Crowded Stems

• Trim stems touching the ground or growing too densely in the middle of the plant.
• This improves air circulation, reducing the chance of fungal diseases like powdery mildew or blight.

5. Allow Time for Recovery

• Pruning encourages growth, but it also stresses the plant. Give it a few days to adjust before fertilizing or watering heavily.
• If the plant seems slow to recover, ensure it’s getting enough warmth and nutrients from the soil.

6. Monitor for Additional Pruning Needs

• Over the next couple of weeks, keep an eye on how the plant responds.
• If new growth appears strong, you’re on the right track. If weak, leggy growth appears, you may need to pinch off extra stems to encourage bushier growth.

Quick Tips for Pruning Success

✔ Wait until after the last frost before pruning to avoid exposing tender new growth to cold damage.
✔ Always prune on a dry day to reduce the risk of fungal infections.
✔ Remove no more than ⅓ of the plant at a time to prevent excessive stress.
✔ Mulch around the base after pruning to protect roots and retain moisture.

Step 3: Fertilize for Recovery

Overwintered plants have worked hard to survive the winter, depleting nutrients along the way. Once you’ve pruned your plants, you’re signaling them to start growing again, and they’ll need the right support to thrive. Here’s how to give them what they need:

• Feed the Soil First: Start by adding worm castings and compost to the soil around the plant. These organic amendments provide a steady, natural source of nutrients and help improve soil structure. Healthy soil is the foundation for healthy plants.
• Use Light Doses of Fertilizer: After pruning, apply a small amount of a balanced organic fertilizer or one designed for fruiting vegetables. Light doses are more effective than large amounts, especially if the plant has lost many of its leaves, as the plant may need time to rebuild its canopy before taking up more nutrients.
• Feed When Plants are Actively Growing: Plants need to be actively growing to utilize fertilizer effectively. As the soil warms, plants will better absorb and use the nutrients you’ve provided.

Step 4: Water Deeply and Consistently

Proper watering is critical for overwintered plants, but it’s important to remember that these plants have already developed deep root systems, which can work to your advantage. Here’s how to keep them hydrated without overwatering:

• Water Based on Soil Needs: Until temperatures climb, overwintered plants may need less frequent watering than you’d expect. Always check the soil first—allow the top 2–3 inches to dry out before watering again.
• Water Deeply: When you do water, aim for deep soaking to penetrate the root zone. This helps encourage the roots to grow stronger and reach deeper into the soil for moisture.
• Adjust Watering as Temperatures Rise: As the weather warms, water more often, but keep soaking deeply to encourage strong roots.
• Refresh Mulch: Add a thick layer of mulch around plants to hold moisture, keep the soil cool, and protect the roots. If your mulch has thinned over winter, now’s a good time to top it off.

Step 5: Replace If Needed

If your plant shows no new growth a couple of weeks after your last frost date, it’s likely time to let it go. Removing a struggling plant and starting fresh with a new transplant can be the better option for a healthy, productive garden. Plant in a new location to prevent pest and disease build up in the soil. 

The Benefits of Pruning Overwintered Plants

Successfully pruning overwintered tomatoes, peppers, and eggplants can reward you with an earlier harvest. Once nighttime temperatures stay above 55°F, they’ll begin setting fruit weeks ahead of new transplants. This head start can make a big difference in the low desert, where spring’s growing season is short.

For tomato care after summer instead of winter, this post explains how to prune and revive over-summered tomato plants in Arizona.

Common Questions About Pruning Tomatoes, Peppers, and Eggplants After Winter

Q: My overwintered plant looks lifeless. Should I pull it?

A: Not necessarily. Check the stems—if they’re still green or new shoots are forming, give it time. Plants in the low desert often bounce back as temperatures warm. Be patient and monitor for signs of new growth before deciding whether to prune or remove the plant entirely.

Q: Should I fertilize immediately after pruning?

A: Yes, but stick to a light dose after pruning tomatoes, peppers, or eggplants. This provides nutrients to support recovery without overwhelming the plant, especially if it has lost a lot of leaves. Light feeding is ideal for helping plants rebuild their canopy.

Q: How can I protect my overwintered plants from late frosts?

A: Keep frost cloth or other coverings on hand and use them whenever temperatures are forecasted to drop below 32°F. Cover plants overnight and remove the coverings in the morning once the temperature rises. This step is critical after pruning tomatoes, peppers, or eggplants since exposed new growth is more vulnerable to frost damage. Learn more about how to protect your garden from frost in this guide.

Q: Should I pull out an overwintered plant and move it to a new spot?

A: No. Removing the plant will likely kill it because established roots don’t handle transplanting well. Instead, focus on pruning tomatoes, peppers, or eggplants properly and amend the soil around them with compost and worm castings to replenish nutrients. Plan to rotate crops when planting new transplants in the future.

Q: Will my squash, cantaloupe, or watermelon plants come back next season?

A: No, these plants are annuals and won’t survive through winter. Unlike tomatoes, peppers, and eggplants (which are perennials under favorable conditions), these crops complete their lifecycle in one season.

Q: What’s the best way to remove a plant if I decide it’s time?

A: Cut the plant off at the base, leaving the roots intact in the soil. As the roots decompose, they’ll add organic matter and improve soil structure. However, if the plant is diseased, remove all plant material from the garden to prevent spreading pathogens.

Q: Should I practice crop rotation with overwintered plants?

A: While crop rotation is important for new plantings, overwintered plants don’t need to be moved. After pruning tomatoes, peppers, or eggplants, replenish the soil with compost and worm castings. When you replace the plant entirely, plan to rotate crops to a different spot.

Q: How do I know if an overwintered plant is worth saving?

A: Look for signs of life, such as green stems or new shoots. If the plant is mostly damaged, diseased, or not putting out new growth after a couple of weeks of warmer weather, it’s better to remove it and replace it with a fresh transplant.

Q: Can I overwinter other vegetables like lettuce or carrots?

A: Most cool-season vegetables like lettuce, carrots, and spinach are annuals and won’t overwinter. However, some herbs like rosemary, oregano and perennials like asparagus can thrive year after year if conditions are right. Learn more about perennials in this guide.

Q: How often should I water overwintered plants?

A: Water deeply but infrequently. Always check the soil first and let the top 2–3 inches dry out before watering. As temperatures rise, you may need to water more often, but focus on deep watering to support the plant’s established root system.

Q: Why aren’t my overwintered plants setting fruit yet?

A: Fruit production typically begins when nighttime temperatures stay consistently above 55°F. Until then, focus on pruning tomatoes, peppers, and eggplants properly, fertilizing lightly, and supporting healthy growth.

Additional Tips for Overwintered Crops

• Companion Planting: Add basil, marigolds, or alyssum near your recovering plants to attract beneficial insects and improve pollination. These companion plants are especially helpful after pruning tomatoes and other crops. Learn more about companion planting in this guide.
• Pest Monitoring: Overwintered plants can harbor pests like aphids or spider mites. Remove plants and replant rather than treat them if plants are heavily infested.
• Mulching: Add mulch around the base of your plants to regulate soil temperature, retain moisture, and protect the root zone. Refresh mulch as needed after pruning. Learn what to use for mulch in this guide.

Quick Checklist for Pruning Tomatoes, Peppers, and Eggplants After Winter

• Evaluate the Plant: Keep it if there’s new growth; remove it if it’s severely damaged.
• Prune Carefully: Remove damaged areas after the last frost, cutting above healthy growth.
• Fertilize Lightly: Feed the plant after pruning and continue as needed throughout the growing season.
• Water Consistently: Water deeply and let the top 2–3 inches of soil dry out before watering again.
• Replace if Needed: Remove plants that show no signs of life and start fresh with a new transplant.

Related Posts

• How to Start Seeds Indoors
• Pruning Peppers in Hot Summer Climates
• How to Grow Tomatoes in Arizona: 10 Tips for Success
• How to Plant Tomatoes: A Step-by-Step Guide
• Prevent Blossom End Rot: Tips for Healthy Tomatoes
• Turning Green Tomatoes Red: 4 Ways to Ripen Green Tomatoes

Caring for overwintered crops takes some patience, but the rewards—earlier harvests and less replanting—make it worthwhile. Have you tried pruning overwintering warm-season crops? Share your experience in the comments below—I’d love to hear what’s worked for you! And don’t forget to pin this post for future reference.

The post How to Prune Tomatoes, Peppers, and Eggplants After Winter appeared first on Growing In The Garden.

Understanding Frost Sensitivity in Citrus Trees

Not all citrus trees are created equal when it comes to cold tolerance. Some varieties can withstand lower temperatures, while others are highly sensitive and require extra care.

Most Cold-Hardy Citrus Trees:

Kumquat and Mandarin trees are the champions of cold tolerance among citrus, enduring temperatures as low as 18°F to 20°F (-7.7°C to -6.6°C).

Moderately Cold-Hardy Citrus Trees:

Grapefruit and Orange trees can tolerate temperatures down to the mid-20s°F (-3.8°C).

Least Cold-Hardy Citrus Trees:

Lemon and lime trees, especially, are highly frost-sensitive, often suffering damage at 32°F (0°C). They typically do not go into dormancy, making them more vulnerable to frost. Learn which other plants are sensitive to frost in this guide.

5 Tips for Protecting Your Citrus Trees During Freezing Temperatures

1. Monitor Temperatures Closely

Critical Threshold: Fruit damage may occur after several hours below 27°F (-2.7°C).
Action: If a significant drop is forecasted, take preventive measures like watering the soil (moist soil retains heat better) and covering the trees.

2. Cover Citrus in Containers and Young or Newly-Planted Trees

Why: Citrus in containers and newly planted or young citrus trees are more susceptible to frost damage.
How: Use frost cloth, drop cloths, or burlap to cover the entire tree, extending all the way to the ground to trap heat from the soil. Learn more about how to protect plants from frost in this guide.
Duration: Keep them covered during freezing nights for 3-5 years after planting. Once plants are larger and more established, they can better withstand freezing temperatures.

3. Use Proper Plant Placement

Warmest Spots: Plant citrus trees in the warmest areas of your yard, such as south-facing spots that receive maximum sunlight.
Avoid Cold Pockets: Stay away from low-lying areas where cold air settles.
Windbreaks: Utilize fences or hedges to protect trees from cold winds.

4. Take Container Grown Citrus Indoors in Cold Winter Areas

Why: If you live in an area that experiences freezes often, growing citrus in containers allows you to move them indoors or to a sheltered location like a greenhouse during the winter.
Tips: Use large pots with good drainage and choose dwarf varieties suited for container growth.

5. Wait to Prune

Timing: Avoid fall pruning and wait until after the danger of frost has passed in the spring to prune any frost-damaged limbs and branches.
Why: Pruning in the fall stimulates new growth that is vulnerable to frosts. Frost-damaged sections are protecting the rest of the tree from further damage. Removing them exposes new areas to damage if there are additional freezing temperatures. Learn more about how and when to prune fruit trees in this guide.

Keeping your citrus trees alive during the coldest months requires a bit of vigilance and care, but the rewards are well worth the effort. Frost is temporary, but the joy of harvesting your citrus can last for years. Stay attentive to weather forecasts, have your protective materials ready, and your citrus trees will thank you with bountiful harvests season after season.

More Citrus Growing Resources:

• Which Type of Citrus to Plant
• 10 Tips for Growing Citrus in Containers
• How to Grow Citrus in Arizona
• 10 Biggest Citrus Growing Mistakes
• Tips for Juicing Citrus
• Choosing Citrus Varieties for Hot-Zone Climates – (Guest post for Gardener’s Supply Company)
• How to Fertilize Citrus Trees

If this post about protecting citrus from freezing temperatures was helpful, please share it.

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Article Outline:

Understand Frost and its Risks

1. Learn when to expect freezing temperatures
2. Choose the best location in your yard for frost-tender plants
3. Learn which plants need protection during frost events
4. Prepare before it freezes
5. How to protect plants during a freeze
6. What to do after a frost

Understand Frost and its Risks

Frost occurs when temperatures drop below freezing, causing ice crystals to form on plant surfaces. Frost on the plant disrupts the movement of fluids within the plant and dries it out, leaving behind brown and crispy damage.

• Light freeze: 29°F to 32°F (-1.6°C to 0°C). Tender plants are often killed.
• Moderate freeze: 25°F to 28°F (-3.88°C to -2.22°C). Causes damage to many plants.
• Severe freeze: 24°F (-4.44°C) and colder. Causes heavy damage to many plants.

Use a minimum/maximum thermometer to measure your local temperature accurately. The weather app reading on your phone may not be accurate for your yard.

In hot climates, frost can be particularly damaging because many plants are adapted to warmer conditions and may not be able to tolerate sudden cold snaps. Even a light frost can damage leaves, flowers, and fruit, leading to reduced yields or even plant death.

If you would like to learn more about the principles of successful desert gardening, my guide, “Desert Gardening: How to Grow Vegetables in a Hot, Dry Climate,” may be helpful.

Some factors that make plants more or less susceptible to damage from freezing temperatures include:

• Dormancy — A dormant plant will have less damage than a tree or plant that is actively growing. This is why a sudden frost early in the season will often do more damage than a frost later in the season after plants have adjusted to colder temperatures.
• Watering — Well-watered plants withstand freezing temperatures better than dehydrated plants. The water in the soil also helps to insulate the soil.
• Pruning — Newly pruned areas of the plant are more susceptible to frost damage.
• Newly planted — Less-established root systems of new plants are more likely to be damaged by frost. Plant cold-sensitive crops after the last frost date in your area, and consider using frost-tolerant varieties for winter gardening.
• Plants in containers — Container-grown plants are subject to higher fluctuations in temperature than in-ground plants. They are more likely to suffer damage in a freeze.
• Lower temperatures, more prolonged exposure to freezing temperatures, and rapid drops in temperature cause more damage.

6 Tips for Protecting Your Garden from Frost in Mild Winter Climates

1. Learn when to expect freezing temperatures

An essential tool in knowing when freezing temperatures are most likely is knowing your average first and last frost dates. You can look them up here using your zip code if you live in the United States.

Frost is most likely on clear, calm nights with few clouds and low humidity. Cold winds also decrease the temperature. During the day, the sun warms the soil, and that heat is released throughout the night. So, the coldest temperatures of the night occur just before dawn.

2. Choose the best location in your yard for frost-tender plants

Take advantage of natural microclimates in your garden.

Plant frost-tender trees and plants in the warmest areas of your yard. An area with a western or southern exposure with reflected heat from a block wall will be warmer than other areas in your landscape. The heat absorbed by a block wall throughout the day will radiate during the night.

Cold air moves downslope and settles in the lowest spots. The cold spots in your yard are good for planting fruit trees that need chill hours and other cold-loving plants.

3. Learn which plants need protection during frost events

Most cool-season vegetables, herbs, and flowers do not need to be covered. However, if you are trying to overwinter warm-season crops like tomatoes, eggplants, and peppers, they should be covered during frost events. Tropical plants and landscape plants like lantana and hibiscus are also frost-sensitive. This guide explains which vegetables, flowers, and landscape plants to cover when it freezes.

Citrus trees, especially young or newly planted citrus, are also susceptible to frost damage. Certain types of citrus are more frost-sensitive than others. Learn more about protecting citrus from freezing temperatures in this guide.

4. Prepare before it freezes

Harvest mature fruits or vegetables before a hard frost to avoid losing crops. If prolonged freezing temperatures are expected, harvest tomatoes and allow them to ripen indoors. Learn more about how to turn green tomatoes red in this guide.

Water plants well before a frost event. Watering your garden before a frost can help protect plants. Moist soil retains heat better than dry soil, so giving your plants a good soak before a cold night can help keep the ground warmer. However, avoid overwatering, as wet soil can lead to root rot in colder conditions.

Mulching is one of the simplest and most effective ways to insulate your garden against frost. A thick layer of organic mulch, such as straw, leaves, or compost, helps retain soil warmth and protect plant roots from freezing.

Have frost cloth, row covers, burlap, or old sheets on hand before it freezes. Frost cloth is a lightweight, breathable fabric that can be draped over plants to provide a few degrees of protection from frost. Row covers can also protect larger areas or multiple plants at once.

Use cold frames and cloches to protect plants. Cold frames and cloches are excellent tools for protecting individual plants or small sections of your garden. A cold frame is a mini-greenhouse that traps heat and shields plants from frost, while cloches are small covers placed over individual plants. Both can provide significant protection from frost and extend your growing season.

5. How to protect plants during a freeze

• Use frost cloth, burlap, drop cloths, sheets, blankets, or even newspapers to cover plants. Do not use plastic. Frost cloth is a lightweight, breathable fabric that can be draped over plants to provide a few degrees of protection from frost. It’s important to secure the cloth so it doesn’t blow away and to ensure it doesn’t touch the plant’s foliage directly. Row covers can also be used to protect larger areas or multiple plants at once.
• Cover plants before sundown to trap the stored heat from during the day. The heat may have dissipated if you wait to cover it until after nightfall.
• Cover the plant completely, allowing the cover to drape down to the soil around the plant. This traps the warmth inside. Don’t gather the cover around the trunk; it won’t trap radiated heat from around the plant.
• Wrap trunks of frost-sensitive trees and young trees loosely with multiple layers of cloth. This can be left in place all winter.
• Use styrofoam cups to protect the growing tips of cactus.
• Add heat by wrapping heat-generating light bulbs (not LED) below the foliage of the covered plants. Take care not to have bulbs burn the bark or branches.
• Remove sheets or blankets in the morning after the frost thaws. Dormant plants can be brought out of dormancy by keeping the plant covers on and trapping the heat during the day. Actively-growing plants are more likely to suffer frost damage than dormant plants. Frost cloth can be left in place for several days without harming the plant.

6. What to do after a frost

Did your plants suffer frost damage? Don’t prune them right away. The damaged limbs and branches protect the plant from further frost damage.

Before pruning, wait until the danger of frost is past in the spring and you begin to see new growth. Prune back to just before where the new growth begins. The plant may have suffered extreme damage and died if no growth is noticed. Cut it back low into the plant to see if any life remains. Read the complete guide to pruning peppers, tomatoes, and eggplants after winter here.

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Article Index:

• How cold does it need to be to freeze?
• What to cover in a freeze and what not to cover during a freeze
• Frost Tender Vegetables: Killed or damaged by a light freeze
• Frost Tolerant Vegetables
• Cold-Hardy Vegetables
• Which Landscape Plants to Cover During a Freeze
• Which Flowers to Cover During a Freeze

How cold does it need to be to freeze?

Freezing temperatures occur when the mercury dips to 32°F (0°C) or below. However, your garden’s microclimate might differ from the general forecast. That’s why paying close attention to the weather and regularly monitoring your yard is essential.

I use a weather station and a minimum/maximum thermometer to keep track of temperature variations. Sometimes, conditions in your garden can be colder than your phone’s weather app predicts. By staying alert to these differences, you’ll know precisely when to cover and protect your plants from unexpected frost.

• Light freeze: 29°F to 32°F (-1.6°C to 0°C). Tender plants are often killed.
• Moderate freeze: 25°F to 28°F (-3.88°C to -2.22°C). Causes damage to many plants.
• Severe freeze: 24°F (-4.44°C) and colder. Causes heavy damage to many plants.

What to cover in a freeze and which plants survive frost

Cold weather often signals the end of the life cycle for many annual plants. Crops like melons, beans, squash, and cucumbers can’t tolerate cold conditions and will die when temperatures drop, so you’ll need to replant them in the spring.

However, some tender perennials—such as peppers, tomatoes, eggplants, and basil—can continue to produce and grow if protected from freezing temperatures. In warm-climate areas like the low desert of Arizona, shielding these plants from freezes can prolong their growing season. In this blog post, learn how to protect your plants from frost and freezing temperatures.

Frost Tender Vegetables: Killed or damaged by a light freeze

Harvest before cold temperatures:

Beans, Corn, Cucumber, Melons, Okra, Pumpkins (may continue to ripen after a frost, but storage life will be decreased), Roselle, Sesame, Squash, and Sweet Potatoes (harvest before soil temperature goes below 50°F [10°C]).

Cover during a freeze to protect and prolong the growing season:

Basil, Eggplant, Ground Cherry, Peppers, Tomatillos, and Tomatoes (if prolonged freezing temperatures are expected, harvest tomatoes and allow them to ripen indoors). Learn more about how to turn green tomatoes red in this guide.

Frost Tolerant Vegetables

Frost Tolerant — withstands light and short term freeze (28°F to 32°F) (-2.22°C to 0°C)

Beets, Carrots, Cauliflower, Celery, Chard, Jeruselum Artichoke, Lettuce, Onion, Parsnip, Potatoes, Radish, Rutabaga, Strawberries (temperatures below 28°F (-2.22°C) will harm the blossoms), and Turnips.

Cold-Hardy Vegetables

Cold-Hardy — withstands moderate freezing temps (24°F to 28°F) (-4.4°C to -2.22°C) for short periods

Bok Choy, Broccoli, Brussels Sprouts, Cabbage, Chinese Cabbage, Kale, Kohlrabi, Leeks, Mustard Greens, Peas, and Spinach.

Which Landscape Plants to Cover During a Freeze

Many tender landscape plants will recover from light frosts but have unsightly damage if you don’t cover them. Covering tender landscape plants during a freeze may prevent damage. Remember, don’t prune frost-damaged plants until after the danger of frost has passed in the spring. Learn more about protecting citrus from freezing temperatures in this guide.

Frost-tender landscape plants:

Cover these plants during a freeze to prevent damage:

Frost-tender landscape plants include (but are not limited to) bougainvillea, some cacti, cape honeysuckle, coral vine, ficus, hibiscus, lantana, natal plum, myoporum, pygmy date palms, succulents, tropical plants (avocado, banana, guava, etc.), and yellow bells.

Which Flowers to Cover During a Freeze

Some flowers, including my favorite cool-season hardy annual flowers, aren’t bothered by mild frost events and don’t need to be covered. Others, however, should be covered if you want to overwinter them.

Frost-tender flowers:

Cover these plants during a freeze or remove plants before the weather cools.

Frost-tender flowers include (but are not limited to) ageratum, amaryllis, angelonia, begonia, calla lily, canna, celosia, coleus, cosmos, dahlia, four-o-clock, freesia, gazania, geranium, gomphrena, impatiens, lobelia, marigold, nasturtium, petunia, purslane, sunflower, tithonia, toothache plant, verbena, vinca, and zinnia.

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Would a greenhouse get too hot in Arizona?

How many months of the year could I use the greenhouse?

This article discusses the benefits of having a greenhouse (even in a hot summer climate), the challenges to consider, and the best ways to make the greenhouse a productive space during the year’s hottest months. 

Benefits of having a greenhouse

• Extends the growing season, whether in cold or warmer weather.
• The ability to control the environment, including sunlight, temperature, humidity, and ventilation.
• Protection from the elements.
• Little or no damage from insects, birds, and other animals.
• Increased water efficiency.
• Central location for seed starting and gardening supplies.
• Place to implement hydroponics or other methods.

Challenges with having a greenhouse in Arizona and other hot summer climates 

Historically, greenhouses have been used to trap heat. However, during the summer heat, greenhouse temperatures can surpass 150°F (65.6°C), which is too hot for plants. High winds during the monsoon and windy seasons also present a challenge. 

Choosing the best location for your greenhouse

Typically, a greenhouse is placed in an area with the most sunlight. However, in a hot summer climate, taking advantage of locations that offer natural shade is crucial.

Here are a few considerations about where to position your greenhouse:

• Look for locations in your yard that receive shade during the summer naturally. Consider how the sun exposure or shadows will change throughout the year.
• Level ground for the greenhouse foundation. Consider installing a cement pad.
• Protection from the elements. Placement near a house or fence can help. It is also essential to secure or bolt the greenhouse to the foundation. 
• Proper drainage. Ideally, the land surrounding the greenhouse is sloped so that water will drain away from your foundation. 
• Access to electricity and water. Plumb or put these in place before you add a foundation or cement pad. 
• Convenience. Someplace you can access easily.

What to consider before purchasing a greenhouse

Greenhouses come in various shapes, sizes, and use of materials. Available types include traditional, hoop houses, lean-to’s, cold frames, polytunnels, and attached solariums.

Considerations for greenhouses in hot summer climates: 

• Available space. Most people with greenhouses wish they had made them larger. Choose the largest size your space and budget will allow. 
• Design. Do you like the look of it? 
• Cost. What’s your budget?
• Durability. Arizona has severe winds during the monsoon season.
• Material type. A galvanized steel or aluminum frame (for durability) with thick polycarbonate panels (for good light diffusion and insulation) could be an effective solution for a hot summer climate. 
• Height. Adding vertical space can increase the available space for storage and ventilation.  
• Ventilation. Roof vents with (automatic) openers. 
• Misting systems and accessory availability.
• Quality of construction. Insulation of greenhouse with rubber seals, types of windows, etc.

How to keep a greenhouse cool in hot summer climates

Each method will only partially bring down the heat, but combining techniques will bring the temperature down and make the greenhouse usable throughout the year.

• Ceiling fan and circulating fans for air movement.
• Louver (manual and automatic) windows that can be opened or closed depending on temperatures.
• Interior and exterior shade cloth. 
• Tint the windows, just like you would a car. While these other strategies reduce the temperatures by 5-10°F, this method can reduce it by more than 30°F.
• Use a swamp cooler.  

Greenhouse management tips for a hot summer climate

Once you have a greenhouse, a few essential practices will help ensure your greenhouse is a place where plants thrive. 

• Like a garden, plan on spending time in your greenhouse daily to monitor the temperature and plant health. Problems will be easier to manage if you catch them when they are small. 
• Measure the indoor temperature and humidity. Learn which methods for cooling (or heating) the space are most effective. The goal is to maintain the inside temperature between 65-85°F (18-29°C). Try to avoid wide temperature fluctuations. 
• Keep a greenhouse journal: record germination times and temperatures to help you learn from your experiences. 
• Keep it clean. Sweep up or vacuum messes and debris. 
• Don’t overload your greenhouse. Good airflow is crucial for plants.
• Don’t bring pest-damaged or diseased plants into the greenhouse; they may spread those issues to other plants. 
• During the hottest months, you may need to provide additional lighting for plants if the light is blocked by shade cloth.  
• Avoid standing water. Use layers of gym-style pads and rubber mats to drain the moisture out of the building. Water seedlings from the bottom and drain off extra water. 
• Keep the door closed. This helps maintain the temperature and humidity levels and keeps insects out. 

Thank you to Larry Burnett for contributing to this post. 

Larry Burnett is a retired Administrator from Banner Health and a Partner from KPMG. Larry has lived in Arizona since 1984 and gardened here extensively. 

He is a Master Gardener through the University of Arizona and a mentor for Master Gardener students. His favorite time of the day is when he is outside in his greenhouse, garden, and flower beds. Here’s a link to Larry’s Jansen Greenhouse, featured in this article.

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A bulb on the top center stalk of your onion means it has begun the process of flowering and making seeds. This is called “bolting,” which is terrible news for onion growers.

What is bolting?

Bolting is the term that describes when a vegetable plant starts to seed or flower before it should. When onions bolt, the bulb part of the onion stops growing and will not mature further. The energy that would make the onion bulb is now directed towards making the flower stalk. 

Onions and shallots are biennial crops, which means that they grow the first year and flower the second year. When an onion or shallot forms a flower in the first year, it is called bolting.

Why do onions bolt?

An onion bolts in response to stress. Stress can happen in several ways: too hot, too cold, not enough water, or too much water. Temperature fluctuations can also cause onions to bolt.

Swings in temperature may cause the onion to think it is in the second year of growth when it is supposed to flower.

For example, warm temperatures followed by cool weather can encourage onions to go dormant. Once warm temperatures return, the onion may believe it is beginning its second growing season and produce seeds. 

The onion reacts to the stress by putting its energy into reproducing and making seeds.

What should I do when my onions bolt?

• Harvest and use (or preserve, see preserving tips below). 
• Cut off the flower on top, or cut the entire bolting stem, so the onion stops producing seeds. (This won’t restart bulb growth.) You can leave the onion in the ground for a few weeks. The onion won’t continue bulbing or get any larger, but it will “keep” in the ground and can be used later. 

• Do not wait to harvest until the onion leaves turn brown and fall over (as you do with onions that don’t bolt). Bolted onions may rot or become fibrous if left in the ground too long.
• Leave a couple of bolting onions to flower until they produce seeds. Save the seeds to plant next season.

How do I preserve bolted onions?

Use bolted onions right away, just as you would other onions. Bolted onions will not store well, and you need to preserve them differently than onions that did not bolt.  

Here are a few ideas for ways to preserve bolted onions: 

• Chop and freeze.

• Cut up the onions and dehydrate them. Use dehydrated onions whole, or process them into onion powder. Store the dehydrated onions whole for the most robust flavor, and then blend small amounts for powder. 

• Slice onions and freeze dry them. (This is my FAVORITE way to preserve onions.) Freeze-dried onions can be stored and used “as is” or processed into a powder. Looking for more information about freeze-drying? Read this post, Freeze Drying Tips for Beginners.

If you would like to learn more about freeze drying, read Freeze Drying Tips for Beginners.

What can I do to prevent onions from bolting next time?  

You don’t control the weather or other outside conditions that may cause onions to bolt. However, there are a few ways to help prevent bolting in the future. 

• Choose onions suited to your area. Onions are typically grouped into short, long, and intermediate day onions. Use this map to help determine which type to plant.
• Plant at the correct time. Use your local planting guide to determine when to plant. 
• Onion sets (small bulbs) tend to set more frequently, especially in hot climates. Grow onions from seed or transplant instead. 

If you would like more information about how to grow onions, read this blogpost.

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Garden Troubleshooting Guide: How to Identify & Solve Common Garden Problems

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Garden Troubleshooting Guide: How to Identify & Solve Common Garden Problems (cont.)

Garden Troubleshooting Guide: How to Identify & Solve Common Garden Problems (cont.)

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