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Thursday, June 30, 2011

Dealing with Plant Wilt

Wilting plants often grab your attention when you patrol your garden, but the cause and control are often misunderstood. So here's a quick quiz. Which of these common plant issues can cause a plant to wilt: not enough water; too much water; not enough sun; too much sun?

My guess is you picked out not enough water and too much sun right away, but those are only two of the potential culprits. In reality, all four can cause plant wilt, in addition to disease, poor root growth, low temperatures, and incorrect fertilization.

During the heat of summer, many garden plants show their discomfort by sagging and losing the rigidity in their stems and leaves. It makes the plant look sad and evokes the same emotion in gardeners. Wilting is caused by a reduction of water in the plant cells. Many people know this so the first reaction of many gardeners is to add water to "make the plant better" whenever they see it wilting. Without full analysis you may actually harm the plant with that course of action.

A wilting tomato plant

Plants require water for virtually every function of life. It cycles through the plant cells in very efficient machinery. Little cells in the leaves (the stomata) open and close to regulate the flow of water vapor and carbon dioxide. Through transpiration the cells open, releasing water vapor from the leaves. That creates a pressure imbalance so more water is drawn up from the roots to replace it. That's how nutrients and water move from the roots to the rest of the plant.

When a plant senses a harsh and potentially harmful condition, like excessive sunlight and heat, the stomata will close, effectively shutting down the conveyor system and no more water flows to the plant structure. The result is what we interpret as wilt. This is not necessarily a bad thing. The plant is in protection mode. It's trying to keep water in its cells by limiting what it loses to the air. Once conditions improve, like less heat, the stomata open up again and the flow resumes. The plant is erect again.

Wilting is a perfectly normal reaction to the stress of the day. Many plants droop in the afternoon and pop back into shape as the sun moves lower in the sky. It doesn't harm the plant and as long as other conditions are fine, there's nothing you should do to "fix" it.

That's why analysis is needed with wilting plants. Stick your finger in the soil during the hot summer day when you see wilting. If the soil is still moist, or at least not bone dry, it is normal and the plant is just taking a break from dry and hot air. There's enough moisture in the soil for the roots, the plant is choosing to shut down transpiration to avoid excessive moisture loss. No extra water from you is needed and the plant will bounce back later.

If your finger reveals a complete lack of moisture, it may be time to water. That won't reverse the wilt immediately, but will add much-needed water to the soil. The plant probably closed its stomata normally because of the hot day and that same heat dried out the soil. When it's ready to resume transpiration the stomata will open and it will begin drawing moisture from the soil. In that case, watering when you see wilt and dry soil can help.

Watering dry soil helped the same plant bounce back

If your finger reveals a soggy or over-watered soil, you may have identified a cause of the wilting. For transpiration and the flow of water through the plant to work effectively, the roots need to be functioning properly. Roots that are drowning in water may be damaged, killed, or at least adversely affected. The stomata may be open, but if the roots aren't capable of supplying moisture because they are struggling, the cell moisture imbalance will result in wilting. This is when watering makes a bad situation worse. Many houseplants that die from overwatering succumb to this cycle of the gardener watering because the plant is wilting.

Too little sunlight can cause a similar plant reaction. Some plants may wilt when they aren't receiving enough sunlight because stomata also play a role in photosynthesis. Watering wilting plants in the shade may be inducing a situation where you add too much water to the roots. In this case knowing your plants becomes important. Sun-loving plants shouldn't be planted in the shade.

If there isn't enough water in the soil and roots to replace what is lost through transpiration when the stomata do open again, the wilting can reach the point where the physical structure of the plant cells are damaged. In that case, watering will not reverse the wilting; the plant is not able to revitalize the damaged tissue. This is when the wilted leaves turn brown and die. If enough leaves and plant tissue is lost the plant will die.

Excessive heat and dry soil caused leaf damage in this pepper

Cold temperatures can also cause the same type of tissue damage. In the fall, cold nights cause wilting and eventually the cold causes cell damage. Brown leaves and dead plants mark the end of the season.

A couple other factors are over-fertilization and disease. When you apply too much fertilizer you can create an imbalance in the plant's growth rate forcing the roots and stomata to work themselves to death; the root structure may not be able to support the plant growth and the lack of water movement causes wilting.

Some plant diseases cause wilt (often seen in tomatoes); there are usually other signs associated with this type of wilt and sprays and powders that can help when you identify it. If your soil is good, your water practice is good, and the plant doesn't recover under cool conditions, the wilting may be due to a fungal disease. Researching the plant, and it's susceptibility to wilting diseases, can help you take appropriate control measures.

There are a few things you can do to reduce harmful wilting. The best control is maintaining consistent soil conditions. If an organically-enriched soil is constantly at an appropriate moisture level through efficient watering and mulching practices, the plant will have the water when it needs it.You won't need to worry about plant damage even when the plant looks stressed during the heat of summer.

Knowing your plants and selecting heat and sun loving plants for hot and dry conditions is good. Plants that have a natural tolerance to heat stress may show no sign of wilting even in extreme conditions. Xeric plants are in this category. Plant tags, plant catalogs, and online resources will often identify how much sun and how much water a plant requires. Matching the plant with the appropriate location is always the best planting practice.

Most importantly, don't automatically reach for the garden hose when you see wilting. In addition to the root issues I discussed above, spraying the leaves can cool the air temperature and cause the stomata to open. If there isn't enough moisture accumulated in the roots or soil, you will force the plant to lose water from its cells and that may be enough to cause irreparable damage.

Once you understand wilting and realize it's nothing that requires overreaction, you can relax and actually enjoy watching the natural process. Seeing a plant recover from the sad state of wilt to a fully erect display of health in just a few hours is an amazing thing.
Wilting plants often grab your attention when you patrol your garden, but the cause and control are often misunderstood. So here's a quick quiz. Which of these common plant issues can cause a plant to wilt: not enough water; too much water; not enough sun; too much sun?

My guess is you picked out not enough water and too much sun right away, but those are only two of the potential culprits. In reality, all four can cause plant wilt, in addition to disease, poor root growth, low temperatures, and incorrect fertilization.

During the heat of summer, many garden plants show their discomfort by sagging and losing the rigidity in their stems and leaves. It makes the plant look sad and evokes the same emotion in gardeners. Wilting is caused by a reduction of water in the plant cells. Many people know this so the first reaction of many gardeners is to add water to "make the plant better" whenever they see it wilting. Without full analysis you may actually harm the plant with that course of action.

A wilting tomato plant

Plants require water for virtually every function of life. It cycles through the plant cells in very efficient machinery. Little cells in the leaves (the stomata) open and close to regulate the flow of water vapor and carbon dioxide. Through transpiration the cells open, releasing water vapor from the leaves. That creates a pressure imbalance so more water is drawn up from the roots to replace it. That's how nutrients and water move from the roots to the rest of the plant.

When a plant senses a harsh and potentially harmful condition, like excessive sunlight and heat, the stomata will close, effectively shutting down the conveyor system and no more water flows to the plant structure. The result is what we interpret as wilt. This is not necessarily a bad thing. The plant is in protection mode. It's trying to keep water in its cells by limiting what it loses to the air. Once conditions improve, like less heat, the stomata open up again and the flow resumes. The plant is erect again.

Wilting is a perfectly normal reaction to the stress of the day. Many plants droop in the afternoon and pop back into shape as the sun moves lower in the sky. It doesn't harm the plant and as long as other conditions are fine, there's nothing you should do to "fix" it.

That's why analysis is needed with wilting plants. Stick your finger in the soil during the hot summer day when you see wilting. If the soil is still moist, or at least not bone dry, it is normal and the plant is just taking a break from dry and hot air. There's enough moisture in the soil for the roots, the plant is choosing to shut down transpiration to avoid excessive moisture loss. No extra water from you is needed and the plant will bounce back later.

If your finger reveals a complete lack of moisture, it may be time to water. That won't reverse the wilt immediately, but will add much-needed water to the soil. The plant probably closed its stomata normally because of the hot day and that same heat dried out the soil. When it's ready to resume transpiration the stomata will open and it will begin drawing moisture from the soil. In that case, watering when you see wilt and dry soil can help.

Watering dry soil helped the same plant bounce back

If your finger reveals a soggy or over-watered soil, you may have identified a cause of the wilting. For transpiration and the flow of water through the plant to work effectively, the roots need to be functioning properly. Roots that are drowning in water may be damaged, killed, or at least adversely affected. The stomata may be open, but if the roots aren't capable of supplying moisture because they are struggling, the cell moisture imbalance will result in wilting. This is when watering makes a bad situation worse. Many houseplants that die from overwatering succumb to this cycle of the gardener watering because the plant is wilting.

Too little sunlight can cause a similar plant reaction. Some plants may wilt when they aren't receiving enough sunlight because stomata also play a role in photosynthesis. Watering wilting plants in the shade may be inducing a situation where you add too much water to the roots. In this case knowing your plants becomes important. Sun-loving plants shouldn't be planted in the shade.

If there isn't enough water in the soil and roots to replace what is lost through transpiration when the stomata do open again, the wilting can reach the point where the physical structure of the plant cells are damaged. In that case, watering will not reverse the wilting; the plant is not able to revitalize the damaged tissue. This is when the wilted leaves turn brown and die. If enough leaves and plant tissue is lost the plant will die.

Excessive heat and dry soil caused leaf damage in this pepper

Cold temperatures can also cause the same type of tissue damage. In the fall, cold nights cause wilting and eventually the cold causes cell damage. Brown leaves and dead plants mark the end of the season.

A couple other factors are over-fertilization and disease. When you apply too much fertilizer you can create an imbalance in the plant's growth rate forcing the roots and stomata to work themselves to death; the root structure may not be able to support the plant growth and the lack of water movement causes wilting.

Some plant diseases cause wilt (often seen in tomatoes); there are usually other signs associated with this type of wilt and sprays and powders that can help when you identify it. If your soil is good, your water practice is good, and the plant doesn't recover under cool conditions, the wilting may be due to a fungal disease. Researching the plant, and it's susceptibility to wilting diseases, can help you take appropriate control measures.

There are a few things you can do to reduce harmful wilting. The best control is maintaining consistent soil conditions. If an organically-enriched soil is constantly at an appropriate moisture level through efficient watering and mulching practices, the plant will have the water when it needs it.You won't need to worry about plant damage even when the plant looks stressed during the heat of summer.

Knowing your plants and selecting heat and sun loving plants for hot and dry conditions is good. Plants that have a natural tolerance to heat stress may show no sign of wilting even in extreme conditions. Xeric plants are in this category. Plant tags, plant catalogs, and online resources will often identify how much sun and how much water a plant requires. Matching the plant with the appropriate location is always the best planting practice.

Most importantly, don't automatically reach for the garden hose when you see wilting. In addition to the root issues I discussed above, spraying the leaves can cool the air temperature and cause the stomata to open. If there isn't enough moisture accumulated in the roots or soil, you will force the plant to lose water from its cells and that may be enough to cause irreparable damage.

Once you understand wilting and realize it's nothing that requires overreaction, you can relax and actually enjoy watching the natural process. Seeing a plant recover from the sad state of wilt to a fully erect display of health in just a few hours is an amazing thing.

15 comments:

  1. I made a big mistake by watering my wilted tomato plant yesterday and today. I fear that I may have just killed my plant. Its been wilted for 2 days now and I watered it again today and just now realized I made the wrong mistake. I'm really hoping that it will recover. Do you know what the chances are it will if I let it be for a while?

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  2. Before you water it again, stick your finger deep in the soil and check the moisture; you don't want to drown the plant with too much water. If the soil is moist, not soaked, and the plant is still wilted, it may have suffered cell damage and the wilted part won't recover. That doesn't mean the plant is dead, just portions of it. If the main stems stay green, they may recover and send out new growth. If the plant is alive you can continue watering it as needed, though not as much as when it was filled with leaves. If you can shade the plant during the recovery process it might help. A wilted plant that is alive will still maintain some rigidity and have some green; a dead plant will turn brown and shrivel. Observe your plant over the next few days and look for improvement before assuming the worst.

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  3. Great blog post..very informative thanks....

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  4. I didn't realize how cold it got last night and now my tomato plants are wilted but still green. Soil is still moist as we just had some rain. Any ideas as to what I should do. I've covered them with a light breathable material.

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  5. If plant wilt is caused by cold/frost conditions, the leaves won't recover; there is probably damage in the plant cells. As long as the plant is still alive and not too damaged it will be okay and send out new growth soon. Continue to cover with fabric or row covers when the temperatures cool down. The soil will probably be too cool for tomatoes right now and it may take awhile to notice growth. Keep the soil moist, not wet, (use mulch to help) and keep them covered until the weather warms the plants and soil.

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  6. I have a bell pepper plant that U'm sure I over-watered initially, the wilting has gotten better but the leaves are curling, turning yellow and black. Is there anything I can do? I live in Las Vegas, I've been allowing full sun.

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  7. It sounds like you might have more going on than overwatering. Dying leaves that are damaged by overwatering can yellow and then turn brown when dying, but your problem could be blight or a bacterial or fungal disease. Often diseases are introduced when water splashes on the plants and weak plants can be very susceptible; wilted plants from overwatering can be weak. Verticillium and Fusarium wilt could be possibilities too. Insects like aphids and thrips can cause curling. Take a close look at the plant. Are all the leaves affected? Is there new growth that looks normal? Are some leaves curled but not discolored? Can you see little insects? If you can see insects and some leaves are green and healthy, you can treat with an insecticide and save the plant. If the entire plant is infected and nothing looks normal, pull the plant and discard it. If only part of the plant is affected you can prune off damaged areas and water normally to see if you can save it. You can check with the Cooperative Extension office in Clark County for more specific info for plants in Vegas. Good luck.

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  8. Thanks for this informative post. My tomato plants wilted when I transplanted them into bigger pots, with a soil that has great drainage, but also retains moisture. Too much water? Not enough? Growing too fast? Not sure yet, but thanks for explaining the processes.

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  9. You're welcome. Transplanting often damages roots and almost always stresses plants. A stressed plant often responds by wilting. Transplanting in hot conditions worsen the stress. Letting the bare plant rest too long in dry air while preparing the new pot is a common cause too. Many times wilt will improve with time. A good soaking is recommended after transplanting to give plants as much water as they can absorb and usually that's enough to reverse the wilt. After the initial boost, normal watering patterns should be followed. If the wilt continues check the moisture level of the soil by putting your finger in the soil to root level. If the soil is still saturated that can explain the wilt. Tomatoes can be quite resilient and even if there is some cell damage new growth should appear soon.

    ReplyDelete
    Replies
    1. I transplanted my tomatoes and plants in the heat of the evening (I live in Southern Utah so probably around 80 degrees) and they have wilted. Two questions: 1- How long will it take the plants to look normal if conditions are right (have enough water, sunlight, etc.)? 2- Would it be advisable to prune off some of the more withered leaves if the stalk is still green?

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    2. Transplants should begin to look "normal" after two or three days in their new location. Minor wilting can improve in a matter of hours. Severe wilting can lead to cellular damage and those parts of the plant will likely never recover. If wilted and withered branches and leaves have not recovered after a day of normal watering, you can consider pruning them off. That helps clean up the plant and quickens the healing process of the plant at the prune site.

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  10. I forgot to water my tomato and basil starters over the weekend. I have the plants under grow lights and immediately turned the light off while I soaked the soil. How do I know if the plants are dead? There is no browning but the leaves are in really bad shape. Thanks for the info posted above.

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  11. One or two missed days of water may not be a death sentence. For young plants you can usually tell if they're dead pretty quickly. The little tender stalk will shrivel and collapse in a day or two and the leaves will turn brown. If the plant stays erect, give it a little time and see if new green growth emerges. Be careful that you don't go to extremes to try and correct lack of watering. Soaking the soil and leaving the roots to drown in too much water will kill young plants. Also they need light; flourescent grow lights don't produce excess heat so turn the light back on. Keep the soil moist, not wet, so you may not need to water as often as you think. Good luck.

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  12. Thank you for the information. It has helped me to understand a little better. We just transplanted some tomato plants, pepper plants, cucumber plants, zuccini plants and cantalope plants. We planted them in the early morning before it started to get hot. They are wilting now and I think it's just from the heat. We did give them a good drink right after planting them..and they did look perky this morning. My question is how often should I water new transplanted plants? I live in Tooele, UT and it gets very windy here and one day it can be cool..like 70 and then the next day it's over 80 close to 90 degrees and by time June hits it stays in the 90's. This is our third season planting and as of yet we haven't had success. Our soil is kind of sandy.This year we fertilized the dirt in the early spring with horse manure. We did put a bark mulch around each of the plants to help the plants moist. So, have we done the right things for these plants so far? We really do want success this year. Thank you.

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  13. Just to follow up, because I answered Camille on my facebook page, new transplants should be watered often in hot, dry, windy areas. Sandy soil will require watering more often than clay soils. Amended soils will require less watering than unamended soils. The soil should remain consistently moist, not saturated, until the new plants begin developing a good root structure (usually in a week or two). I also don't recommend bark mulch for vegetable gardens. Straw or dried grass works better because you can till it in at the end of the season and it becomes a soil amendment.

    ReplyDelete