We’ve received quite a few questions during the recent heatwave about how to revive stressed plants, and we are more than happy to help! Here are some popular inquiries and answers to prepare for future temperature extremes.
1. How do I help my lawn? I am watering it every day, but it’s still getting fried!
Turf grass has a very shallow root system and at the temps we recently saw, water evaporates quickly from the soil. In spite of regular watering, your grass probably got sunburned. Although our Northwest grass blends are not bred to handle these conditions, your grass should recover if you continue regular watering and fertilizing for the season.
2. My hydrangeas are taking the worst of the heat. Any tips for recovery?
Hydrangeas really struggled. It was painful to watch! As long as the plants were kept well watered, most of the plant damage may have been limited to the flowers which turned brown or wilted in the heat. Clip off spent flowers by cutting just above the leaf that is below the flower bud and fertilize. If your hydrangea foliage is also damaged, it may be sunburned (crispy or brown around edges). Depending on the amount of total damage, your plant will eventually recover from severe sunburn, but may not rebound from extreme drought.
3. My red currant has curling leaves even though it was watered deeply every day during the heat wave.
Red currant plants prefer partial shade or at least protection from the hot sun, and will certainly show a sunburn after these past few days. As long as the plant did not get too dry, the burnt leaves will slowly fall off as the plant grows new ones; remove any foliage that is more than 50% damaged and lightly fertilize to help it recover. The next possible issue to watch for is spider mites; this heat may have caused a pest population explosion and stressed plants may be “sitting ducks” for an infestation. Red currants are susceptible to mites, so watch for more yellowing/browning leaves or find webbing on leaves and/or branches. Bring leaves in a baggie into the garden center for confirmation and treatment options.
4. My blueberries got toasted even with daily watering. How do I care for them now?
Blueberries have a very shallow, fibrous root system that is very vulnerable to drying out, especially when bearing fruit. If your plants are newly planted (1-2 years in the ground), they may not recover. Prune back the plants to remove some of the top-most growth and take off this year’s berry crop to reduce the plant’s energy requirements. Give them a light application of kelp meal as a top dressing and then mulch over the roots with bark, compost, etc. to reduce evaporation from the soil. Continue watering normally and give the plant time to rebound. Evaluate this fall and consider planting new blueberries if they don’t seem to be recovering.
5. My begonias have suffered! Tips to help them recover?
Begonias are tricky in this kind of weather! They are so sensitive to rotting when they get too much water, but can’t stand intense sun either. If they have been scorched, it’s best to cut back the leaves that look more than 50% damaged and remove the flowers to help the plant recover with less of a burden. Give them a diluted organic liquid fertilizer, but make sure they are well hydrated before feeding. If possible, provide them with extra shade during the most intense sun conditions. If you have accidentally overwatered them and they are in permanent wilt, unfortunately, there is not much hope for recovery and it may be time for replacement.
6. I watered the heck out of my perennial every day, but it’s still drooping. Will it get better?
We went out in the hottest part of the day yesterday to see most of the mature landscape plants literally melting, even the toughest lavender! Plants partially welt as a technique to conserve water and reduce moisture loss from their leaves when exposed to intense sun, even if they are well hydrated. In most instances, the plants fully recover after the sun has set or once they are in shade without additional water. This morning, the lavender looked perfectly normal again!
7. Two thirds of my cucumber plant is now wilted. Can I revive it?
If two thirds of the plant is wilted or damaged, it may not recover, but there is still plenty of time left in this growing season to replant. If you start seeds in the ground, you could still grow cucumbers this year!
8. My hibiscus was burnt to a crisp. The stems are okay, though! Is it salvageable?
It sounds like your hibiscus will recover, but will probably drop most of the damaged leaves, abort any developing flowers, and look sad for a while. Give it a little fertilizer and trim off the worst-looking foliage now. Continue normal watering or maybe even a little less frequently if it has much less foliage to maintain.
9. My weigela is in rough shape. It’s in a large pot and gets afternoon sun. A large tree that used to offer some shade was cut down due to ice storm damage, so the sun is relentless. Will it help if I trim off the brown stems and transplant it into the ground?
Your weigela looks like it got pretty burned and too dry. I bet it can recover in time, but it might be better if planted in the ground. Go ahead and cut it back by about 1/3 (you will not get flowers this year if it has not bloomed yet), plant it during a cool part of the day with these hot weather planting techniques. Provide temporary shade for the first 2 weeks after transplanting, water deeply every 2 days for the first 2 weeks, then begin to back off 1-2 days between waterings each week.
10. All new growth on my tomatoes is fried. How should I proceed?
Although we hope for good summer heat for our tomatoes to ripen, sustained temps over 95 tend to hinder fruit set and can even sunburn developing tomatoes. I noticed damage and wilting of new growth on a few of my tomato plants, mostly ones that have been planted for less than a month. All my tomato cages had been draped with shade cloth, but the wind had blown the cloth off of one tender plant that is now about one third burned. All my tomato plants were in a complete wilt during the hottest part of the afternoon yesterday, but only one seems to have sustained permanent damage to the top-most new growth. This morning, I pinched off the wilted tips and gave my plants a light liquid kelp meal feeding, which boosts potassium levels and helps plants recover from stress. If you do the same, I bet your plants will rebound after a few weeks!
11. My Daphne burkwoodii got sunburned leaves. Do I clip them off or let them fall off on their own?
Sunburned leaves will eventually fall off on their own, but you could remove any leaves that have more than 50% damage now to improve the plant’s overall look. You can also help the plant by fertilizing to support a flush of new growth.
12. Some of my newer lupines are wilting away and flowers are getting fried. What can I do?
It sounds like your lupine plants were newly planted this year. New plantings are especially vulnerable to extreme heat and sun, and the stress can be multiplied when plants are in bloom. Be sure to not overwater your plants in the ground; a deep soaking every few days is preferred over daily sprinkling. A layer of mulch at least 2-3 inches will help keep the moisture in the soil and reduce evaporation. You may need to cut back the flower stock and some of the crispy leaves, lightly fertilize, and allow it some time to regrow.
13. My new trees and perennials are still in nursery pots. Should I wait until fall to plant?
It depends how many plants you have, how large your project area is, the degree of sun exposure, and your summer plans! You may choose to keep your plants in containers (even pot up some of the smaller ones into larger pots), but remember that they will need to be watered pretty much daily until they get planted. If your project area is relatively small and can be provided temporary shade protection during extreme heat, you may choose to go ahead with planting now. Be sure to follow these hot weather planting steps.
14. My knockout roses are fried despite watering deeply each morning during the heatwave.
In spite of your good watering, your knockout roses had probably never experienced anything like the recent temperatures and got sunburned. You can cut back the plant to remove the damaged parts and fertilize. Even if you prune it back hard, it should grow back better than ever and bloom in about 6 weeks or so. That will still leave you with several months to enjoy this year’s flowers!
15. Should I water frequently throughout the day or only once or twice during a heatwave?
Plants in containers may need to be watered more than once daily, depending on the container size and degree of sun exposure. The best time to water is in the early morning so plants begin the day fully hydrated. When watering in-ground plantings, it is better to provide a deep soaking every few days than frequent light watering. Mulch containers and other plantings to reduce moisture evaporation.
16. Can I rehabilitate severe sunburn on conifers and pines (evergreens)?
Severely burned conifers and other evergreens may need to be removed or replanted; they do not recover easily and will show their damage for many years (they don’t drop leaves each season). Depending on the location of the sunburned area, some light pruning may help remove the worst looking foliage, but be careful not to prune into bare branches, as many conifers will not regrow from such old wood.
17. If potted plants look completely dried out and even feel crisp, is there anything to do? I’ve been watering!
Potted plants that are completely dried out and crispy could either just have gotten fried by the sun’s intensity or have potentially been overwatered. Sun-scorched plants can be cut back and fertilized and should recover with time (planting in the ground would be even better!). However, root rot is usually fatal. It is a delicate balance to keep plants well hydrated, but allow the roots to dry out enough to function properly. Plants that are kept constantly wet can develop root rot, which eventually causes the plant to wilt or show other signs of stress as the roots collapse and can no longer sustain growth. Should we have this kind of extreme heat again, it’s best to move containers to a shaded location or even inside. If you cannot move them, provide protection with tomato cages draped with shade cloth, or use recycled umbrellas attached to bamboo stakes; stick them into each pot for individual shade from the midday sun.
18. My nandina got a little scorched. It’s not in terrible shape, just some of its upper leaves turned brown. I thought I would just cut the brown leaves off. Any suggestions?
The nandina just got a sunburn. It will drop off the worst leaves in time and recover, but you can trim them off yourself if you prefer not to wait. Follow up with a light, all-purpose fertilizer to help with new growth.
19. My fiddle leaf fig got too hot during a power outage! It still has a small amount of leaves.
FLF are sensitive to temperature changes (and just plain drama queens)! Pick up the pot to feel how heavy the plant is; if heavy, don’t water it, but give it a nice thorough soaking if it’s light. You can also lightly mist the leaves and give it some Joyful Dirt fertilizer the next time it needs to be watered. My plants have been struggling for light since my blinds and curtains are closed. I’ve added a few LED grow lights to some of the darkest rooms to help them out.
20. My monstera was accidentally left outside and is burned. What should I do? Is it RIP?
Ouch! The tender, large foliage of your monstera must have taken quite a hit! Hopefully, you caught it outside before it spent too long in 100+ degrees and it has just gotten an extreme sunburn. You have probably already given it a good drink and trimmed off the worst looking leaves; that’s about all you can do right now, but there is always hope where plants are concerned. Be careful not to overcompensate by watering too much or too often, especially now that you have removed some of the foliage. Next time it is ready to be watered, fertilize it with something delicious like Joyful Dirt, which has beneficial microbes in addition to nutrients that should assist with recovery. As long as the crown of your plant did not sustain major sun damage, it should be able to push out new leaves to quickly recover to its former glory after a few months.