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How To Revive Sick Cannabis Plants

When your cannabis plants are sick and stressed, it’s important to immediately identify the problem. That’s when the real process of reviving your cannabis begins. Here’s what to do to help your plants recover and thrive after a major setback.

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Your plant is wilting, you notice the leaves turning yellow or forming unsightly spots, or maybe it’s refusing to grow altogether. There are many reasons why cannabis plants can become sick, from issues with watering to pest infestations, inadequate lighting, heat stress, and more.

No matter the reason for your plant’s sickness, the first thing you’ll want to do is diagnose the problem. When you have addressed the cause(s) of your plant’s condition, you obviously want to revive it as fast as possible. Here are some things you can do to help plants recover from infestations, illness, and more.

PROBLEMS IN YOUR GROWING ENVIRONMENT

If your plant appears to be dying or suffering hard, it is unlikely that a minor issue is occurring. Most of the time, a rapid descent in the health of your plant signals a fundamental issue or invasion. This can involve problems with environmental conditions, microscopic infestations, and other culprits.

CHECK TEMPERATURES AND HUMIDITY IN YOUR GROW ROOM

If you’re growing indoors, the first step to reviving your plants is to check the temperature and relative humidity of your tent or grow room. The ideal temperature for cuttings and seedlings is between 20–25ºC. As the plants get older, they can tolerate a bit more, up to 28ºC. Everything above this is excessive and causes stress, which will make it much more difficult for your plants to recover.

Likewise, the humidity levels of your room must be kept within a certain range depending on the phase of growth. An optimal humidity level for flowering plants is 40–50%. Plants in the vegetative growth phase can tolerate a more humid environment, from 40–70%. If the humidity is too high, you need to look into better ventilation for your grow space. A dehumidifier is the best, albeit expensive option here. Your sick plants will have a hard time recovering if their environment is not stable and optimal.

AVOID HEAT STRESS OUTDOORS

Despite cannabis loves plenty of light and warm temperatures, if you grow outdoors in the summer, heat stress and excessive sun can be a problem, especially for plants recovering from illness. If you have your plants in pots and they look stressed from too much heat, move them to a shadier location. Less heat and direct sun will make it easier for sick plants to get back up to strength.

LOWER YOUR LIGHT LEVELS

Cultivators normally keep their wattage levels as high as possible to encourage plants to grow faster. More light means the plant is working harder and will likely produce a greater yield. On the other hand, a plant that is working extra hard is more susceptible to deficiencies and other problems. One way to give your sick plant a break is to decrease the light intensity. Move your lights higher up and further away from your plants, or decrease the wattage.

When you grow indoors with your lights on a timer, you can also cut down on the daily light hours your plants receive. When you reduce the light hours for the vegetative phase to only 17 or 16 a day, this will give your plants more time to “rest” and recover.

FLUSH YOUR PLANTS

Many problems with sick cannabis plants can be due to overfeeding. When your plant can’t take up the nutrients that you provide, salts and minerals will accumulate in the soil over time. This will change the pH level at your plant’s root zone, making it more acidic—beyond the small pH window that cannabis has for healthy growth. As a result, your plant is not able to take in nutrients, even if they are present in abundance. When this happens, further feeding only makes it worse.

In almost all cases where your plants show signs of nutrient deficiencies or nutrient burn, you should give your plants a solid flush. Flushing means that you rinse out the excessive salts with pure, pH-balanced water to restore the optimal pH of the growing medium.

To flush your plants, drench the growing medium with water numerous times. It should be ample enough that liquid comes out from the bottom of the container each time. For example, if you grow in 7l pots, flush your plants with 14l of water. When you grow in soil, your water should have a pH of about 6.5pH. After the flush, you can begin giving nutrients again, starting with ½ or ¾-strength doses. You can slowly work your way up from here to avoid putting plants under any additional stress.

REPOT YOUR PLANTS

Repotting your cannabis plants into new, larger containers with fresh soil can also help bring them back to life. Choose a container that has plenty of room for the roots to grow. If your plant is severely damaged due to overwatering (root rot) or various fungi, consider trimming its foliage. When the roots have fewer leaves to support, they can recover faster.

KEEP PESTS AWAY

Plant infestations from spider mites, fungus gnats, fruit flies, and other insects are all too common when you grow cannabis. When you have finally gotten rid of the pests, you want to make absolutely sure that they don’t return. Pest infestations can really ravage a plant, so it certainly needs optimal care and time to be revived.

In terms of keeping the pests away, there are natural insecticides like neem oil that can be highly effective. You can even use it as a foliar spray, applying it to your leaves every 2 or 3 weeks. However, be careful during the flowering phase as you do not want the overbearing taste of neem oil on your buds! For fungus gnats, you can also set up yellow sticky traps, which will catch most of them.

Neem oil serves as a completely natural way to protect your cannabis plants against pests.

Neem oil serves as a completely natural way to protect your cannabis plants against pests.

SUPPLEMENTS TO HELP YOUR SICK PLANTS RECOVER

There are certain supplements you can give to your sick plants to reduce stress, support their development, and increase their resistance.

Compost Teas

For those growing in soil, compost teas are an excellent supplement to support the recovery of sick and stressed plants. Compost teas can make your plants grow faster and more robust, making them less susceptible to diseases and deficiencies. Some cultivators make their own compost teas at home, although they can also be purchased at most well-sorted grow stores.

Silica

Silica has properties that strengthen the cell walls of your plants, which makes it helpful for increasing their resilience. Furthermore, it makes certain minerals and nutrients more available while protecting the roots as well.

Seaweed

Seaweed contains minerals and other micronutrients, and has been shown to help reduce plant stress. While its mechanism is somewhat unknown, seaweed has long been part of the weed grower’s arsenal.

With the above tips, we hope you are able to revive your precious cannabis plants and make it to a hefty and healthy harvest.

In this guide, you'll learn how to help revive your sick and stressed cannabis plants after infestations, nutrient deficiencies, and much more!

Why is my whole plant wilting, curling, with tips turning black and leaves turning yellow?

Question: Why is my whole plant wilting, curling, with tips turning black and leaves turning yellow? Just flipped to the flowering stage. Plant is drinking less than normal.

Additional info: Grown in coco coir with Fox Farms nutrients. Have been growing this plant from a seed and was in veg state growing very well with CFL lights (6500k) 24/7. Very full and bushy plant with many leaves and smelled nice.

Switched to the flowering stage by changing the lights to 12/12 (2700k). Two days later, the plant leaves were drooping, curling inwards, drying out and tips were turning black. Other leaves were a bright green and now almost yellow.

During veg stage plant was getting PH’d water and a mixture of Grow Big and Big Bloom. On 5/9 plant got a mixture of Tiger Bloom and Big Bloom. Plants have always been watered with PH’d water but noticed as of recently it wasn’t drinking as much. As of 5/11, I have flushed the plant with PH’d water 3 times in case there was salt buildup. I have also hand sprayed the plant hoping it would help the very dry leaves that were close to dying. After all this, the plant looks worse today and hoping I can still save. Not sure what has caused it to start dying but please help.

Answer: This plant is showing classic signs of root problems like root rot. The fact that your plant is drinking less than normal also seems to indicate that there’s a problem at the roots. When the whole plant seems to just “deflate” overnight, it’s often caused by root problems. Heat can be a trigger (root bacteria love warm temps) and will also make this problem worse.

Root problems often hit growers in soil or coco coir soon after the flip to the flowering stage, especially with less powerful lights like CFLs. This is because plants use a lot more water when they’re receiving 24 hours of light a day. When you flip to 12/12 light for the flowering stage, it’s easy to overwater plants if you continue watering them on the same schedule.

It’s important to user proper watering practices throughout your grow.

If you think you may have root problems, there are two easy ways to deal with this.

1.) You can purchase Hydrogen Peroxide in 3% – 35% strength.

Mix 1 cup of 3% Hydrogen Peroxide with a gallon of water. For 35% strength Hydrogen Peroxide, mix one tablespoon to a gallon of water.

Water your plants with the mixture to kill any bacteria living in your root area. Unfortunately, hydrogen peroxide also kills good bacteria, which can protect your plant from future infections.

2.) (My preferred method) Conversely, you can start adding Hydroguard to your nutrient-water when you feed.

This will build up colonies of good bacteria that out-compete the bad bacteria and actually promote plant growth.

In addition, the beneficial bacteria will offer protection for those times when the temperature of the grow area rises at a time when you can’t control it. When I first got started with bubbleponics, I had a few tough bouts with root rot.

Over the last few years, I’ve tried many “good bacteria” products including the ($$$) Great White and Subculture B additives, but no product has ever worked 1/4 as good at maintaining healthy roots as super cheap, readily available Hydroguard.

My soil/coco coir / growing medium seems to stay wet no matter what

If the plant medium seems to stay wet no matter what you do, you may need better drainage. It may also help to move plants to a smaller pot until they get bigger and start drinking more.

Make sure that water drains freely from the bottom of your container (it’s recommended that you provide enough water to get at least 20% extra runoff every time you water your plants). You should see water coming out the bottom within a minute or two after watering. Then don’t water your plants again until the soil is dry up to your first knuckle.

For soil/coco coir grows, you generally only want to water the plant when the soil feels dry if you press a finger in it. You can also use the “lift the pot” method to decide when to water your plants (basically wait until your pot feels “light” since the plants have used up all the water). For other growing mediums besides soil, your watering method will vary, but if your plants are drooping and you’ve been feeding them a lot of water, it’s a good idea to cut back and see if that helps.

If your plants are already overwatered, you can try to increase airflow to help the water evaporate more quickly. You can also use a pencil to gently poke some air holes into the growing medium to provide extra aeration and oxygen to the roots. Some growers will even replant a heavily overwatered plant, to get some oxygen immediately to the roots.

Why is my whole plant wilting, curling, with tips turning black and leaves turning yellow? Question: Why is my whole plant wilting, curling, with tips turning black and leaves turning yellow?