Pot Plant Problems

by Maggie McCutcheon

IG: @magininka

Growing marijuana plants can be a challenge, especially if you’re growing outside. In addition to maintaining proper levels of sunlight and water, the outdoors is home to insects and animals who may want a piece of your harvest. Here is a list of some of the more common critters out there who may be drawn to your crops by the alluring fragrance and what you can do about them.

Common Pests:

Spider Mites
You may recognize these little guys if you’ve ever tried to keep a Majesty Palm. They sap the chlorophyll from the leaves, causing them to yellow. They leave white spots which are eggs. To protect their offspring, they weave gummy webs that are particularly hard to get rid of on a pot plant. If the webs get on the flowers, it could contaminate your harvest and waste your product.

They can be treated with a high powered hose (not recommended during flowering) or with neem oil if they are already a problem. You’ll want to repeat the treatment for a bit until you’re certain the mites and eggs are eradicated. However, it’s best to avoid them completely by using sterilized soil and sanitizing your tools, hands, and air supply.

Like mites, these little, yellow, winged bugs consume minerals in your plants causing yellow and wilted leaves. They reproduce incredibly fast, giving live birth as often as a dozen times a day. In addition to eating the plants, their excrement attracts ants causing another infestation issue and they have been known to carry viruses from near-by plants.

Aphids can be treated with a solution of garlic or tomato leaves and mineral oil soaking in water for 12-24 hours. You can also try introducing ladybugs or parasitic wasps to fend off the little guys. There are a variety of species of aphids and specific species of wasps to counter them.

Fungus Gnats
Fungus gnats are little black bugs that crawl and fly around the lower portion of your plants. They love the moist soil and, although they won’t touch leaves and flowers, they can do some damage to the root system and reduce drainage. This will make your plants more vulnerable to further damage and infestation.

A good method of prevention is to keep screens on windows and doors and to keep them shut when possible. It is recommended to put a cloth on the soil around your plants to prevent females from laying eggs and to keep the top layer of soil as dry as possible. You can achieve this from watering from the bottom if your planter allows it. Another solution is to sprinkle your soil with anti-fungal, aromatic cinnamon. Since you probably already have some in the cupboard, it’s a cheap and easy solution to the problem.

Algae is a wonderful breeding place for fungus gnats so use an algaecide in your water if you spot the slimy growth on your growing medium.

These are rarely a concern for indoor plants but, in outdoor plants, can pose a serious threat to your crops. They are tiny, soft-bodied, and ovular in shape. They are coated in a white, powdery wax to protect themselves, and some may have little bumps on their bodies that look almost like legs. They move slowly but, once settled, form clusters. They attack your plant by piercing it and sucking the sap out of stems, leaves, and flowers. Their excretions can cause sooty mold to grow.

Like aphids, you can introduce insects to counter their presence and prevent their spreading by spacing your plants out. Additionally, you can remove parts of the plant that are already damaged and use a mixture of equal parts water and alcohol on a cotton cloth to wipe them away. Neem oil is an effective solution as well.

Thrips are small, fast moving, and are either worm-like in appearance or dark and winged depending on their age. Like mealybugs, they pierce your plant and suck away at all the nutrients, leaving shiny or slimy-looking, silver or bronze spots where the leaves were attacked. The leaves will eventually start dying off if left untreated.

Neem oil effectively fights off thrip infestations as do Spinosad products, which are organic and harmless to pets, children, and plants. Spinosad can be sprayed heavily on leaves and roots with hardly any negative effects. Spinosad can be added to your water to get thrips via the roots.

Cannabis plants are susceptible to many common garden concerns. Different fungi, like Alternaria and Fusarium, can take siege on your crops. You can identify Alternaria by leaf necrosis (dark, dry spots on the leaves), which in serious cases can cause the plant to die. It frequently attacks the stems of seedlings causing spots towards the base of the stem. Fusarium causes rotting at the base of the stem, nutritional deficiencies (leaves turn yellow and necrotic without falling away), root rot, and stems cut open reveal brown vascular bundles.

Alternaria can be stopped by a natural fungicide like Horsetail or Potassium soap applied every 10-15 days. But fungi are hard to identify and treat so prevention is your best bet. For instance, Fusarium has no effective treatment so a strict hygiene regime should be your main concern. Dispose of your affected plants as soon as possible if you suspect Fusarium to avoid its spreading.

Mildew, another fungus, shows itself by leaves drying out, becoming necrotic, and falling away. It can be prevented with a chamomile broth (made from 50g of flowers per liter of water and diluted with 9 liters of water per 1 liter of broth), garlic broth (50g of garlic per liter of water diluted in 4 liters of water per 1 liter of broth), or horsetail. Fungicides are also available. And, as with Fusarium and Alternaria, sterilized soil, trimmers, irrigation, pots, etc. are important but so is removing rotting debris from around your plants and avoiding over-watering.

Root rot is a common gardening concern, and cannabis plants are no exception. Growth slows, leaves wilt, and the plant’s condition rapidly deteriorates. Once it sets in, there is precious little you can do to save your plant so good drainage, air circulation, and appropriate levels of sunlight are important. Always disinfect everything.

Grey mold is an annoying fungus that commonly strikes indoor plants. It appears on buds as blue-green hairs resembling lint. It turns to dark spots and leaves buds feeling slimy. Infected stems turn yellow, and any growth past the infection will wilt. Remove affected buds with sterilized scissors at least an inch below and destroy it outside of your grow room. Wash your hands and sterilize your scissors after removing the grey mold because it spreads very, very easily.

Companion Plants:

Another solution to prevent and eradicate pests and disease is to intersperse your marijuana garden with naturally repellent plants. Your weed plants will love hanging out with some of this cast.

Basil’s strong fragrance keeps away thrips, beetles, aphids, and flies. Some growers report an increase in oil production and flavor as well. As an added bonus, you’ll have tons of basil around to eat.

Another edible, beans also absorb nitrogen from the air and deposit it into the soil as nitrites. It just so happens that marijuana plants love nitrites and, in the company of beans, grow stronger and are protected from nitrogen deficiency (which can be fatal for your poor plants).

Garlic is wonderful for keeping pests and molds away as it’s a natural fungicide. As mentioned above, it can also be used out of the ground in a solution to treat pests like aphids.

More for outdoor growers, marigolds are a great way to distract pests away from your cannabis plants. Many animals attracted to your plants will skip the cannabis and go for the marigold instead. You can even create what is virtually a forcefield by planting marigolds all around your crops.

Another fragrant herb, many pests hate the smell of mint and avoid it entirely. It also does a wonderful job of hiding the fragrance of your crops to preserve your privacy. Mint spreads rapidly and can overrun your garden, so it is recommended to plant it in a pot and keep it near your plants instead of in the ground.

Spicy peppers are formidable at keeping away larger animals for outdoor growers. Deer, mice, and rabbits are all threats but conveniently hate chili peppers. Furthermore, the root system of the peppers emits a chemical that protects your weed plants from rot. This is great if drainage or high precipitation is an issue.