25 Simple Ways to Protect and Preserve Cannabis Flower During Cultivation and Harvest

With cannabis, starting strong in the field or grow room gives you a better chance of ending up with a truly stellar crop. But what does that mean? To us, that means protecting your plant from harmful invaders such as pests, disease, and even an overabundance of nutrients. 

Protect Cannabis Plants

1. Bud Rot (Botrytis)

A gray mold that occurs in environments with poor air circulation and high moisture, bud rot is a common fungus across the plant world. Bud rot—or botrytis—causes poor water and nutrient absorption, eventually resulting in plant death. At the onset, the plant’s stem will appear mushy and gray, and as bud rot progresses, the fan leaves will wilt, turning yellow and burnt.

Prevention comes down to controlling humidity and airflow. In a grow room, you must constantly circulate clean air and install a dehumidifier to remove excess moisture from the air. Also, space the plants apart so air can move freely between them, and inspect your crop daily for standing water. 

2. Powdery Mildew

Another common intruder in cannabis crops is powdery mildew. This mold slows the growth of cannabis plants, causing them to shrivel and die if left untreated. Symptoms of powdery mildew include a loss of color on the overall plant and bright green or yellow spots on the leaves. Basically, it sucks the energy from the plant.

Unlike other types of mold, powdery mildew spores don’t need standing water to germinate. Instead, this scourge only requires brief periods of high humidity to spread.

Molds can wreak havoc on human workers, too. Some could potentially present a health threat when inhaled, particularly among immunocompromised individuals. For example, molds produce mycotoxins, like Aspergillus, which can significantly impact vulnerable people with a lung disease known as allergic bronchopulmonary aspergillosis.

These nasty mycotoxins are hardy even beyond the grave, as dead pathogens can continue to trigger allergies and asthma after they’ve been killed with treatment. That’s why when it comes to powdery mildew and other molds, it’s all about prevention. 

To prevent powdery mildew, avoid wild fluctuations in temperature and use HVAC and dehumidification systems to stabilize the environment. When powdery mildew is spotted, it’s crucial to cut those leaves immediately. However, workers often inadvertently spread spores while attempting to salvage the plant. For heavy infestations, it might make more sense to scrap the crop rather than risk your entire operation. 

3. Pests 

There’s no shortage of pests in the plant world, and cannabis is just as susceptible as anything else that grows in dirt. Some of the creepy crawlies and airborne irritants that endanger cannabis crops include:

• Aphids
• Broad mites
• Caterpillars
• Inchworms
• Crickets
• Fungus gnats
• Grasshoppers
• Leaf miners
• Mealybugs
• Russet mites
• Slugs and snails
• Spider mites
• Stink bugs
• Thrips
• Whiteflies

Each pest causes different types of damage to plants. For example, russet mites cause curling on leaf edges and brittle, dull-colored leaves and stems. Caterpillars, on the other hand, just munch holes in your fan leaves. If left unchecked, pests can cause irreparable damage. 

It’s incredibly important to inspect your plants on a daily basis when it comes to any infestation. They say, “an ounce of prevention is worth a pound of cure,” but harmful pesticides have no place in a cannabis grow effort. If any sort of infestation crops up, treat it organically. Natural pest repellants include:

• Neem oil
• Diatomaceous earth
• Homemade foliar sprays
• Companion planting
• Pheromone traps
• Ultrasonic soundwaves 
• Predator introduction

4. Nutrient Overload

Also known as nutrient burn, overfeeding cannabis is just as deadly as underfeeding. Excessively feeding plants can cause undue stress, and you’ll see this stress in yellowing leaves that ultimately turn brown and die. 

Traditional fertilizers can give your plants the nutrients they need to thrive, but overfeeding can turn even the most well-intentioned cultivator into the root of the problem. It’s especially easy to overload crops with nitrogen. As such, chart a course for low and slow feeding. Adhere to your fertilizer’s instructions and keep a daily log of feeding times and amounts.

Preserve Indoor Grow

Even in a controlled environment, such as an indoor grow room, things can go wrong. In fact, crops that are planted and cared for indoors occasionally require even more attention than those grown under the sun.

5. Quarantine Clones 

Whenever you introduce a new plant into your grow room, you run the risk of introducing new diseases and pests. Newly acquired clones can include horticultural hitchhikers, which will infect your entire garden if given the chance. 

Quarantining agricultural products and plants is standard practice in commercial agriculture; in some cases, it’s enforced by the U.S. Department of Agriculture. To quarantine a cannabis clone, place it in isolation in a separate location for four weeks, while constantly observing, inspecting, and testing the plant.

6. Grow Room Cleanliness (Including Equipment) 

Just like any car, computer, or home, a grow room requires routine maintenance in order to function properly. That means keeping the space absolutely pristine and ensuring all of your equipment is as clean as possible. 

Keeping a tidy grow room and sanitized equipment helps prevent pests, diseases, and mold. A daily cleaning regimen shared by the grow team, good airflow and filters, and even insect traps can help to fortify the growing space.

Make sure you have these supplies on hand at all time:

• Sponges and cloths
• Gloves and protective goggles
• Cleaning agents (detergent, hydrogen peroxide, vinegar, etc.)
• Alcohol wipes 
• Distilled water 
• Duct tape
• Broom and dustpan
• Mop and bucket
• Germ-killing sticky mats
• Cleanroom shoe and boot covers

Next, regularly clean these specific areas and pieces of equipment:

• Tabletop caster units
• Vertical grow racks
• Floor
• Carbon filters
• Grow system
• Ventilation system
• Irrigation system
• Grow lights

You can also employ negative air pressure to keep any possible contamination from escaping the cleanroom.

7. Humidity Control 

In the plant world, humidity is crucial to evaporation and transpiration. These two important parts of photosynthesis make up the very process in which plants convert light energy into chemical energy—an essential ingredient to growth.

When humidity levels are too high or too low, you run the risk of stunted growth or outbreaks of powdery mildew, bud rot, or nutrient deficiencies. Depending on the stage of growth, optimal humidity levels vary. 

• Seedling stage: Humidity should be set around 70 percent.
• Vegetative stage: Humidity should be set between 40 and 60 percent.
• Flowering stage: Humidity should be set between 40 and 50 percent. 
• Late flowering stage: Humidity should be set around 40 percent.

The best ways to control humidity in the grow room include:

• Using a humidifier or dehumidifier
• Improving ventilation 
• Keeping soil surface moist
• Optimizing drainage
• Sealing and insulating the grow room
• Defoliating

8. Airflow (Sterilized and Filtered) 

It wouldn’t be a stretch to say that most cannabis pests and diseases can be traced back to a poorly ventilated grow room. Maintaining proper ventilation—and ensuring that air is sterilized and filtered—is fundamental for any healthy grow room. But aside from pathogens and pests, your plants need fresh air to fuel photosynthesis and “breathe.” 

One surefire way to have sterilized and filtered air is through the use of high-efficiency particulate air (HEPA) filters. HEPA filters—the standard across multiple industries—remove particles by forcing air through a fine screen. With 99 percent efficacy, HEPA filters can be used in both vacuum and air purification systems.

To take the airflow purifying mission to the next technological level, check out the Air Sniper, which uses four zones of Ultraviolet (UV-C) light, multiplied using Photocatalytic Oxidation (PCO) elements. This tool destroys airborne viruses, bacteria, and molds, preventing their proliferation before harming your plants or personnel.

9. Light Cycles 

Let there be light! More to the point, let there be sufficient light! Understanding the light cycle and spectrum needs of your cannabis plants can lead to better yields and healthier plants with robust cannabinoids and trichomes. 

First, know that there are four distinct stages of cannabis growth: germination, seedling, vegetative, and flowering. Next, understand that each growth stage has a different light cycle requirement in terms of how much light they need and what spectrum of light you should use. 

• Germination: Red light for 16 hours a day.
• Seedling: LED blue light for 18 hours a day.
• Vegetative: Full-spectrum light for 18 hours a day.
• Flowering: Full-spectrum light for 12 hours a day.

10. Fungicides 

There are millions upon millions of fungi species around the world, and while your cannabis plants might not be under constant threat of all of them, the ones that could make it into your grow room can cause serious harm. Microscopic fungal spores travel in the air, floating through the grow room and landing on plants. Once on the plant, spores can lead to various types of mold, bud rot, and other diseases. 

Utilizing fungicides early on is key to winning the battle against fungi. Conventional fungicides are an immediate, if non-organic, option. These chemicals effectively kill fungi on cannabis plants, but harsh chemicals aren’t ideal in an enclosed grow room.

Organic fungicides are far more appealing to cannabis consumers, who are notoriously selective when it comes to choosing a marijuana source. Potassium bicarbonate is a natural fungicide that can reduce the spread of powdery mildew. Hydrogen peroxide also has antifungal properties. 

Other Fungal Remediation Methods

Beyond fungicides, there are a handful of interesting methods for remediating an outbreak of fungi in the grow room. If a state testing agency detects a fungus in your operation, you can perform these remediation efforts and then have the state return for a retest. These remediation methods include:

• Dry Heat
• Gamma Radiation
• Gas Treatment
• Radio Frequency
• UV Light
• Steam Treatment
• Reactive Oxygen

11. pH Levels 

pH (potential hydrogen) measures the acidity and alkalinity of your soil medium and controls how well your plant absorbs nutrients. Dialing in the correct pH levels takes skill and precision, but the importance of hitting the right levels makes learning such skills all but mandatory in cannabis cultivation. 

Cannabis plants tend to prefer a slightly acidic environment for its roots, as such pH levels help avoid nutrient lockout. 

• For growers using soil, pH levels should be adjusted to a range of 6 to 6.8
• Growers utilizing a soilless garden should set the pH range between 5.5 and 6.5

Different nutrients are absorbed at different pH levels, so allowing a varied range such as what’s listed above helps plants absorb a variety of nutrients.

Preserve Outdoor Grow 

For cultivators who have ample outdoor space for a cannabis grow, there are specific ways to protect and preserve the crop. From harnessing the power of the sun and keeping an 

eye on the weather to scheduling harvest, trimming, and curing, grows in the great outdoors deserve a closer look.

12. Spacing Plants 

Cannabis plants require plenty of room to stretch their stems and branches. But more than that, overlapping plants can spark competition in your garden, causing plants to siphon energy from one another, which will make at least half of your crop weaker than the rest. 

To guard against this and ensure your entire crop reaches its potential, space your plants at least three to five feet apart. Doing so sets you up for success, as every inch of each plant will get adequate airflow and the right amount of sun. 

13. Weather Preparedness 

Even with radar, satellites, and other tech from the National Weather Service, storms can strike suddenly. Weather will always be somewhat unpredictable, so protecting your outdoor grow from the ravages of the elements should be a high priority for any cultivation team. To keep your plants safe:

• Know your local climate: Growing high-quality outdoor marijuana requires an intimate knowledge of your local climate and seasons. Understand seasonal temperatures, how much rain your area gets, how low the temperature plummets, and the amount of daily sunshine your crop will receive. 
• Know your strains: Some cannabis genetics adapt to specific climates, growing more easily in certain weather conditions. Pay close attention to strains, or cultivars, if you want a successful harvest. 
• Know your temperature: Cannabis is known for its heat tolerance, but extreme fluctuations in temperature could prove detrimental to plants. Cannabis loves daytime temperatures between 75 and 85 degrees Fahrenheit, but temps above 88 degrees or below 60 degrees could delay growth. 
• Know your harvest schedule: If you live in an area with a cold and rainy season, carefully schedule your planting so that cannabis is harvested before bad weather rolls in. Plan your cultivation so the rainy season makes the end of the flowering stage and the start of harvest time. 
• Know your plants: If your plants do get caught in the rain, lend a helping hand. Immediately after rain, gently shake excess water off of the leaves and the stems; lingering moisture can lead to an outbreak of mold.

14. Remove Leaves for Airflow 

Cannabis fan leaves absorb light, turning sunshine into energy the plant needs to grow. Leaves also have pores that open and close (stomata), which allows the plant to “breath.”

Fan leaves contain trace amounts of THC and CBD, and while some cultivators use fan leaves to make hash and various types of concentrates, cultivators growing cannabis for dried flower should be far more concerned with the precious buds. 

Removing or pruning fan leaves is an essential step when cultivating cannabis. When fan leaves grow too large or too abundant, they could block the sunlight and the airflow to certain parts of the plant. This can hinder the production of cannabinoids and trichomes.

Removing fan leaves:

• Improves light penetration
• Improves airflow
• Helps prevent mold and pests
• Redirects energy to buds

Generally speaking, you want to remove some fan leaves during the vegetative stage, when your plants reach around 10 inches in height.

15. Fungicides 

Since cannabis plants are all susceptible to certain kinds of fungi, you want to be as diligent in protecting your outdoor cannabis plants from fungi as you would be with an indoor grow. 

Fungal spores are constantly flying around, looking for a dark humid place to land and proliferate. Unfortunately, grow sites offer the ideal circumstances, as there is plenty of warmth and moisture. 

Here are some common cannabis fungi:

• Gray botrytis
• Oídio
• Mildew
• Tizne or bold
• Fusarium
• Root rot
• Verticulosis
• Sclorotinia

Some of these fungi are more destructive than others. To prevent an outbreak, make sure there’s plenty of space between your plants for airflow. Also, thoroughly check your plants for signs of fungal infection on a daily basis. If a fungus does appear, use a safe, organic fungicide to save your crop. 

16. pH Levels 

As it is with indoor grows, outdoor cannabis prefers soil that’s slightly more acidic. Keep your soil pH in a range of 6 to 6.8. This ensures your plants absorb the nutrients they need to grow strong and healthy. You can take the guesswork out of pH levels by purchasing a pH test kit. You can also follow time-honored home gardening tips to conduct a pH test without any sort of professional kit.