Marijuana plants need more than just sufficient light, water, and carbon dioxide to grow and thrive. They also need plenty of nutrients applied in the right mixtures and at the right times according to their growth stages. This article will focus on one specific aspect of getting your plants the nutrients they need: understanding and developing appropriate feeding schedules for cannabis plants grown in soil.
What Is a Feeding Schedule?
Whether you decide to grow your plants outside in a dedicated cannabis garden, or you want to start an indoor soil-based grow, you’ll need to keep track of everything you feed your plants throughout their growing cycles. Feeding schedules make it easy to ensure that every plant in the garden or grow room has the nutrients it needs based on its size, strain, and growth stage.
Most novice growers start by using the feed charts provided by their nutrient vendors. These feed charts contain all kinds of relevant information about what type of nutrients each plant food contains, how much of each product you should use, and what pH level you should maintain depending on the plants’ growth stage.
How to Read Feed Charts
Feed charts are usually divided into three sections based on the crop’s growth stage. The first section will cover the nutritional needs of seedlings and applies to all plants that have already been germinated but are less than three weeks old. The second applies to plants in the vegetative stage, which lasts around a month for most strains.
The third section of the feed chart is usually the longest. It refers to the nutritional requirements of cannabis plants that are already in flower. You should only switch over to this final section of the feed chart after your plants have begun to produce buds, regardless of how long they were in veg.
Each section of the feed chart should contain at least three columns that refer to the type of nutrients your plants will need, the dilution rate for the plant food, and the ideal pH for your soil. Many plant food manufacturers also include more detailed information about dilution rates, such as the amount of nutrient solution you’ll need to add per liter vs. per gallon of water to achieve an ideal balance.
You may also find information about the ideal PPM and EC for your nutrient solutions. They refer to the amount of total dissolved solids (TDS) in your liquid plant food and its electrical conductivity, respectively. The reason plant food manufacturers include this information in their feed charts is that the concentration of minerals in your soil directly affects the plants’ ability to uptake nutrients.
Keep in mind that the EC and TDS measurements listed on your feed chart refer to the concentration of nutrients in the liquid. They will change when you apply the liquid plant food to your soil. Soil electrical conductivity is influenced by everything from irrigation and evaporation rates to the plants’ nutrient uptake, and more. If you want to keep an eye on your soil EC and TDS levels, you can send samples to a lab or purchase TDS and EC meters for in-house testing.
How to Make the Most of Feed Charts
While feed charts provide a great starting point for beginners, more experienced growers know that they’ll need to make adjustments to their feeding schedules depending on the growing environment and what strains they’ve chosen. When you buy new cannabis seeds for a soil-based grow, you shoulddo some research to see what types of experience other people have had with altering nutrient levels. You should also plan to keep a daily plant journal to keep track of details for each strain, such as:
- When you feed the plants
- What nutrient mix you used
- The dilution ratio you chose
- How your plants are responding to the nutrients
Every day, check your plants for signs of curling or yellowing. Whether you’re growing CBD-heavy strains or kind bud, you’ll want to catch any potential problems with nutrient deficiencies or toxicities early and make adjustments to your feeding schedule as needed. Writing down not just the changes you’ve made to your plants’ feeding schedule but also how they respond is the key to getting everything just right next year.
Ensuring Proper Nutrient Availability
Adding micronutrients and minerals to your soil is the best way to give your plants what they need to thrive. Feeding in soil-based grows can be somewhat of a balancing act, though. If you give your plants too few nutrients, they’ll be stunted and won’t produce prolific buds, but if you feed them too much it can cause nutrient burns.
Nutrient Deficiencies
Depending on their growth stages, marijuana plants require different levels of all the key macro- and micronutrients. Your plant food should contain, at a minimum:
- Nitrogen
- Phosphorus
- Potassium
- Calcium
- Magnesium
- Sulfur
Many specialized cannabis nutrient solution manufacturers also add key micronutrients like zinc, iron, manganese, chlorine, cobalt, molybdenum, and others. The exact nutrient mix will depend on the brand and what stage of growth the plant food targets.
To give just one example, marijuana plants in the vegetative stage need more nitrogen to facilitate leaf and stem growth, while those in the flowering stage use more phosphorus and potassium. If you’re not interested in learning everything there is to know about ideal nutrient ratios for each growth stage, just make sure you’re buying your plant food from a reputable supplier that specializes in cannabis growing products. The company should offer different mixes optimized for each growth stage.
Even if you follow the feed chart provided by your supplier carefully, you could still wind up dealing with nutrient deficiencies if your soil pH is off or you’ve chosen exceptionally hungry strains. Keep an eye out for signs of nutrient deficiencies such as leaf discoloration or curling, brown spots, unusual growth patterns, stunted growth, and reduced bud sites in the flowering stage.
More often than not, nutrient deficiencies can be adequately addressed by slowing increasing the amount of food you give your plants. However, if your plants are only deficient in one kind of nutrient, you may want to switch to a different blend. You can also try foliar feeding your plants to address severe deficiencies quickly before they destroy your crops.
Nutrient Toxicity
Nutrient toxicity, also referred to as nutrient burn or “nute burn,” occurs when growers over-fertilize or overfeed their plants. Though nutrient toxicity can affect the entire plant, from root tips to buds, you’ll likely notice its effects on the plants’ leaves first. The early warning signs of nute burn include extreme deep green leaf coloration, bending at the leaves’ tips, and a slight yellowing at the tips of the leaves.
In its later stages, nutrient toxicity looks more like nutrient deficiency and things can get a little complicated. The plants’ leaves will turn yellow or brown, curl under, twist up, and may die back. If you keep a detailed plant journal, you should be able to catch the nute burn before it gets to this stage.
The best way to address nutrient burn is to flush your soil, then check the EC until it has reached proper levels. You’ll also want to remove any damaged plant tissues and adjust your feeding schedule accordingly to avoid future toxicity problems.
Nutrient Lockout
It’s relevant to note here that the ratio of nutrients in a plant food can impact nutrient uptake and subsequent plant growth. Lockout occurs when plants are oversaturated with certain nutrients, causing the soil’s EC levels to rise to unacceptable levels. Plants experiencing nutrient lockout tend to be weak and stunted and they may develop yellowing or curling leaves.
The problem is, the symptoms of nutrient lockout look an awful lot like those associated with nutrient deficiencies. To determine which problem you have, you’ll want to check your soil’s pH and EC levels and keep careful track of symptoms. Once you’ve determined that nutrient lockout, and not a deficiency, is to blame for your plants’ poor health, you can flush the excess nutrients from the soil and start over using more diluted plant food.
When and How to Switch Nutrient Formulas
You’ll want to switch to different nutrient formulas each time your plants enter a new growth stage. Plan to switch from seedling to vegetative stage plant food at around three weeks into the season when your plants begin producing larger fan leaves.
Most cannabis plants only spend three weeks as seedlings, but the amount of time different strains spend in the vegetative stage is far more variable and can range from 3 to 16 weeks. If you’re growing indoors, switch over to a flowering stage feeding regimen when you change your plants’ lighting schedule. Otherwise, look for the small white pistils, or stigmas, that develop near plants’ nodes as they approach the flowering stage.
Don’t Underestimate the Importance of Proper Feeding Schedules
iguring out what, when, and how to feed your plants is one of the most important aspects of growing cannabis successfully. It’s perfectly fine to start learning the basics by following the exact guidelines on your nutrient solution supplier’s feed chart, but you should plan to make adjustments from there based on your plants’ strains and growing conditions.
Keep an eye out for signs of nutrient deficiencies, burns, and lockouts, and note down every change so that you can avoid making the same mistakes in the future. Once you’ve sorted out how your favorite strains respond to changes in nutrient levels, you’ll be well on your way to optimizing your yields.
