The nutrient requirements will change dramatically when the plants enter the flowering stage, and this may be a little hard for new growers. You can feed your plants 1-2 times every week, gradually increasing the nutrients, but at the same time pay attention to your plants' reactions after each feeding.
Unlike the vegetative stage, when the flowering process begins, the plant needs less nitrogen. Feeding the plants properly during the flowering phase will result in the healthy development of the plant together with an abundant harvest, which is what every grower wants.
Generally, you want to water every 2 or 3 days during Flowering and you want to water enough that 10-20% of water comes out from the pot as runoff. You can check your soil moisture by sticking a finger in the pot: if the soil is dry a couple inches down, then it is time to water again.
For soil growers, plants can be fed once every second or third watering. If plants are fed with every watering then nutrient buildup and lockup becomes a problem causing stunted growth, “crows foot” (curling downwards of the leaves), leaf burn, deficiency symptoms, burnt and damaged root system and decreased yields.
In these final weeks, phosphorus, potassium, and calcium are still your most important nutrients. Two weeks before harvest, however, you'll want to flush your plants with plain, pH-balanced water. This encourages them to take up all remaining nutrients, and helps preserve the natural flavour of your buds.
The bigger the leaf area, the bigger your buds will be. Nitrogen is the nutrient needed most for this green growth. When plants reach their mature size and begin flowering, they need more phosphorus, the nutrient most essential for budding.
During flowering, switch the lighting schedule to 12 hours on and 12 hours off. The key for maximum yields is to provide large amounts of light and to distribute it as evenly as possible across the canopy. Space your lights accordingly.
Flowering – 5-20-5 or 5-25-10 – During flowering, you want to prioritize phosphorous to promote bud growth and make sure to limit nitrogen so your plant doesn't get too tall or “leggy.” You want it to concentrate on developing huge buds, not lots of stems or leaves, and phosphorus will make your buds grow.
An overabundance of nutrients—primarily nitrogen and phosphorus—in water starts a process called eutrophication. Algae feed on the nutrients, growing, spreading, and turning the water green. Algae blooms can smell bad, block sunlight, and even release toxins in some cases.
Generally, flushing cannabis normally takes place two weeks before it is harvested. If the plant has an 8-week flowering period, flushing should start 6-weeks after the beginning of the flowering stage when trichomes begin to form a cloudy white color.
Stunted growth
The new branches that grow during this crisis are mainly stunted and weak. Overwatering cannabis plants during the flowering stage is detrimental to yields because it minimizes the development of bud sites.
Plants don't need daily watering. Instead, water deeply but less frequently. Deep waterings allow the water to seep beneath the roots, which encourages the roots to grow downward.
Excess water reduces oxygen in the soil, which damages fine roots and renders the plant unable to take up water. Plants exposed to excess moisture show the same symptoms as plants under drought stress. The primary symptom of excess moisture is wilting or yellowing of lower and inner leaves.
In week 5 of flowering, you can observe the buds all over your plant becoming thicker. You may also spot new buds growing in new places such as along the main cola. With buds abounding, your cannabis plants will get fatter every day. This is a surefire sign you are in full flowering mode.
To help plants get into the flowering stage, the amount of light hours must be reduced to less than 12. In these light hours the plant creates sugars through photosynthesis. During the dark hours, these sugars are used to create buds. The appearance of buds is one of the clearest signs of flowering.
In weeks 6-8, the buds of your plants will begin to harden; the delicate trichome heads of your flowers will cloud and turn amber, and the once milky pistils of your buds will shrink, turn brown and become fragile. Also, as your plants continue to ripen, new aromas, flavors, and pigmentation will develop.
Too much nitrogen and phosphorus in the water causes algae to grow faster than ecosystems can handle. Significant increases in algae harm water quality, food resources and habitats, and decrease the oxygen that fish and other aquatic life need to survive.
“If you don't get enough water, hard stools and constipation could be common side effects, along with abdominal pain and cramps.” Dull skin. Dehydration shows up on your face in the form of dry, ashy skin that seems less radiant, plump and elastic.
If overhydration worsens, confusion, seizures, or coma may develop. When overhydration occurs and blood volume is normal, the excess water usually moves into the cells, and tissue swelling (edema) does not occur. When excess blood volume occurs, fluid can accumulate in the lungs and lower legs.
Increasing the amount of CO₂ in your grow room can help you grow bigger, denser buds. By doing so, you'll help plants photosynthesise faster and encourage them to take up more nutrients and water.
The last three weeks is when your buds can actually gain the most weight – that is if you feed them Overdrive®. After your peak bloom phase, your plants enter their late bloom phase (the precise timing and length of which depends on the strain of cannabis you're growing).
Lack of light is perhaps the most common reason that cannabis produces fluffy, light buds. You may have noticed the lower, puny 'popcorn' bud sites that form below the main canopy. Often these buds are discarded by growers allowing the plant to focus biochemical energy on the main blooms.
To stimulate blooming, choose fertilizers with a higher percentage of phosphorus compared to the percentage of nitrogen and potassium. Healthy flowers start with vigorous root systems, and a potassium boost can ensure your flowers get a good start.
Topping to increase the number of colas
Prune to clear off dead leaves to help your plants focus their energy on the live parts of the plant. Prune large leaves which get in the way of light reaching the colas. Topping is a form of pruning and involves pruning off the branch tip of the main cola.
FEWER HOURS OF LIGHT PER DAY. You can significantly speed-up the growing cycle of a photoperiod strain by exposing it to around 10–11 hours of light each day. Reduced light exposure will trick your plants into thinking autumn is just around the corner.