Indoor Growing: How to Switch to Flowering
When growing indoors, the transition from the vegetative phase to flowering is one of the most important moments of the entire cultivation cycle. A number of factors determine when the right time is, and correctly timing the switch will largely affect the quantity and quality of the harvest. We will guide you through the most important aspects of the transition to the flowering phase and suggest some advanced growing techniques that can help you achieve a better yield.
What is the difference between the vegetative phase and flowering?
To begin, let’s clarify what we mean when we talk about switching from the vegetative to the flowering phase. Plants go through four stages in their life: first they germinate, then they become seedlings, next comes the vegetative (growth) phase, and finally flowering. While in the early stages plants focus on producing new leaves and roots to capture more light and nutrients, during flowering they start forming buds that mature into flowers, fruits, and seeds.
How do plants know when to start flowering? Just as they rely on light for photosynthesis, they also use sunlight to signal changes in the seasons. For short-day plants, the earlier the sun sets, the faster they transition to flowering; for long-day plants it’s the opposite. This phenomenon is called photoperiodism, and we cover it in more detail in one of our previous articles on our blog.
Outdoors, plants usually need little help, but with indoor growing the day/night cycle is in the grower’s hands. The grower decides whether the light regime keeps plants in the vegetative stage or if it’s time to flower. Critical day and night lengths vary between species, but for most short-day plants (which include many popular indoor crops, including medicinal and aromatic herbs) the trigger to switch to flowering is a shortening of the day to around 12 hours (the 12/12 regime). During the vegetative phase most growers maintain a light schedule of 16–18 hours light and 6–8 hours dark.
What to watch for when switching to flowering
Although indoor growers can control many factors, the timing of switching lights often also depends on things we cannot fully influence. Plant height and shape, the condition of the root system, and any training techniques already applied all play a role.
Plant height and shape
Many novice growers underestimate how much plants will stretch after switching to flowering. Some species and varieties can stretch up to three times their height during the first weeks of flowering. Always keep in mind how much space plants have above them. During the vegetative phase growers use pruning and other techniques to shape plants so that after switching they fill the grow area and as many tops or flowers as possible are exposed to light.
Root system
Besides vertical growth and leaf production, plants spend much of the vegetative phase developing the root system. The amount of space for roots varies with the cultivation method, but whether you grow in hydroponics or in pots, you should not rush root development. Once a plant begins to flower, it directs most of its energy to bud formation and needs all the nutrients the roots can uptake. If you switch to flowering too early, you will reduce your end-of-cycle yield. There’s no exact science for timing, but most plants need at least three weeks after being placed in their final location before they are ready to start flowering.
Advanced growing techniques
To maximize yields many growers use various innovative techniques that influence plant growth and development. It should be noted that not all techniques are suitable for every species or variety, and their use is left to the reader’s discretion.
Sea of Green (SOG)
The Sea of Green (SOG) method involves growing many small, short plants crowded together. The goal is for plants to start flowering as soon as possible without forming many side branches. Growers using this technique typically switch to flowering when plants are 15–30 cm tall. The result should be many plants with a single main top.
Screen of Green (ScrOG)
Although it shares a similar acronym with the previous method, the Screen of Green technique is essentially the opposite. ScrOG involves placing a support net about 30–60 centimeters above the plant base and weaving the tops through it so the canopy becomes as evenly spread as possible. With patience and experience this method can fill the entire grow area with a single plant or just a few plants.
Lollipopping
The popular pruning method called “lollipopping” involves removing all branches except the largest ones that promise the biggest yield. Proponents argue that lower, shaded buds often won’t mature, so it’s not worth the plant’s energy and nutrients to support them. Before you start pruning, make sure plants are healthy and sufficiently developed so you don’t hinder their growth.
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