Switching from Veg to Bloom
Plants need at least 13 hours of light each day to stay in veg – a few ‘long’ nights may be enough to trigger budding. Plants begin budding when they get at least 12 hours of ‘uninterrupted’ darkness each night (12/12). This must continue until harvest. Even if darkness is interrupted briefly, flowering will be hindered. In fact plants may revert back to veg unless 12 hour nights are maintained. Employ a timer to help ensure consistency. NOTE: For outdoor grows, light deprivation techniques will need to be employed to trigger flowering when nights are too short.
When to switch? There are 2 main considerations:
• Age of plant: “Cuttings” can be switched as soon as desired, however, for optimum yields it is generally best to wait until the clone has a strong root system (typically 2-3 weeks old). For “seedlings”, if space (and time) permit, better yields can be obtained from a 6-8 week veg period. Alternatively they can be switched straight after germination, however they are biologically incapable of budding until about 3 weeks of age.
• Height of plant: Depending on the strain, plants will generally double in size during flowering. So, if ‘room’ height is limited, the switch to 12/12 will need to be done no later than when the plant has reached 50% of the ‘available’ height (remember to consider the minimum gap distance between lamp and foliage). Topping and LST (see section) are very useful techniques for keeping plants short and bushy and will help enable a long veg (6-8 weeks) if required.
Bloom Phase (Powering the Flower)
As a rule-of-thumb, in the first 2-3 weeks of flowering the plant will continue to grow in height (termed “flowering-stretch”) and buds will begin to form. Following this, floral growth will dominate and veg growth will slow then stop. Some general principles:
1. Lights are switched “off” for 12 hours per day – uninterrupted! Use high pressure sodium (HPS) lamps, rich in the yellow-red parts of the lighting spectrum.
2. Increase the air-exchange rate. Flowering plants tend to prefer a gradual lowering of relative humidity to around 40–60% (high humidity can cause rot and mildew). General optimum temperature is 68-82 deg F (20-27 deg C). Also, carbon dioxide consumption is reaching its peak and is therefore often the weakest link (Fig 7.1.).
3. Avoid lamp burn by ensuring to keep foliage at a safe distance (Table 3). Do not keep plants too far away though as this will encourage “stretching”.
4. Avoid stressing plants by pruning during flowering unless there is over-crowding or damaged growth. Major ‘structural’ pruning should be conducted during veg.
5. Don’t get complacent with bugs or diseases such as powdery mildew! Regularly check both sides of foliage on all your plants—especially those that sometimes get overlooked in the corner.
Avoiding the Stretch!
Many growers complain that their plants ‘stretch’ excessively, especially in the first 2-3 weeks of flower. Along with potentially reduced yields, lower foliage will be more difficult to light efficiently, and top foliage is at risk of being burnt if lamps cannot be raised any higher. Plants can also be gangly and weak and therefore susceptible to breaking once loaded with buds. Although “flowering-stretch” is biologically unavoidable, there are ways of minimizing it:
1. Source a strain which is prone to being short.
2. Ensure plants receive enough light. Lack of light causes an additional “stretch” response whereby plants grow taller and with fewer buds. Lack of light can be caused by:
• Shading, due to plants being positioned too close to one another. It is generally more productive to plant fewer plants, rather than more.
• Lamps being too far from foliage will cause plants to ‘stretch’ to find light. Note, avoid having lamps too close as this will also induce stretching.
3. Use an MH lamp for the first 2-3 weeks of flower, then switch to HPS. The orange/red spectrum of HPS and other “flowering-specific” lamps encourages stretching. Conversely, the “blue” spectrum of MH tends to inhibit stem stretch.
4. Keep the night (lights-off) temperature cooler but within about 9 deg F (5 deg C) of the day temperature. Ensure the day temperature is kept below about 82 deg F (27 deg C).
5. Maintain sufficient air flow. This tends to promote shorter, stronger plants.
6. Topping and LST are ideal for modifying the plant to ensure all foliage receives enough light. The majority of this should be done during veg.
© Andrew M Taylor (FloraMax)
FAQs
Growers can switch to the flowering stage as soon as the clone has established a solid root system. In optimal conditions, plants should be kept in their vegetative stage for approximately 60 days. This time period should give the plant the opportunity to maximise yield and acclimatise to growing conditions.
When can I switch to flower after topping? ›
This stress is only heightened for a plant that goes through topping. However, the light shift and the beginning of flowering is one of the most stressful times for any plant. Considering this, the majority of growers will tell you to wait 1–2 weeks between the end of topping and the beginning of flowering.
How do you enter the flowering stage? ›
When you grow indoors, flowering will begin once you switch your lights to 10-12 hours of darkness. For most cannabis strains, the flowering period will last about 7-9 weeks, although some sativas require even longer for their buds to mature.
What nutrients should I use during flowering stage? ›
Nutrients for Cannabis plants in the flowering stage
The main nutrients that the Cannabis plant needs to develop are Nitrogen (N), Phosphorus (P) and Potassium (K). When the plant starts to bloom, the concentrations of P and K must be increased progressively, while the N concentrations are lowered.
How often do you water flowering stage? ›
Generally, you want to water every 2 or 3 days during Flower 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.
Should I use both veg and bloom switches during bloom? ›
Always have both switches ON (VEG and BLOOM) once you plants are in the Blooming stage. It will cost more in electricity but your final harvest will reward you!
Should I defoliate before switching to flower? ›
We recommend defoliating vegging plants just before you switch them to bloom: Start by removing big, hand-sized fan leaves first. These tend to overshadow almost anything below them, making it hard for light to properly penetrate your plant's canopy.
Can you top plant in flowering stage? ›
Important points for topping:
2. Healthy plants usually take 2-3 days to recover from topping. After topping, do not remove the leaves from that node as these are needed to power growth of the branches from that node. Never top during flowering as it causes too much stress – which slows growth and inhibits yield.
How close to flowering can you top? ›
The side branches will end up filling out a bit more so it won't be a huge loss but all topping should be done during the vegetative stage and preferably not within two weeks or so of the plant starting the flowering stage.
Should you remove fan leaves during flowering? ›
You can remove fan leaves during flowering in much the same way you do during veg. Prune away large leaves that are overshadowing bud sites, as well as dead or dying fan leaves. One thing to keep in mind is that you should prune in intervals, giving at least a couple weeks between each session.
Stop Watering 1-3 Days Before Harvest – After flushing, in the final days of harvest, you can further stress your plants by stopping watering. You want to allow the plant to start to wilt just a small amount, because then the plant “thinks” it is dying and as a last-ditch effort, it will increase resin development.
When should I switch to bloom nutrients indoors? ›
Indoor – When you switch lights to 12 hours of darkness a day the plant will naturally go to a flowering state. A week after the switch is when you should start feeding plants Bloom fertilizer.
What to add to increase flowering? ›
Using potassium helps develop the quality of flowers and fruits already set. To increase the numbers and quality of flowers on a plant, gardeners can increase the availability of these nutrients to their plants by adding fertiliser.
What to add during flowering? ›
Potassium is an essential element for plant growth, and high levels are required during the fruiting and flowering stage. Although potassium isn't physically part of any plant tissue, it activates many key enzymes for plant growth and reproduction.
When should I start flushing my trichomes? ›
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.
Should you water more or less during flowering? ›
Watering during the flowering period
During the pre-flowering and early flowering stage, the plants don't require additional watering. However, once the plants enter the peak flowering stage, the buds start sucking the soil dry. The buds are filled with water; it's logical that more watering is required.
What week Do buds swell the most? ›
Weeks 1-3 – Transition
Also known as the flowering stretch—you'll notice a sudden increase in growth over these three weeks. Your plant needs to be big and strong enough to support the buds that'll be growing over the next few weeks—it can double or even triple in size.
How long should you flower vs veg? ›
The vegetative stage in Cannabis plants may last from 3 to 16 weeks, or even more in outdoor crops. Most growers vegetate their indoor plants for 4-8 weeks, depending on the desired plant size. Cannabis plants are usually able to start flowering from the 4th week of the vegetative stage.
Does cutting blooms encourage more blooms? ›
The practice of deadheading, or removing flowers from a plant as they fade to promote even more flower production, will give you more blooms than you thought possible! This simple technique can be applied to both annuals and perennials to give you a longer blooming season.
Do you give your plants nutrients during flowering? ›
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.
Once between the beginning of Flower and the 3-week mark. 3 weeks after beginning flower is the last time you'll want to defoliate.
How late into flowering can you lollipop? ›
WHEN TO LOLLIPOP CANNABIS. Most growers will agree that week 3 of flowering is the right time to start lollipopping. After a couple of weeks in the bloom phase, most cannabis strains will begin to display multiple bud sites along shoots.
Can you defoliate too much in flower? ›
The inexperienced grower may be tempted to over-defoliate a cannabis plant. This can reduce final yield potential, by stunting growth and removing healthy bloom points. Some growers question the fundamental logic of cannabis defoliation.
How long can you keep a plant in flowering stage? ›
Most growers will move their plants into bloom after about four weeks of vegetative growth, but you can technically keep them in this phase indefinitely.
How many nodes should I have before flowering? ›
It is recommended that you wait until your plants have at least four nodes before topping them, and most growers recommend topping the plant above the sixth node. Nodes are the part of a plant that connects new stem offshoots with older growth, which can form a branch, a leaf, or in the case of cannabis plants, a bud.
How long should plants be in flowering stage? ›
Cannabis plant flowering stage
This is when plants start to develop resinous buds and your hard work will be realized. Most strains flower in 8-9 weeks, but some can take even longer, especially some sativas.
How long after switching to 12 12 will I see buds? ›
When you're ready for plants to start the flowering stage, change your lights to a 12/12 cycle (12 hours with the light on and 12 hours with it off ). You will see signs of flowering in 1-3 weeks. On average plants will be ready to harvest after 8-11 weeks of flowering.
What should my buds look like at 5 weeks? ›
The buds aren't really big, but they're starting to produce a lot of resin. The buds have to get hard and heavy over the next weeks. They won't get much larger in size, but will become heavier and of better quality.
Plants need at least 13 hours of light each day to stay in veg – a few ‘long’ nights may be enough to trigger budding. Plants begin budding when they get at least 12 hours of ‘uninterrupted’ darkness each night (12/12). This must continue until harvest. Even if darkness is interrupted briefly, flowering will be hindered. In fact plants may revert back to veg unless 12 hour nights are maintained. Employ a timer to help ensure consistency. NOTE: For outdoor grows, light deprivation techniques will need to be employed to trigger flowering when nights are too short.
As a rule-of-thumb, in the first 2-3 weeks of flowering the plant will continue to grow in height (termed “flowering-stretch”) and buds will begin to form. Following this, floral growth will dominate and veg growth will slow then stop. Some general principles:
3. Avoid lamp burn by ensuring to keep foliage at a safe distance (Table 3). Do not keep plants too far away though as this will encourage “stretching”.
Many growers complain that their plants ‘stretch’ excessively, especially in the first 2-3 weeks of flower. Along with potentially reduced yields, lower foliage will be more difficult to light efficiently, and top foliage is at risk of being burnt if lamps cannot be raised any higher. Plants can also be gangly and weak and therefore susceptible to breaking once loaded with buds. Although “flowering-stretch” is biologically unavoidable, there are ways of minimizing it:
