There is not a lot of info on when to top because all plants take their time. I think the general rule is top in veg. Most top 1-3 times as long as you remember to add 3-10 extra days in between for healing.
WHEN TO TOP CANNABIS?
There are two schools of thought concerning the appropriate time to top cannabis plants. Old school growers are generally inclined to be more patient. While Millennials prefer to top right away. Waiting a month or more before commencing pruning is far too long for some.
Topping infant cannabis plants very early sets them on track to become bushes. Expect an extended vegetative growth cycle too. Waiting until plants get to the 4th week of vegetative growth before topping is less stressful. Although, not always practical with taller rapid growing strains.
As a rule of thumb, topping is always performed during vegetative growth. Save some exceptional circumstances. Also, most growers allow 1-2 weeks recovery time before repeating the process to further enhance cola development.
Tips for Topping & FIMing
Here are some extra tips to ensure topping and FIMing your marijuana plants goes perfectly every time!
Don’t Top or FIM Too Early!
With both topping and FIMing, you remove some of the growth on the end of a cola of a young marijuana plant, which causes the plant to stop focusing on one cola (like a Christmas tree) and instead to create many bud-laden colas (grow bushier).
If you Top or FIM the plant too early, it will have a hard time recovering. It may seem like a good idea, but you will get the best results and fastest recover if you wait until the plant has enough nodes.
Wait Until Plant Has at Least 3-5 Nodes (FIMing) or 4-6 Nodes (Topping)- Topping or Fimming a Too-Young Seedling Will Dramatically Slow Down Growth. If You Wait Until Plant is Growing New Leaves Every Day, Recovery Will Be Much Faster.
Growers use the plant’s natural response to FIMing/topping to produce short bushy plants with many colas. After the plant has been switched to the flowering stage, the wide spread of colas allows the plant to efficiently use indoor grow lights to produce the biggest yields possible.
If you choose to use either of these methods, you will get the best results by doing it when the plant is young, usually when it has around 3-6 total nodes formed. Generally, you would only want to FIM a plant that has just 3 nodes, and wait until 4 nodes to top the plant.
These young cannabis plants are almost ready to be topped or FIMed. Cannabis plants can be FIMed before they can be topped.
You get great results by breaking the tendency of the plant to grow one main cola while the plant is still short, because you can arrange your multiple colas however you want as the plant develops, instead of dealing with a Christmas tree shaped plant.
You can also top or FIM your plant later in the vegetative stage, but you will have a longer main stalk, giving you less ability to arrange the colas the way you want.
After being topped or FIMed, your plant will need some time spent recovering in the vegetative stage, though generally this just causes the plant to ‘fill out’ more instead of growing taller, which is often desirable for indoor growers.
This plant was trained for ~2 dozen colas in the vegetative stage
Important: Don’t Top or FIM in the Flowering Stage; It’s Too Late!
Topping and FIMing techniques should only be used in the vegetative stage! In fact, any training technique that involves cutting or damaging your plant should optimally be done in the vegetative stage of cannabis growth, before the flowering/budding stage begins.
In the flowering stage, only gentle training techniques such as LST or other types of bending should ever be used to change the shape of the plant.
A plant with many colas can only be achieved by training a plant from early in the vegetative stage
Cannabis plants are much less tough in the flowering stage, and they no longer are growing vegetatively (producing new stems or colas) by the time they hit about week 6.
If you watch a plant in the flowering stage, you’ll see that it doesn’t get taller or develop growth nodes after about week 6. It only “focuses” on making buds. Topping or FIMing at this point won’t do any good. Damaging your plant during the budding stage will often cause a reduction in your final yields because you’re just taking away more plant/bud sites and may cause unnecessary stress during the crucial bud-building phase.