Can you top autoflower plants i.e. remove the growing tip in order to produce a bushier and shorter result? It’s a good question and one often asked by expert auto growers looking to push their autoflowering cannabis seed genetics to the limit. Topping autoflowers is a complicated topic.
In simple terms, autoflowers can indeed be topped but it is not often recommended. Many autoflower growers have never topped a plant and would be cautious about ever doing so. For good reasons too.
Whether topping an auto makes sense for you depends on your grow situation, your goals, the strains you’re growing and your attitude to risk. Read on to understand more.
Can you top autoflowers and is it recommended?
When you top a cannabis plant you remove the growing tip. This is known as high stress training, ‘HST’. The words ‘high stress’ are important since any auto is working against the clock with a fixed life cycle.
Any stressful event, including the high stress technique of removing the growth tip of a plant, takes a week or perhaps more for the plant to recover.
For plants grown from photoperiod feminised cannabis seeds this time is less important than it is to an auto. That’s because a photoperiod feminised plant can be grown almost indefinitely under vegetative growth conditions. You can top the plant once, or repeatedly, and allow as much time as you wish for the plant to recover and grow.
Plants grown from autoflower seeds can be topped, but the high stress training technique will cost your autoflower several days to recover from the process. When you only have 75 days or so in total, the cost of topping an autoflower could be a smaller final plant. Autoflowers can be topped but few people routinely recommended the practice. Indeed, it is probably only a minority of autoflower growers who regularly top their plants.
So who would top their autoflower plants and what would they be hoping to achieve by doing so?
How does topping affect autoflowering cannabis?
Topping autoflowers results in bushier plants that are not as tall as they would otherwise have been, but with plenty of side blooms. This is exactly the same result that you would get by topping plants grown from photo dependent feminised cannabis seeds. The disadvantage of topping autoflower plants is that the time required for the plant to recover may outweigh the benefits intended by the topping process. That’s probably the main reason that more people don’t risk topping autoflower plants.
What would a grower hope to achieve by topping autoflower cannabis strains?
Cannabis grows with apical dominance, meaning the central stem/bloom grows taller than the rest of the plant. That’s due to growth-inhibiting plant hormones (called auxins) that travel from the growing tip down the stem and keep the nearest branches short. When the growing tip is cut off, so is the supply of auxins.
This allows branches immediately below the removed growing tip to grow with increased speed and vigour. The main central bloom is replaced by a fast growing, bushy canopy of side blooms.
For growers with restricted vertical space, topping is a good way to control vertical growth. This is especially relevant when growing e.g. stretchy and problematically tall sativa strains.
Topping is a high stress technique which can deliver good results especially when growing photo dependent feminised strains. Plants can be topped several times over a long vegetative growth period (e.g. 8-12 weeks) to produce a bushy plant with multiple heavy yielding blooms.
The result can be seriously heavy yields. But autoflowers often simply lack a sufficiently long life cycle to be able to take full advantage of yield increases that may be presented by topping.
What are the best autoflower strains for topping?
The best autoflower strains for topping tend to be those with the longer average grow cycles. These strains often have sativa leaning phenotypes that may take 12 weeks, or perhaps longer, to complete their life cycle.
The extra couple of weeks beyond the average 75 day auto life cycle can allow the auto plants the chance to recover from topping and deliver a good harvest.
Conversely, those autoflower strains with the faster life cycles would have the least available time to accommodate recovery from topping. Such fast flowering autoflowers would be least recommended for topping.
That said, the following auto strains can take from 12-15 weeks of indoor growth under 20 hours of daily light to grow from autoflower seed to harvest. Although Dutch Passion don’t routinely recommend the toping of autoflower plants, the following strains would be the ones that might be better able to deal with the process.
Auto Ultimate cannabis seeds
With a typical seed to harvest time of 12-15 weeks, Auto Ultimate is a true XXL yielder that can fill a grow room on her own in optimised conditions. These exceptional best-selling autoflower seeds are part of the Dutch Passion Classic cannabis seed collection, home to some of the best ever Dutch Passion strains!
Auto Glueberry OG cannabis seeds
Auto Glueberry OG is a cannabis cup winning autoflower seed variety that can take 12 weeks or more to grow from seed to harvest. This makes her better equipped to deal with the stress of topping than some autos. Watch out for the insane resin levels and outrageous XL yields!
Auto Lemon Kix cannabis seeds
Auto Lemon Kix can take around 12 weeks to grow from autoflower seed to harvest. Part of the USA Special cannabis seed collection – expect heavy yields and loud flavours! Best of all Auto Lemon Kix is part is the Dutch Passion Extremely High THC seed category. This is home to the most potent 10-15 of Dutch Passion’s strains.
When is the best time to top autoflowers?
One of the difficulties is knowing when is the perfect moment to top autoflowers. Typically, growers would not want to remove the growing tip until 3-5 nodes have already formed.
That could take around a month of growth after germination. If the growing tip is removed too soon, the immature plant and root system is shocked and subsequent growth is permanently stunted.
If the growing tip is removed too late the autoflower plant could already be in early bloom and subsequent plant development could be adversely disrupted. Not too many people routinely top their autoflowers, but those that do tend to do so after/around 4 weeks of growth.
One of the dangers of topping autoflower plants is that the grower misses out on the main central bloom. This can often account for around 20% of the total harvest.
So any grower considering topping their autoflower plants needs to understand the genuine risks involved. That’s one of the main reasons that few people recommend topping autoflowers.
When growing autoflowers in a SOG-style grow topping is never recommended either, since in a SOG grow the main bloom often accounts for a large part of harvest.
Topping autoflowers gone wrong (mistakes to avoid)
Topping an autoflower is a higher risk growth strategy which the majority of growers tend to avoid. However, if you do want to try topping an autoflower plant, here are a couple of tips:
- Always use clean blades. A sharp razor is ideal, so are a sharp pair of horticultural scissors. If you use a blunt blade and create a rough cut you are adding further risk to an already high stress process.
- Avoid topping an autoflower if it is known for having a fast life cycle. Strains such as Auto Blueberry and Auto Blackberry Kush should be avoided since these can be ready to harvest just 8-9 weeks after seed germination. With such short life cycles and lack of recovery time, these autos are not at all suited to being topped.
- Rather than throw away the growth tip of the plant after topping, you may wish to try planting it (maybe with a dip of hormone rooting powder on the cut) and see if you can get a few buds from it eventually.
How to maximise autoflower yield?
If you are serious about maximising your autoflower yield then there are some other tips and techniques that may be much less risky than topping your autoflower plant.
If you’re determined to get heavy harvests from your auto crops then it helps to start with the heaviest yielding autoflower seeds. Here’s our seed recommendations as well as some useful tips to get the best from them.
Many average hobby growers step up their yields by making upgrades to their lighting. In simple terms, more watts means heavier yields. But there’s more to it than that. You need to ensure temperatures remain under control, ventilation is good and spectrum/intensity is optimised. LED is more expensive than HPS lighting, but is strongly preferred by quality conscious growers seeking the highest value harvest.
Cannabis roots love growing in a well-aerated grow medium in a fabric smart pot (or air pot). With ample root space you will typically see heavier harvests than those you could get from a plant grown in a smaller container. If you grow your autoflower seeds in 5 litre containers then you may find heavier yield improvements come when you upgrade to a 25 litre air pot or felt sack.
Grow room environment
Avoid large temperature swings, extremes of humidity, under feeding, over feeding, over-watering, under-watering etc. Avoiding these will reduce plant stress and help optimised growth. Likewise, ensuring your garden remains free of pests and disease all helps your plants to remain in top health which ultimately helps optimise yield.
Many growers get great results when using concentrated nutrients. But some growers, especially less experienced growers, can struggle with plant nutrition.
Over feeding and over watering are the two most common errors seen by less experienced growers. These mistakes cost auto plants valuable time to recover from, time which they don’t really have.
One easy way to keep your autoflower plants in the nutrient sweet spot (without over feeding or under feeding) is organic slow release nutrients, meaning you just add water for much of the grow. Bio Tabs nutrients are particularly recommended.
Scrog or LST
Because autoflower plants grow within the boundaries of a fixed, pre-determined life cycle many growers avoid topping and prefer low stress techniques (LST) or SCROG to try to maximise yields.
One of the fastest ways of growing the largest autoflower plants is to consider a hydroponic grow technique such as hydroponics. Deep water culture is a particularly good method for maximising harvests
Hydroponic cannabis grow guide
Autoflowering cannabis seeds, it’s also about quality as well as quantity
Remember, it’s not just about maximising yield. There’s little point maximising the yield of poor quality cannabis genetics, you should be growing the best genetics. Always buy the best quality cannabis seeds you can get.
The price difference between a premium quality autoflower seed and a cheap one is just a couple of Euro’s, Pounds or Dollars. That’s a small amount of cash in relation to the value of your final crop.
Even the best professional growers can’t produce a high THC crop from low THC genetics. So buy the best autoflower seeds you can get from a cannabis seed company with a reputation you can trust.
Dutch Passion are widely recognised as one of the best in the business when to comes to autoflower seeds. You can choose from a wide selection of high THC seeds, cannabis cup winning seeds and even the worlds highest THC autoflower seed!