Why is my outdoor cannabis plant flowering too early?

Occasionally outdoor cannabis growers experience problems if plants go into bloom far earlier than they should. Without the vital climatic support of warm weather and intense sunlight, early bloom is unwelcome and confusing for the grower, often resulting in small plants and poor yields. There are a few reasons why this could happen. The good news is that the solutions are easy to implement.

When does cannabis start flowering outdoors?

Normally, cannabis starts to flower in response to the changing seasons and the impending arrival of autumn/fall. This is an evolutionary safeguard to ensure that the plant has time to produce and ripen the cannabis seeds. This ensures the next generation of plants for the following season.

Outdoor photoperiod cannabis plants

Photoperiod feminised cannabis strains tend to enter bloom as they sense the day length shortening. Short daylight hours are an indication that the autumn/fall is approaching, the plants respond with hormonal changes triggering bloom.

Outdoor autoflower cannabis plants

Autoflower strains initiate bloom at a point dictated by their genetic composition. This is usually around a month after autoflower seed germination, but on slower flowering autoflowers it can take up to 2 months. The grower isn't able to initiate autoflower bloom by trying to artificially manipulate the grow environment or light hours. Instead the plants flower ‘automatically’ at a time of their own choosing.

Outdoor regular cannabis plants

When planting regular cannabis seeds for outdoor growth the onset of bloom is the same as that when using photoperiod feminised cannabis seeds. Long hours of darkness, or a sense of decreasing day length, is sufficient to initiate bloom in regular cannabis strains.

Pro tip: How to detect early flowering signs for cannabis? Look for signs of pre-flowers where the branches meet the main stem. These give an early indication whether the plant will be male or female. Female plants show a calyx which may have a couple of hairs (pistils) growing out. Male plants, which may show their sex sooner than female plants at the same stage of development, produce small ball-like growths that look similar to miniature grapes.

Key reasons why outdoor plants flower too early

Even the best outdoor grows can have unexpected issues, such as early flowering. Usually the reason is simple to find.

Starting your plant too early

If you get your outdoor plants going early in the season, e.g. around March the dark overnight period is still long enough to force photoperiod feminised strains to bloom.

This can be an issue for the growers that were tempted outdoors a little too early in the season (perhaps due to a freak early heat wave). The best option is to ensure that you have a period of artificial light to break the period of overnight darkness.

A security light, or similar, which comes on for just a few minutes will do the job and ensure the plant remains in vegetive growth. With prolonged vegetive growth the plant can grow into a large size, especially if it was started early in the year.

In Europe many that grow at Southern Latitudes (Spain, Italy, Greece etc) will start their outdoor plants as early as February, perhaps with protection from a heated greenhouse/polytunnel (if local conditions are still a little too cold). Using artificial lights on for a small part of the overnight ensures the plants grow in veg mode even though the days have perhaps only 9 hours of light.

Outdoor growers that put their plants out in e.g. May often never see their outdoor plants flower too early. That’s because the number of daylight hours in May is significantly higher than March, making it easy for photoperiod feminised cannabis strains to settle into veg mode with the long summer days.

Dark period exposure

Even though it may be warm enough to grow cannabis outdoors there may be insufficient light to allow vegetive growth. It’s one of the challenges for those growing in countries where the hot weather arrives slightly before the longer days.

It can also be a challenge for those with heated greenhouses/polytunnels who are keen to start their outdoor cannabis seeds as early as possible. Some strains can have slightly differing responses to the length of the day. One strain may grow in veg mode under a given day length, whereas a different strain may respond with early flowering.

Abrupt light cycle switch

The stress of a sudden change in light cycle can also shock a cannabis plant into early bloom. This could happen, for example, if a plant grown on a 24-hour indoor grow cycle was placed outdoors.

The sudden change in the amount of light hours can be stressful to the plant which may respond by flowering - even if outdoor light hours are more than 12 and the plant might normally be expected to grow in veg mode.

Again, the problem is easily solved by giving the plant extra artificial light during the evening. Perhaps by bringing the plant into a lit garage at night or arranging a security light to occasionally come on and light up the area where the plant resides.

Pro tip: Some cannabis seed genetics are known to flower early. ‘Fast’ photoperiod feminised seeds (e.g. Think Fast) contain recessive (i.e. non-dominant) autoflower genetics, meaning you may be able to harvest a month earlier than usual. For outdoor growers with unstable late-season weather, ‘fast’ photoperiod strains along with autoflowers may be the best options.

Pros and cons of early cannabis flowering outdoors

Many people traditionally associate early flowering outdoor cannabis as a problem. A sign that the plant will be small, with lower yields than expected. But to some growers early flowering, if properly controlled, can be used to great advantage.

Pros

•    Early flowering outdoor cannabis strains is a term often used to describe traditional outdoor photoperiod strains that finish earlier than usual. These can be very useful strains, especially if your late-season weather can be bad. ‘Fast’ photoperiod strains with recessive autoflower genetics such as Dutch Passion’s Think Fast finish in September in the northern hemisphere, that’s around a month earlier than many traditional outdoor strains. Perfect if you can't guarantee the autumn/fall weather.

•    Those that enjoy growing multiple successive outdoor autoflower harvests find it is a convenient, and fast, way to spread the risk. With 2 or 3 successive autoflower harvests each year, it’s not a disaster if one of those crops fail.

Cons

•    Those that want to start their photoperiod feminised seeds in February will find that the long nights may force their plants into early bloom far too early in the season, resulting in poor growth and results.

Can you reverse an early flowering cannabis plant?

Thankfully you can! But prevention is better than cure. Take time to look at your grow situation and identify any possible causes. Would it help if you could improve the transition process when moving an indoor plant outdoors - perhaps adjusting light hours gradually? Are you trying to plant out too early in the year when the nights are simply too long? Is a particular strain repeatedly going into early bloom when the others are behaving themselves?

When to re-veg an early flowering plant outdoors?

If early flowering issues are something that you have seen before then it makes sense to initially grow your preferred outdoor cannabis seeds in containers, rather than rooting them directly into the ground. With your plant in a container, it is easier to move it to an area that receives additional artificial light to break the long night hours.

Those with indoor grow rooms can simply bring the plant to an indoor grow room. Autoflower plants can't be reverted to vegetative growth, but cannabis plants grown from feminised seeds can be re-vegged. Just put them under 18-24 hours of light.

Those growing in a greenhouse or a patio/back garden may find some security lighting that comes on during the evening (even if only for 30min or so) will be able to break the bloom cycle. You will get heavier yields from an outdoor plant that was restored to veg growth after a premature (and undesired) flirtation with bloom. Some growers report that sativa strains may be easier to re-veg than indicas.

When not to re-veg an early flowering plant outdoors?

If your plants have only gone into bloom a month earlier than expected (as opposed to 2-3 months) you may wish to simply leave it to continue bloom rather than attempt a re-veg. The early finish may even be beneficial if you occasionally struggle with poor weather around the normal bloom time.

Pro tip: Make sure you can finish up by the end of the outdoor season. Being realistic, rather than excessively optimistic, about the length of your grow season is a key quality of the experienced outdoor cannabis grower. A few checks online will show you the likely dates of the first late-season frosts & general weather concerns.

If you do have doubts about your ability to finish photoperiod feminised strains in time, then autoflower seeds are the best alternative. Northern European growers in general, and UK growers in particular, can suffer especially difficult outdoor grow conditions. The following guide to growing cannabis outdoors in the UK contains numerous proven tips and advice for those growing in variable climates.

Give love to your cannabis seeds and you’ll get it back

Many of the challenges of outdoor growing can be avoided if the grower is able to buy proven outdoor cannabis seeds. Not only should you have solid, reliable genetics which will behave and  grow/bloom predictably. But you should also benefit from professional breeding techniques & natural selection which will ensure in-built genetic resistance to some of the common diseases.

Most importantly of all, professionally bred outdoor cannabis seeds will have what it takes to cope with variable weather and cool/grey conditions.

An outdoor grow will often be around a 5-6 month process, so it makes sense to invest time in research before you buy cannabis seeds. If you need some extra inspiration from those that have already grown Dutch Passion outdoor seeds then please check out the hundreds of grow reviews in the Dutch Passion blog site where you will find all the grow archives.