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 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 feminized cannabis strains tend to enter bloom as they sense the day length shortening. Short daylight hours are an indication that fall is approaching, and 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 in slower-flowering autoflowers it can take up to 2 months. The grower isn’t able to initiate autoflower bloom by artificially manipulating 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 outdoors, the onset of bloom is the same as when using photoperiod feminized cannabis seeds. Long hours of darkness, or a sense of decreasing day length, are 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 feminized strains to bloom.
This can be an issue for growers 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 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 vegetative growth. With prolonged vegetative growth, the plant can grow quite large, especially if it was started early in the year.
In Europe, many growers in southern latitudes (Spain, Italy, Greece, etc.) start their outdoor plants as early as February, often with protection from a heated greenhouse or tunnel if local conditions are still a little too cold. The same can apply in parts of the southern United States, where growers may also be tempted to start early during a warm spell. In both cases, using artificial lights for a short part of the night ensures the plants stay in veg mode even though the days may have only 9 hours of light.
Outdoor growers that put their plants out in, for example, 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 feminized 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 vegetative growth. This is one of the challenges for those growing in regions where the hot weather arrives slightly before the longer days. That includes parts of southern Europe and the southern United States.
It can also be a challenge for those with heated greenhouses or tunnels who are keen to start their outdoor cannabis seeds as early as possible. Some strains can have slightly different responses to day length. One strain may stay in veg mode under a given day length, while another 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 number 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 stay 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 feminized seeds (e.g., Think Fast) contain recessive (non-dominant) autoflower genetics, meaning you may be able to harvest a month earlier than usual. For outdoor growers with unstable late-season weather—whether in Northern Europe or northern U.S. states—fast photoperiod strains along with autoflowers may be the best options.
Pros and cons of early cannabis flowering outdoors
Many people traditionally see early flowering outdoor cannabis as a problem—a sign that the plant will be small with lower yields. 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, around a month earlier than many traditional outdoor strains. Perfect if you can’t guarantee the fall weather.
• Those that enjoy growing multiple successive outdoor autoflower harvests find it 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 fails.
Cons
• Those that want to start their photoperiod feminized 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 possible causes. Would it help to 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 while others are behaving normally?
When to re-veg an early flowering plant outdoors
If early flowering issues are something you’ve seen before, it makes sense to initially grow your preferred outdoor cannabis seeds in containers rather than rooting them directly in the ground. With your plant in a container, it’s 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 indoors. Autoflower plants can’t be reverted to vegetative growth, but cannabis plants grown from feminized seeds can be re-vegged. Just put them under 18–24 hours of light.
Those growing in a greenhouse or a patio/backyard may find that security lighting that comes on during the evening (even for just 30 minutes or so) can break the bloom cycle. You’ll get heavier yields from an outdoor plant 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 prefer to simply let them continue blooming 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 overly optimistic, about the length of your grow season is a key quality of the experienced outdoor cannabis grower. A quick check online will show you the likely dates of the first late-season frosts and general weather concerns.
If you have doubts about your ability to finish photoperiod feminized strains in time, then autoflower seeds are the best alternative.
Growers in northern climates—such as Northern Europe, Canada, or the northern United States—often face especially difficult outdoor conditions. For more details, check out our guide to growing cannabis outdoors in the UK. While written for the UK, the tips apply broadly to growers in any variable climate.
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 starts with proven outdoor cannabis seeds. Not only should you have solid, reliable genetics that grow and bloom predictably, but you’ll also benefit from professional breeding techniques and natural selection that build in resistance to common diseases.
Most importantly, professionally bred outdoor cannabis seeds will have what it takes to cope with variable weather and cool, gray conditions.
An outdoor grow will often take around 5–6 months, so it makes sense to invest time in research before you buy cannabis seeds. If you need inspiration from those who have already grown Dutch Passion outdoor seeds, check out the hundreds of grow reviews in the Dutch Passion blog archives.