how to induce flowering outdoors

Force-Flowering Cannabis Outdoors: Yes, You Can Do It!

Growing cannabis outdoors can be tricky because you must rely on the natural light cycle to support your plants’ growth. But the location of your garden or the local climate might not always allow your plants to go through their entire flowering cycle as intended. That’s where force-flowering can help you achieve a perfect harvest! Here’s how.

Learn how to force-flower your outdoor weed plants.


Outdoors, under the sun is arguably one of the best ways to grow your own weed. Unfortunately, growing outdoors can be tricky if you live far north or south or along the equator. Luckily, you can overcome some of the challenges of growing in these areas by force-flowering your outdoor plants. In this article, we’ll walk you through the process, so you can gain more control over your outdoor grow.

When Does Cannabis Flower Outdoors?

Photoperiod cannabis plants start to flower at the end of summer (following the summer solstice), once the days get shorter and the nights grow longer. Latitude obviously has a big impact on when weed flowers, as it correlates to the number of daylight hours in a particular region.

In general, however, cannabis plants will start flowering after the June solstice (June 20th or 21st, depending on the year) in the Northern Hemisphere and after the December solstice (December 20th or 21st) in the Southern Hemisphere. Keep in mind that the switch to bloom is a lot more gradual outdoors, as daylight hours decrease by a matter of minutes every day.

How Long Does the Flowering Stage Last?

How long a plant takes to flower outdoors varies depending on its genetics and its environment. In general, however, cannabis plants can be harvest-ready between September and November in the Northern Hemisphere and March–May in the Southern Hemisphere.

Why Would You Want to Force-Flower Cannabis?

When we think of outdoor growing, we tend to believe we have almost no control over the light cycle of our cannabis. But that doesn’t have to be the case. While there’s a certain beauty to letting nature run its course, sometimes a bit of human intervention can make the difference between an average harvest and a great one.

Benefits of Force-Flowering Outdoor Cannabis Plants

Here’s why you might want to consider forcing your outdoor plants to flower:

Avoid Frost

Areas far north or south of the equator tend to have long, harsh winters that set in a lot earlier than in other areas of the globe. If you’re growing outdoors in northern Europe or southern Argentina, for example, you may want to force your plants to flower a little early to avoid early winter frosts or rain destroying your harvest.

Limit Size

If you live along the equator, on the other hand, you may want to force-flower your outdoor plants to keep them from growing too large. Due to the long, consistent hours of sunlight these areas get all throughout the year, photoperiod strains growing close to the equator can take a long time to start flowering and, given enough space, can grow massive.

Perpetual Harvests

You don’t need to be living in Tierra del Fuego or Oslo to be intrigued by the idea of force-flowering your outdoor plants. In fact, a lot of outdoor growers opt to force their plants into bloom to produce multiple harvests throughout the year. Some experienced growers even produce perpetual harvests approximately every two weeks throughout the growing season.

When Can You Force-Flower Cannabis Outdoors?

If you live in a cool, temperate climate zone (like the UK, northern Europe, or far south in South America), you may face cold, damp autumns and early winters that overlap with the end of your plants’ bloom phase. To stop these conditions from jeopardising the quality and size of your harvest, we recommend forcing your outdoor plants to flower prematurely during mid-June or early July in the Northern Hemisphere and mid-January or early February in the Southern Hemisphere.

In the UK, for example, outdoor cannabis plants naturally won’t start flowering until September (approximately). In order to avoid the harsh rains and winds of autumn, we recommend outdoor growers in the UK force their plants into bloom as early as mid-June or early July. Given the cold spring in the region, you’ll likely also want to start your plants off indoors.

If you live close to the equator or in the tropics, on the other hand, you may be able to grow outdoors all year round. Given these conditions, you can essentially force your plants to flower whenever you like (local weather permitting, of course).

How to Force Cannabis Flowering Outdoors

The principle behind force-flowering outdoor plants is simple; just reduce the amount of light your plants get. How you choose to do this, however, depends on the number of plants you’re growing and the weather in your area.

If you’re growing a handful of plants on a balcony or terrace and don’t have extreme temperatures and harsh rains to worry about, a simple wooden or PVC frame fitted with a light-proof tarp might be all you need; simply pop your plants under the tarp at night and give them a full 12 hours of uninterrupted darkness to force them into bloom.

Alternatively, you could also move your plants into a garage, cellar, or shed at night; just remember that the area needs to be 100% light-proof for the plants to start flowering properly.

If you’re growing a lot of plants, you probably don’t want to lug them around every day. In this case, you may want to consider an automated tarp or roof above them. You can then use a timer to ensure your plants go undercover at the same time every day, without having to move them inside individually.

If the weather in your area isn’t so favourable during early autumn, you may want to invest in a small indoor grow tent complete with a light and fan. Once you’re happy with how your plants have vegged outdoors, bring them into the tent to finish them off without having to worry about the cold, rain, or wind.

Force-Flowering: Factors to Consider When Covering Your Plants

While force-flowering is pretty simple, there are a couple of things you’ll want to keep in mind to make sure the process goes down smoothly.

Air Circulation

When you move your plants undercover, one of the first things you’ll want to think about is air circulation. Stale, stagnant air can drive up the temperature and relative humidity around your plants, creating a breeding ground for pests, fungi, and bacterial pathogens. Whether you’re keeping them under a DIY frame with a tarp or in an indoor grow tent, make sure you have clean, fresh air circulating around the space to keep your plants healthy.


Next, you’ll want to stick to a tight schedule. Photoperiod strains are very sensitive to light cycle changes, and a small slip-up when you’re trying to force them to flower can revert them back to veg or trigger hermaphroditism. For the best results, create a consistent flowering schedule with plenty of reminders to ensure your plants go under and come out of cover at the same times every day.


Finally, you’ll want to make sure that the structure housing your plants during their bloom phase is 100% light-proof. Light leaks during the flowering cycle can cause your plants a lot of stress and interrupt their flowering cycle. Wherever you’re keeping your plants, make sure there is absolutely no light exposure during the dark hours.

Don’t Want to Force-Flower? Try Fast-Flowering or Auto Strains

Rather than having to force-flower your outdoor plants every season, we recommend looking into strains with flowering times suited to your local climate.

Our fast-flowering strains, for example, are specially bred to flower in as little as 40 days. Our experienced breeders have developed these strains especially for growers looking to get to harvest sooner or pump out multiple harvests per season.

Alternatively, autoflowering strains are another great option, especially if you live in the tropics or close to the equator. Unlike feminized or regular strains, our autoflowering cannabis varieties are specially bred with ruderalis genetics and flower automatically based on their age, rather than changes in their light cycle. If you’re looking to pump out multiple harvests per year, our autos are the way to go.

Below are some of our favourite fast-flowering and autoflowering strains:

Candy Kush Express

A cross between Sweet Special and Royal Kush, Candy Kush Express is a well-balanced hybrid with great potency and delicious sweet citrus aromas. A direct descendant of an Afghan Kush, Candy Kush Express boasts a big, heavy stone that’ll leave you glued to the couch for hours. Finally, with a flowering time of only 7–9 weeks, few photo-feminized strains are this quick to reach harvest.

Wondering if it's possible to force outdoor weed plants into flower? Well, it is! Click here to learn everything about force-flowering outdoor cannabis plants.

Outdoor tutorial: force-flowering

Growing outdoors can be tricky in terms of timing, and if you get it wrong–or if your location simply does not allow you the leisure of letting nature take its course–then your harvest may be drastically reduced, if not non-existent. Here, we provide a few helpful tips on how to ensure you get that harvest, wherever you are.

Why should you force-flower cannabis?

Force-flowering cannabis is one simple way to ensure that your outdoor or greenhouse crop begins to flower with enough time to complete its growth cycle before the winter cold sets in and sunlight becomes weak and limited in duration.

In the northern, cold-temperate zones of the northern hemisphere (and the corresponding southern zones in the southern hemisphere), the time between hours of daylight dropping low enough for flowering to begin and winter frost setting in can be insufficient for flowering to complete; thus, artificially reducing hours of daylight prematurely can supply the extra short days needed to achieve harvest.

Force-flowering can also be useful for growers in more favourable climates who wish to produce multiple crops per year (a “perpetual harvest”). Some growers are able to harvest two or more crops per year by strategically depriving plants of light. For example, plants can be started in February or March; some can be harvested by June using light-deprivation techniques, while others can be left to flower naturally in late summer and be ready to harvest by mid to late autumn.

For truly perpetual harvests, a few plants can be induced to flower every week or two (once they have undergone sufficient vegetative growth) so that harvests are similarly staggered.

When to force-flower cannabis?

Your window of opportunity when attempting to force-flower cannabis outdoors depends greatly on your location. In warm-temperate and tropical regions, there may only be a very short period each year in which cannabis cannot be grown, so ensuring that flower cycles end before that cold or wet season sets in is the only real requirement.

In cool-temperate climates such as the UK and the Netherlands, autumn conditions usually become too cold and damp to sustain healthy flower growth by late September to mid-October (although there are reports of outdoor crops flourishing until late November or even early December in some areas, as seasonal climate patterns shift and winters become milder).

Thus, to ensure that your crop finishes in time, it is advisable to commence light-deprivation in mid to late July, depending on the flowering time of the strain.

Naturally, your plants may not begin to flower until September, which can be a wet and windy month in many parts of the UK. In some cases, it may be advisable to commence force-flowering in mid-June or early July, which should provide your plants with enough time to grow vegetatively and complete flowering too.

Starting plants indoors is always advisable, particularly in regions that experience cool springtime temperatures.

Force-flowering cannabis is one simple way to ensure that your outdoor or greenhouse crop begins to flower with enough time to complete its growth cycle