For those who live outside moderate climate zones, such as in northerly and southerly regions of the globe or in locations near the equator, growing outdoors can be a bit tricky. If you grow in northern climates, nature may not give your plants enough time to complete flowering by the time the winter cold sets in. A similar problem can be if you grow near the equator. There, your plants can go through a very long period of vegetative growth, convincing you to initiate force-flowering to prevent them from growing out of control. Below, we provide an overview on how to force cannabis flowering outdoors.

force cannabis outdoors


For cultivators who grow cannabis in the northern regions of Europe (or those in the Southern hemisphere respectively), force-flowering outdoor plants is a way to make sure that crops can finish before the cold winter weather arrives. In these zones, flowering will start as the daylight hours become shorter, but the winter frost will be arriving just a few weeks afterwards, potentially destroying your crop and your harvest. When you start flowering early, however, you can plan your grow accordingly and give your buds the extra days they need to fully ripen.

While force-flowering can be a necessity in these aforementioned climate zones, it is also a way for growers in other climates to cultivate multiple harvests in one single season. By strategically planning a crop and then force-flowering at a particular time, some growers can harvest as many as 2 or 3 cycles per year. This means that outdoor cannabis growers can start planting very early in spring and then flower a part of their crops for a harvest in June, with the rest of their plants being ready by autumn.

Seasoned cultivars can plan their forced flowering in such a way that they can harvest every 2 or so weeks in what is called “perpetual harvests” all year long.


Some locations and climate zones allow you to essentially grow cannabis at any point throughout the year. Cultivars that happen to grow in these warm-temperate regions, like in parts of Southern Europe or the tropics, may start to force-flower at any time. There may be local conditions, however, that should be taken into account; but otherwise, there won’t be any restrictions on when to flower.

This is different in cool-temperate climate zones like in the UK or some Northern parts of Europe. There, autumn can be cold and damp, correlating to a full, natural flowering cycle lasting through mid-October. Rather than waiting for the natural flowering period to set in, a grower may force-flower their crops prematurely, say in July, to ensure that they can harvest early enough. Here too, local conditions can play a role in when it is best to force-flower. Last but not least, the time to force can also depend on the particular strains being used and their unique flowering durations.

As an example, let us take an outdoor grow in the UK. Flowering there will usually not start before September. To avoid the strong winds and rainy conditions in autumn, it can be a good idea to start flowering as early as mid-June or early July. Growers in these climate zones will normally start their plants indoors since these zones that have a cold and/or wet autumn will also have a spring that will be too cold for starting plants outdoors.

cannabis plant outdoors flowering tent


The basic principle behind force-flowering cannabis outdoors is that you artificially reduce your plant’s natural daylight hours to provide them with longer hours of uninterrupted darkness each day. You do this by covering up your plants with some type of material that doesn’t allow any light through. In the simplest case, you could use a tarp of some kind; in a “fancier” case, it could be that your plants are sequestered inside some type of enclosure, possibly even with an automated roof on a timer.

Urban cannabis growers that have only a small number of plants outdoors, like on their balcony or in their yard, could make a simple frame from wood and some light-proof material. They can then put this frame over their plants in the evening to ensure that plants get the required 12 hours of darkness for flowering. Folks who are not too keen on DIY can also look into toy tents, which they can re-purpose as a plant cover as long as the fabric used is light-proof.

What also works is a light-proof garden shed. In this instance, you would move your plants into the shed at night. Obviously, this means that your plants would need to be in containers and that you, depending on the number of your plants, would have to lug them in and out of the shed on a daily basis. Likewise, if you grow in a greenhouse, all that you’d need there would be light proof curtains if you want to initiate flowering.

cannabis outdoor flowering forced tent ventilation


When you cover your plants or put them away somewhere to start flowering, heat is likely to become an issue. Together with your light-proof tent, shed or DIY light-blocking frame, you will want to maximise good air circulation so that your plants won’t die from the heat. There are some elaborate solutions to provide your plants with adequate temperatures, but in some cases, a simple fan with a cool breeze can be all that’s required.

When you decide to go the route of force-flowering your outdoor crop, it is very important to stick to the schedule and not miss one single day. Cannabis that has started flowering is very sensitive to any type of changes in light exposure; some forgetfulness could easily make your plants revert back into the vegging phase, something which would seriously hurt your harvest. Seasoned growers who might depend on force-flowering because of their climate zone may want to consider some kind of automated system.

Likewise, any type of cover or enclosure for your plant needs to be 100% light proof. Sometimes, street lights alone can make flowering impossible. No light should reach your plants in the hours of darkness.

What if you grow indoors, but your plants won’t go into flowering? If you’re one of the many cannabis cultivators who grow under artificial light and your plants just won’t bud, check out our blog on “What To Do When Your Homegrown Cannabis Won’t Flower.” This article will help you get your indoor plants flowering in no time.

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