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Guide to Growing Cannabis Outdoors in the UK

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Added 27 May 2022

Growing cannabis outdoors

Cannabis plants are notoriously demanding plants, and they need the right conditions to grow well with resinous buds. If you live in the UK, you might think it's challenging to grow cannabis, given the climatic conditions of your region.

The notion is somewhat true, but growing cannabis is not impossible, even in the UK. On the contrary, growing cannabis is as easy as growing it in Afghanistan with suitable measures and methods.

Think of it this way: you are presented with some challenges if you live in the UK, but if you play your cards right — pick the right strains, time the growth and harvest well, ward off pests, and follow the proper training techniques — you will be rewarded with many heavy buds at the end of the growing season. 

In this article, learn all about growing cannabis in the UK. You'll know everything you need to know, including the right methods, best strains, a rough growing calendar to help you harvest, and the legality, so you're not in the dark. 

Sounds good?

Let's begin. 

Growing Cannabis in the UK

Growing cannabis in the UK

The weather in the UK is unpredictable. Typically, it rains almost throughout the year, but you can also experience rain, sunshine, and heavy winds — all in one day! So while others may enjoy it, growers usually find it hard to plan things. However, you can still turn the situation to your advantage if you follow the right steps. 

That said, rain is good as cannabis is a thirsty plant, and you also get to enjoy a couple of other advantages. For instance, the weather will mostly be dry during the late bloom stage, which is ideal for good bud development. 

And during most months, you know exactly what kind of weather to expect (in most cases), so you can time your growth and harvest accordingly. 

On the flip side, too much rain can also spell disaster for your plant. If you do not take suitable measures, your plant can become prone to bud rot and root rot, affecting your plant's growth and yield.

Lastly, you have to worry about the legality of growing cannabis. Since it is illegal, you'll have to grow your plant discreetly and carefully. More on this later. 

Best Strains for the UK

Strains to grow in the UK

Before growing your plant, you need to pick the right strain. Unfortunately, the wrong strain may lead nowhere as the plant won't be able to withstand UK's weather conditions. 

So, to avoid such problems, you need to pick the right strains. Here are the four most ideal strains for the UK climate.

Northern Light 

Northern Light has terrific genetics. Thus, it can handle UK's humid conditions. And with a flowering time of just 7 to 8 weeks, it can reward you with a yield of around 575 to 625 g/plant. In addition, it has a high THC content of 18%, with a spicy, fruity flavor, offering a potent body high. 

Haze Berry

If you live in the South West, you should pick Haze Berry. The slightly warmer conditions are perfect for this plant as it has a more extended flowering period of 9 to 11 weeks. And you can expect a yield of up to 650 g/plant with berry-flavored buds that offer a stimulating cerebral high.


Northern growers should check out Critical. It is ideal for short growing seasons of the north, and its genetics can handle the occasional cold snaps as well. It has a flowering period of 7 to 9 weeks and can give you a yield of 600 to 650 g/plant. 

And being a descendant of Skunk and Afghani, this strain offers a stimulating head high while relaxing your body. 

Frisian Dew

Frisian Dew is another photoperiod strain that's quite popular in the UK. Due to its sturdy genetics, it can grow up till Northern England and is usually harvest-ready by the first week of October.

Some other strains that you can consider are White Widow Feminized, Jack Herer Auto, Dutch Passion, Holland's Hope, and Durban Poison.

More on the UK Climate

cannabis plants growing in the UK

Most parts of the UK enjoy consistent rain. And that's a good thing as your plant won't experience draught and will always have plenty of water to drink.

Apart from the showers, the UK also has a temperate climate with winters and summers, but there are seldom extreme weather conditions that can damage your plant. 

The climate offers an average of almost 1300-1350 daylight hours. In addition, you may experience approximately 130-140 days of rain per year, which is a good balance for ideal plant growth.

You can divide the climate into four climate segments according to the regions to make things easier.

South East

Thanks to the continental winds, the South East UK experiences cold winters and dry summers. This region includes Cambridge, London, Brighton, and Norwich.

South West

On the other hand, the tropical winds from the south ensure the South West UK has warm and wet summers and rainy winters, with an extended growing season. This region includes Cornwall, Bristol, Devol, and Cardiff.

North West

The North West UK experiences cool summers and mild winters, with the maritime winds bringing heavy rainfall throughout the year. This area encompasses Northern Wales, Northern Ireland, and Western Scotland.

North East

Lastly, the North East UK is infamous for biting winters and cool summers, thanks to the Arctic winds and steady rains throughout the year. Thus, the growing season here is also short. This region includes York, Newcastle, Aberdeen, and Edinburgh.

Month-by-Month Grow Guide for the UK

Harvesting cannabis

With the above climatic segments in mind, let's look at how your cannabis cultivation will look during a growing season. 

March (Avg. Temperature: 3 to 30 Degrees Celcius)

March marks the beginning of spring — the perfect time to start your cannabis cultivation. During this month, the conditions are still pretty cold in most regions, but you can begin cultivating indoors to get a headstart and end by winter.

So, get some LED lights and a suitable container and start germinating your seeds. You can even place your seedlings on a windowsill but ensure it gets enough sunlight during the day.

After starting your seed germination, you can begin preparing the grow area. If you're cultivating on the ground, begin by de-weeding. Then, apply high-quality compost to the soil. Straw or wood chip mulch works best to prevent weeds' growth and trap moisture.

If you are growing in a container, purchase some high-quality soil and apply a thin layer of compost on the top.

You can also start setting up your polytunnel or greenhouse this month if you want to. But, first, ensure the greenhouse or polytunnel does not have any algae on it and clear out the debris.

The climate may be warmer in some pocket regions, like Anglesey, Scilly Isles, or Dungeness. If you are lucky, you can plant your seeds directly in the soil. If you do this, stay up to date with the forecast reports and decide if it's worth the risk. We recommend keeping a backup crop in your house, too.

April (Avg. Temperatures: 5 to 13 Degrees Celsius)

During this month, the climate will improve across the UK, and the daylight hours will increase, bringing nice warm weather. However, in some regions, you must be careful of frost.

In most regions, you will still have to keep your plants indoors for a couple of weeks. But if you are using a polytunnel or greenhouse, you can move your plant outdoors safely.

The watering regime becomes crucial at this point. Thus, water the plant only when the soil dries out to avoid overwatering. Remember, the plants will still survive if water just a little. In fact, they will appreciate it. However, they will die a quick death if you overwater them. 

You should also look for weeds around your plant as they may suck vital nutrients from your plant. This is why it's crucial to de-weed right at the beginning. However, weeds keep returning, so de-weeding frequently is essential. 

You can also plant other companion plants around your cannabis plant to avoid weeds and pests and attract friendly insects. The best companion plants for the UK climate are yarrow, marigold, coriander, and peppermint.

May (Avg. Temperatures: 8 to 16 Degrees Celsius)

Come May, and the days will become much longer. In most regions, your plant will be ready to grow well. But in the central areas of the UK, you might have to wait until the third week of the month. And on the coast, the frost will depart by the end of the first week.

Now is the right time to move your plant outdoors, and still, containers are the best option. Some regions are more prone to sub-zero nights or frost, so containers are better as you can move them indoors easily. 

On the other hand, in South East and South West, you must keep your greenhouse or polytunnels ventilated because there may be a slight risk of heatwaves that can harm your plant. 

Once the frost has passed by the second week, you can transplant your seedlings into the growing area, whether it is a container or soil bed. 

In some northern regions, you may experience heavy rainfall. You can either move the container indoors or erect a tarp over the plant to keep it from drowning. 

And in the southern regions, you will not experience a lot of rainfall. This month is also an excellent time to set up drip irrigation so that you don't have to worry about watering your plant manually every day in the coming months.

Ensure that you water the plant well to keep it hydrated. But, again, don't overwater them. And you should also add some mycorrhizal fungi to the soil to support root development and nutrient uptake

Old compost may have broken down entirely, so you can add another layer of compost and worm castings. These will slowly release beneficial nutrients into the root substrate throughout the plant's vegetative phase. Your best options for this are seaweed fertilizer, compost tea, or other soil supplements.

If you haven't done so already, you can also add companion plants like chamomile to ward off pests. And if your region has a lot of mammal activity, you should also consider adding a fence or netting to protect your plant.

June (Avg. Temperatures: 11 to 19 Degrees Celsius)

During June, the summer will make its bold entrance. The daylight hours will increase, the temperatures will rise, and the risk of frost will have passed entirely, except for a few regions of the Scottish Highlands.

The weather conditions during this month are ideal for the cannabis plant, so it will start growing tall and wide significantly. The plant's requirement for nutrients and water will also rise as the plant grows bigger, so you will have to upgrade your nutrient and water regime.

In the North East and South East regions, the rainfall might dip. Therefore, ensure your irrigation system or watering regime is set to balance the potential water shortage. The best time to water your plant is in the early morning or evening for the best results.

Watch out for weeds this month and remove them as much as possible. In addition, add more mulch if required. 

Your plant will have grown enough to handle the training by the end of the month. You can try training methods like LST to keep the plant short and wide to avoid unwanted attention.

July (Avg. Temperatures: 13 to 22 Degrees Celsius)

The summers will peak in July, so your plant will enjoy the longest days and hottest temperatures. Thanks to the right conditions, your plant will grow more prominent with new leaves sprouting and the roots growing deeper into the soil.

In the North West regions, you can expect rainfall of up to 300 mm, enough to water your plant. However, the rain will be less in other areas, so you must ensure you water your plant correctly, especially if you are using a greenhouse. 

During this month, you should also inspect your plant for any nutrient deficiencies, like yellow, drooping, or curled leaves. And keep an eye out for common pests like aphids and whiteflies. If the population is low, you can remove them by hand or use other pest control methods like organic pesticides or beneficial insects.

Don't forget to train your plant during this month, too. You need to keep the canopy low to avoid unwanted attention and good light exposure. You will also have to make adjustments to the canopy by the end of the month so the plant is ready to enter the flowering stage.

August (Avg. Temperatures: 13 to 21 Degrees Celsius)

August is the final month of the summer season, so the daylight hours and temperatures will start to go down. And your plant will pick up on the cue and enter the flowering stage. 

Once your plant enters the flowering stage, it will require higher levels of potassium and phosphorus and lower levels of nitrogen. So, you need to upgrade your nutrient regime to give your plant the right amount of potassium and phosphorus.

We recommend using kelp meal, bone meal, or worm castings during this time, which will slowly release essential nutrients into the soil. You can also add more supplements like calcium, potassium, and magnesium to your water.

You may also face high humidity during this month, with humidity levels going up to 90% in some regions, leading to mold growth within your new buds. So keep an eye out for mold, keep your greenhouses ventilated, and pour water on the ground, not the flowers, to avoid mold.

Defoliation also works well to prevent mold as it improves the airflow within the canopy and increases light exposure of the buds within the canopy.

September (Avg. Temperatures: 11 to 18 Degrees Celsius)

During this month, the daylight hours and temperatures will continue to dip, and the buds will be close to maturity. 

As the buds mature, the terpenes will spread their aroma, attracting unwanted pests and attention. Fortunately, if you have planted companion plants, they will cover the aroma well. Plants like chamomile and lavender will also be ready to harvest during this time.

As the month progresses, fast-flowering strains will grow closer to maturity. We recommend flushing the plant with water a couple of weeks before harvest. 

In the western regions of the UK, you can expect 100 to 500 mm of rainfall. That's not an issue, so let nature water your plant for you. Keep a tarp close by to cover your plant if the rains prolong. 

And in the eastern parts, the rainfall will be scarce, so water the plant adequately.

October (Avg. Temperatures: 8 to 14 Degrees Celsius)

During October, the temperatures will dip further, and the trees will start shedding their leaves as autumn arrives, marking the end of the growing season.

If you're growing longer-flowering strains, keep them ventilated, watered, and defoliated. 

Most of the UK will experience heavy rainfall this month, but in Northern Ireland and other western regions, you should continue watering your plant manually. And in Central England, Central Scotland, and south of London, be careful of frost and inspect your buds for any signs of mold. 

Your plant will be ready to harvest by the end of the month. Finally, the result of all that hard work is right in front of you — pat yourself on the back for a job well done. Cut the flowers, dry and cure them, and enjoy your buds. 

The Legality of Growing Cannabis in the UK

UK legality

Unfortunately, the UK is lagging behind the rest of Europe in terms of cannabis legalization. The government classifies cannabis as a Class B substance, and possessing cannabis can quickly land you in jail for five years, an unlimited fine, or both. And growing and supplying cannabis can land you in prison for up to 14 years.

However, things are improving. CBD products are available throughout the country in various stores if they don't contain more than 0.2% THC. That's slightly less than the usual 0.3% limit in the USA but definitely better than a blanket ban. Even doctors are allowed to prescribe cannabis products to treat various conditions.

But if you want to grow legally, you must get a commercial license, which can be quite expensive. The permit costs £580 with an added extension of £326. And you need to prove that you are growing for commercial purposes and provide information on seeds, THC content, et al.

Despite the legality (or lack thereof), many growers still grow cannabis for personal use but discreetly. So, if you want to grow, you must grow secretly and in low quantity.

We recommend growing only a couple of plants. Then, if the authorities still catch you, you will mostly get a warning from the cops. Although arrest and prosecution are at your local police department's discretion, they decide how harsh your prosecution will be.

Avoid growing more plants, especially over nine plants, because the authorities will classify you as a contraband supplier, which is a Category 4 offense. It will invite the full force of the law against you.

So, it is best to grow only a couple of plants during a growing season and keep your plant as discreet as possible. This will help you stay safe from the law.

Summary: Guide to Growing Cannabis Outdoors in the UK

Growing cannabis outdoors in the UK is possible — all you need to do is take care of your plant, follow a strict timeline to match the weather conditions, and be discreet. Follow the above calendar to grow your cannabis plant.

You can start germinating your seeds by March and move the plants to the soil by April or May. Follow the correct watering and nutrient schedules, keep your plant safe from heavy rains or frost, and keep your plant safe from pests and mold.

Apart from these points, keep your grow small to keep it discreet and only grow one or two plants at a time to avoid harsh punishments. You should also never sell your buds because it might attract harsh punishments if you get caught.

Growing cannabis is a rewarding process and comes with various fun challenges to tackle. If you want to take your love for cannabis to the next level, start growing outdoors in your backyard discreetly. 



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