10 key parameters to create the optimum growing conditions for your outdoor plants

Genetics

Choosing the right cannabis strain for an outdoor grow is paramount. Depending on your location and climate, you may be limited in your choice. Growers in warmer climates have a little more freedom when it comes to choosing, as mild winters and long summers provide the ideal growing conditions for cannabis.

However, if you're going to grow your cannabis plants in colder climates, with fall rains that arrive as early as late September, it is best to choose varieties with a short growth cycle, that is, strains that can be harvested during the second half of September. And if you live in a region where the mild weather only lasts for 2-3 months, which translates into a short outdoor season, your best option will definitely be to choose autoflowering cannabis seeds.

Temperature

It is vital to have a good understanding of the climate in your area. Cannabis adapts really well to different growing conditions, but it is susceptible to extreme climates. If the temperature continuously exceeds 86°F, your plants will suffer enormously; whereas sustained temperatures below 50°F can also cause damage and delays in growth. This means that the best growing temperature ranges between 59 and 77°F. Cannabis plants can still survive out of this range, but temperatures below 41°F can quickly damage most cannabis strains. So if you live in a region where frosts in late spring or early fall are fairly common, try to use a greenhouse or another sheltered enclosure.

Wind

A constant breeze is great for cannabis plants as it helps strengthen their branches, thus making them more resistant to the weight of the buds. But if you live in an area where strong winds are common, consider placing your plants near some sort of windbreak, such as a wall or some big bushes; or you can simply place some plastic sheets on garden stakes around the plants. This will prevent branch breakage and overall stress. Nonetheless, the best option is always to use some type of trellising, especially if the plants are very big. This ensures that the branches are always supported and can easily withstand their own weight.

Rain

Rain sometimes comes in handy in outdoor grows, but growers generally see it as a bother. Rain can severely damage your plants and encourage the appearance of mold and fungi, especially during the blooming period. You can build a DIY greenhouse or simply use some plastic sheets on stakes to create a temporary refuge that you can easily place over your plants when there's a forecast of rain.

Humidity

When you grow outdoors, humidity control is not in your hands. The ideal relative humidity level (i.e. the amount of water present in the air in relation to a specific temperature) differs from one variety to another. Plants that are native to warm and tropical regions grow better with high humidity levels than plants from cold or warm areas.

Optimum humidity levels also vary according to the state of growth. For instance, seedlings need higher levels (between 70 and 80%) so they can focus all their resources on the development of a vigorous radicular mass. During the vegetative phase the humidity level needs to remain high but slightly lower than at the beginning (between 60 and 70%), whereas this should range between 50 and 60% at the start of the blooming phase, and between 40 and 50% during the second half of the flowering phase.

Sun

You also need to have a good understanding of how the duration of the day changes from one season to another. This is crucial so that plants can smoothly shift from the vegetative to the flowering phase. Generally speaking, cannabis plants love the sun, so they should receive as much direct sunlight as possible, ideally at midday, when light quality is optimum. As the summer season comes to an end with the arrival of the fall, the plants will receive less and less sunlight during the day, which will trigger the blooming phase. The angle at which the sun rays hit the surface of the planet is also a factor to take into consideration. This angle varies according to the latitude of the region. For instance, south-facing locations in Northern Hemisphere regions will receive more light, whereas in the Southern Hemisphere it would be preferable to grow in a north-facing garden for exactly the same reasons.

Soil

You can plant directly in the soil or prepare your own substrate. Cannabis plants require a well-drained soil that is rich in organic matter.

• Heavy clayey soils drain slowly and don't retain oxygen very well, so they require the addition of compost, manure, worms, or other decomposed organic matter, which are a good source of nutrients and also improve aeration and drainage.
• Sandy soils are easy to work with. They drain well and warm up quickly, but don't retain nutrients too well, particularly in rainy environments. Once again, you'll need to add compost, peat or coco coir to solve this issue.
• Silty soils are a mixture of the two previous types. This type of soil is usually found along the riverbanks, and constitutes the perfect growing medium for cannabis plants: it's easy to work with; it retains moisture well; it has a good drainage capacity; and it's rich in nutrients.

pH

The optimum pH values for cannabis plants range between 6 and 7. However, there are slight differences between these according to the different phases of evolution: the optimum pH values for the growth phase range between 5.8 and 6.2, whereas these can be higher during the blooming phase (up to 7). These parameters facilitate nutrient intake so that plants can develop to the fullest, something that they struggle with when the pH values are above or below these figures.

Irrigation

Even if you're growing outdoors, it is likely that you'll need to water your plants frequently, especially during the hot summer months, because the high temperatures and the winds will force them to transpire at a faster pace. Best to water in the morning so that plants have a good supply throughout the day. You need to be careful, though: excessive watering is a common mistake amongst novice growers. The general rule is to water generously and then wait until the top 5 cm of the soil have thoroughly dried before watering again.

Plagues

Without a shadow of a doubt, plagues are one of the biggest concerns when growing cannabis outdoors. You can always use pesticides to keep insects away, but if you want to obtain a truly organic product, it is best to fully plan your grow by including companion plants like basil, chamomile, dill, lavender, etc. Some of these plants attract beneficial insects, whilst others keep predators at bay. In addition, most of them enrich the soil, which in turn promotes growth.

Another alternative is opting for biological pest control methods, i.e. using insects that attack and eat harmful insects. This is a natural remedy that is simple to apply and prevents the use of chemical pesticides. In order to apply this method successfully, you need to be aware that every species that can attack your cannabis plants needs to be fought with its appropriate antagonist. For instance, you'll need a good army of ladybirds to get rid of a plague of aphids, whereas spiders are the favorite food of lacewings.

Last but not least, please remember: if this is your first time growing outdoors, there's no doubt that everything won't go smoothly. But don't forget that practice makes perfect! So make sure you don't become discouraged by any of the challenges ahead... Nobody became an expert grower overnight!