When is the best time to germinate cannabis seeds and start an outdoor grow?

The arrival of spring is a particularly comforting time for outdoor cannabis growers. It signals the kick-off to start planning new growing adventures, which involves choosing the best Cannabis seeds and working out when to germinate them. But while growing marijuana outdoors can be a rewarding experience, the success of a grow largely depends on choosing the right time to start, which can mark the difference between weak and low-yielding plants and an abundant and healthy harvest.

Cannabis is a photosensitive plant whose life cycle is closely linked to environmental conditions, especially light and temperature. Germinating seeds and planting them at the optimal time ensures that plants enjoy an appropriate vegetative period before flowering, which translates into vigorous growth and abundant flower production. On the other hand, sowing at the wrong time can expose plants to adverse conditions, affecting their health and reducing their yielding capacity.

Factors that influence the decision on the optimal planting time

Cannabis is an annual plant species that naturally adapts to seasonal cycles. In most regions, spring is the ideal time to start, but the exact time may vary depending on your geographic location. Therefore, there are several factors you should consider:

Climate and seasons in different regions

Climatic conditions vary significantly by region, so adapting the growing schedule to these variations is essential. In areas with cold winters and warm summers, like much of Europe and North America, spring is the ideal season to start growing outdoors. More specifically, it is recommended to germinate the seeds between March and May, once the minimum temperatures consistently exceed 10°C.

In regions with a Mediterranean climate, characterised by mild winters and dry summers, the growing season can be extended, allowing sowing as early as late February. On the other hand, in tropical areas where seasonal variations are less pronounced, it is crucial to consider the wet and dry seasons, choosing to start cultivation at the beginning of the dry season to avoid problems associated with excessive humidity.

Hours of sunlight

Cannabis is a plant whose development is influenced by the duration of both day and night. During the vegetative phase, plants require long periods of light to grow properly, which means taking advantage of the months with more hours of daylight – these extend until the summer solstice (i.e., 21^st June, the longest day of the year), after which the hours of daylight start to decrease.

In the northern hemisphere, days begin to lengthen after the spring equinox (21^st March), providing ideal conditions for vegetative growth. It is important to synchronise the germination of the seeds with this increase in daylight hours to maximise the development of the plants. You should germinate your seeds so that the plants have enough time for their vegetative growth to develop before the summer solstice.

Day and night temperatures

Temperature is a critical factor in all stages of cannabis cultivation. During germination, it is recommended to maintain a constant temperature between 21 and 25°C to promote the appearance of the seedlings. Once transplanted outdoors, the plants will thrive in warm daytime temperatures (ideally between 22 and 28°C) and in night temperatures that stay above 15°C. Lower temperatures can hinder growth or even damage the plants, especially in the early stages.

Risk of late frosts

An unexpected frost may destroy seedlings or cause significant damage that affects their later development. It is therefore essential to ensure that the risk of frost has passed before moving the plants outside. In many regions, this safe period begins after specific dates that are popular locally; for instance, the “Ice Saints” in Central Europe, which are held from 11^th to 15^th May.

Specific germination recommendations for different climatic zones

Temperate climates (northern Europe): In these areas, which include northern France, Germany, and the UK, it is advisable to germinate the seeds in mid- to late spring, once the minimum temperatures exceed 10°C and the days are long enough to promote healthy growth.

• Germinate indoors: mid-April.
• Transplant outdoors: mid-May to early June.
• Objective: To avoid late frosts and take advantage of the rapidly increasing daylight hours.

Mediterranean climates (southern Europe): The mild winters of areas such as Spain, Italy, or Greece allow for earlier sowing. However, it is essential to be aware of possible heavy spring rains that could negatively affect the seedlings.

• Germinate indoors: early March.
• Transplant outdoors: late March to mid-April.
• Objective: To make the most of the long growing season and mild temperatures.

Tropical climates: Since light variation throughout the year is minimal, the planning of your grow should be focused on both the wet and dry seasons. Starting germination at the beginning of the dry season is ideal to avoid mould problems and other diseases related to excessive moisture.

• Germinate and plant: At any time, avoiding the heavy rain season.
• Consider: Strains adapted to equatorial climates with more constant light periods.

Protection of young seedlings in early germination

Germinating Cannabis seeds early can offer several advantages, including a longer vegetative period and potentially larger, more robust plants. Having said that, unstable early-season weather conditions can pose significant challenges for young seedlings, so you always need to consider ways to protect them.

The use of greenhouses or plastic tunnels is one of them. These structures provide a controlled microclimate that protects seedlings from low temperatures, strong winds, and heavy rainfall, whilst maintaining adequate relative humidity.

Individual covers or protective hoods are also welcome, with devices such as cut transparent plastic bottles that can be placed on top of each seedling, and which act as mini greenhouses that maintain the heat and protect them against possible frost.

Mulching is also a great idea. Applying a layer of organic material around the base of the plants helps maintain soil temperature and retain moisture, as well as reducing weed competition.

Nevertheless, starting the germination in a controlled environment at home and transplanting the seedlings outdoors when conditions are more favourable can significantly increase survival rates.

Influence of cannabis strains on the decision to germinate

Different cannabis varieties have specific characteristics that influence the optimal time for germination. For example, photo-dependent feminised strains, just like Go Fast genetics, depend on the length of the day to start flowering, so they require careful planning to maximise their vegetative period.

As a general rule, cannabis plants with predominantly indica genetics tend to flower faster, since they developed in the mountainous regions of Asia, where they needed to flower quickly before the return of the cold. Therefore, these strains can be planted later, which makes them ideal for northern climates with shorter summers.

Sativa genetics evolved in warmer equatorial regions which allowed them to enjoy long hot summers with plenty of sunshine. That’s why sativa strains tend to have longer flowering times than indicas, which means they require earlier germination, making them more suitable for sunny southern areas closer to the Mediterranean.

Finally, autoflowering varieties flower regardless of the photoperiod that they’re exposed to, and have shorter life cycles (usually between 8 and 12 weeks from germination to harvest). This allows for multiple harvests in a single season and offers flexibility as to the timing of sowing. If you play your cards right, by planting autoflowering varieties early in the season, you can fit in two or even three grows in a single cannabis growing season.

And remember: Patience is the mother of science

As you can see, choosing the right time to germinate your cannabis seeds and start an outdoor grow is a crucial decision that requires the consideration of multiple factors. But if you need a piece of advice that brings them all together, remember that patience is a virtue in cannabis cultivation: It’s always better to wait a little longer and make sure all conditions are optimal, than to rush and risk your entire crop.

With careful planning and attention to detail, you’ll be on the right track to a successful and rewarding outdoor cannabis grow. And whichever approach best suits your location, taste, and growing options, now is the time to start buying cannabis seeds that will allow you to make the most of the spring sunshine while you enjoy your plants growing all around you.