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how warm should it be to plant marijuana seed

Growers who only have a few plants may not need a full-sized greenhouse. They can take advantage of the same principles on a smaller scale by building cold frames. Cold frames are small boxes made out of lumber, usually 2×4’s, and glass. Since they’re so small, there’s really no reason for growers to skimp on the glazing and as a result, cold frames typically provide better insulation than plastic-clad greenhouses.

Temperature isn’t the only thing growers should carefully control during the flowering stage. They should also reduce the humidity levels in their grow rooms to between 35 –45% for the early flowering stage and lower it even further to 30% for the last few weeks before harvest. Lower humidity reduces the risk of serious problems like bud rot, mold, and powdery mildew.

Excessively cold temperatures can also negatively impact plant growth, even if it isn’t cold enough in the grow room to kill the plants. While the plants will still photosynthesize and produce sugars, they won’t be able to move those sugars to where they need to go if they’re too cold. This begins to be a problem when the temperature falls beneath 68°F. Mature plants will store the sugars and move them when it warms up, but young plants can be stunted by prolonged periods of cold.

Patio Heaters

Plants in veg also require a different lighting schedule, and most growers tailor their temperature ranges to that schedule. Most experts recommend 18 hours of light followed by six hours of darkness for plants in veg. When the lights go off, growers should set the temperature in their veg rooms 10 – 15° cooler to encourage increased growth, but don’t let the temperature fall below around 60°F, especially while the plants are young.

Hot compost produces more heat than most growers expect. At the height of decomposition, temperatures can peak at between 120 – 150 °F. Growers who add thermophilic compost piles to their greenhouses should make sure they’re prepared for that outburst of heat, which begins just one day to one week after finishing and watering the pile by adding adequate ventilation.

Even those who plan to grow outdoors shouldn’t try to dry or cure their weed outside. Instead, they should construct a small drying room and follow the temperature and humidity recommendations for indoor growers above to the best of their ability. Unless they’re growing completely off-grid, providing some extra climate control shouldn’t pose a problem.

As far as hybrid strains go, Silver Haze, Northern Critical, Blue Cheese, White Widow, and Somango are all popular with growers who live in colder climates. Outdoor growers certainly shouldn’t constrain themselves to growing only these strains, but they at least offer a good place to start.

Often overlooked, it is all too easy to assume that the vegetative and flowering stages of cannabis growth are the most critical parts of the plant’s life cycle. However, with the chance of failure high unless you know what you’re doing, poor planning when it comes to germination can make or break your next grow. Giving your cannabis seeds the best possible start on their journey to bulging buds is a surefire way to encourage a healthy and robust plant.

Before we jump straight into the germination methods, there are a couple of germination golden rules. For the best results, we recommend staying within these guidelines, no matter how you choose to germinate. That being said, of all the factors to consider, temperature is one of the most critical. Seeds will always seek out even the smallest amount of moisture, but they use temperature as a sign that they need to do so.


Arguably one of the least effective methods, but it is still viable. Incredibly simple to facilitate, beginner growers may opt to germinate their seeds in a glass of water. Half-fill a glass or bowl with water that is approximately 22°C (71°F).

The dome of the plastic container will create your seeds’ own mini tropical climate. If you then place all the components in a temperature-controlled cupboard, you will have created a self-perpetuating supply of moisture—no need to touch the seeds again until they are ready to be transferred to your final growing medium as a young seedling. Using the stone wool block method, your seeds should germinate in one to two days.