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how to start a cannabis greenhouse from seed

Pre-flowers can initially be extremely small and hard to identify with the naked eye, but you can use a magnifying glass to get a better look.

After completing these steps, it’s time to wait. Check the paper towels once a day to make sure they’re still saturated, and if they are losing moisture, apply more water to keep the seeds happy.

Keep a close eye on the temperature and moisture level of the soil to keep the seed happy. It’s very delicate at this stage. Use a spray bottle to water it—over-watering can suffocate and kill the delicate sprout.

Can I grow a seed I found in a bag of weed?

Autoflowering seeds are also popular with beginning growers. They are easy to grow because you don’t have to worry about light cycles and how much light a plant receives.

You might also find a mature seed that has been physically damaged through poor handling, like rough trimming. In those cases, it probably isn’t worth the effort to try and germinate the seed.

Many marijuana growers start autoflowers early in the season, and at a different time than a regular crop, so keep the season and climate in mind when growing and harvesting—your plants still need warmth to grow, and rain can give them bud rot. Consider growing in a greenhouse to protect them.

This is the beauty of seeds—often, you can tell which plants or genetics will thrive right from the get-go. This will help you determine which plants you want to take cuttings from for clones or for breeding if you want to create a seed bank of your own.

Growing photoperiod feminized cannabis is also possible in a greenhouse, but comes with some constraints, especially if you’re using exclusively natural light. As these strains flower based on the hours of light they receive, you rely on the seasons to support vegetation and stimulate flowering.

In addition to allowing you to flower your weed at any time, blackout covers also serve to prevent cannabis light pollution (e.g. nearby street lighting), which could otherwise interfere with flowering for photo-feminized plants.

Growing cannabis in a greenhouse is ideal because it combines the benefits of outdoor growing with those of indoor cultivation. In this guide, we’ll show you how to do it, offering tips and advice as we go along. If you don’t have a greenhouse yet, and want to build one, we can show you how to do that, too.


Cannabis strains differ in how they grow, and in regards to their requirements. The best type of cannabis for your greenhouse setup ultimately depends on a number of factors, including your local climate, available space, and whether you’re planning to use an artificial grow light. Let’s dig in a little deeper:

With natural light as the main source of energy in your greenhouse, you need to plan your grow window accordingly. Ideally, you want to be ready as soon as daylight hours (and temperatures) start increasing in spring.

Autoflowering cannabis is optimal if you’re growing using natural sunlight. As autoflowers don’t require a set light schedule to veg and flower, variations in sun exposure won’t harm your plants or diminish yields as much as photo-feminized plants. This also means you can plant and harvest autos in your greenhouse at any time of year—as long as you support ideal environmental conditions.

Unlike outdoor cultivation, a greenhouse protects your plants from the elements. There is no threat of rainfall or storms harming your precious ladies. In addition, a greenhouse prevents scavenger animals from having their way with your crops.