Tips for Early Season Greenhouse Growing

By Kent Gruetzmacher
Published: May 8, 2023
Presented by AC Infinity Inc.
Key Takeaways

Many argue that growing cannabis in a greenhouse is a challenging endeavor but it’s even harder in the early season. Given that, there are several things to keep in mind when growing weed during the early season in a greenhouse.

Many people feel greenhouse cultivation is the most difficult type of cannabis growing to master. Not only must you understand technology like inline fans and grow lights, but you must also account for the dynamic swings of the outdoor climate. When you grow greenhouse cannabis in the early springtime, these challenges become even more apparent.

With the promise of warm weather right around the corner, outdoor growers are often eager to get their plants outside in the sun when springtime finally arrives. While there are many benefits to moving your plants into a greenhouse as early as April, there are some specific steps you need to take to ensure they are cared for.

No matter where you live, nearly all outdoor growers start clones and seedlings indoors during the winter. Whether your operation is full-sun or greenhouse, the sooner you get plants outside, the quicker you can cut back on the expensive costs of running grow lights.


Why Grow Cannabis in a Greenhouse in the Early Spring?

flowering cannabis in a greenhouse

There are multiple reasons why growers opt to get their plants into greenhouses in the early spring months.

If you are growing full-sun outdoor plants, putting them in a greenhouse in the spring will give you a major jump on the season. You can get the tedious process of hardening off your plants out of the way before the sun gets really intense. When daylight hours get long enough, you can simply move your plants into larger pots and let them go.

Light deprivation is another reason you’d want to get your cannabis crop into a greenhouse in the early spring. With light deprivation, growers “trick” cannabis plants into flowering by creating 12 hour intervals of day and night with blackout tarps. By starting your light deprivation operation early, it's possible to produce two to three greenhouse crops in a single outdoor growing season.


What is Unique About Early Season Greenhouse Growing?

The most important environmental factors to consider when setting up your greenhouse in the spring are temperature and light.
In most regions of the United States and Canada, the early spring months can present extremely mixed weather conditions. While it's not unusual to have 70°F days in locations as far north as Chicago in April, temperatures often dip below freezing as well. This notion is particularly true during the nighttime when there is no sunlight hitting your greenhouse. As such, heat sources are a major consideration for early season greenhouse cultivation.

Total hours of available daylight are another critical environmental factor to consider with early season greenhouses. In places like New York state, you can count on the sun rising at around 6:30 a.m. and setting at about 7:15 p.m. in the month of April. With spring daylight hours so close to 12-hour intervals of day and night, you need to utilize supplemental lighting in your greenhouse to keep plants from being triggered into flowering.

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How to Heat Your Greenhouse in the Early Spring

greenhouse thermometer

If you are a hobbyist grower, you have several easy options for heating your greenhouse during cold snaps in the early springtime.


CO2 Burner

If you already use a CO2 burner in your indoor garden, it's simple to repurpose this tool as a greenhouse heater in the spring. If you have an atmospheric controller in your greenhouse, simply set it so your CO2 burner to kick on when it gets below a certain temperature threshold—such as 50°F. It’s also possible to simply connect your CO2 burner to a timer so it turns on during the coldest hours of the night.

Portable Heaters

Portable heaters are another easy and affordable way to heat your greenhouse in the springtime.

If you prefer propane, you can go with a basic “sunflower style” heater. However, beware that these heaters have open flames and they must be manually turned on and off. For something a bit safer, you can also look at propane heaters that are designed for tent camping.

It's also an option to use an electric patio heater in your greenhouse. If you decide to go with an electrical heat source, just be sure that it is engineered to safely work in outdoor environments.

Extending Daylight Hours with Supplemental Lighting

supplemental grow lighting

In order to keep plants in the vegetative growth phase during the short daylight hours of the spring, you must add supplemental lighting to your greenhouse. Please note, the goal here is simply to keep plants from flowering, not stimulate growth by means of artificial light. As a result, you don’t need very powerful grow lights to get the job done.

Fluorescent Lights

Due to their affordability and ease-of-use, many growers opt to use simple fluorescent lights for supplemental lighting in the springtime. If you already have some T5 lights on hand for clones and seedlings, you can easily use them in your greenhouse to extend daylight hours and keep your plants from flowering.

LED Light Strips

LED light strips are another great option for greenhouse lighting in the springtime. In fact, the Ionbeam Series LED Grow Light Bars from AC Infinity are the perfect supplemental lighting choices for small greenhouses. A single Ionbeam Series kit includes a lighting controller, four LED grow light bars, and four steel bars that allow for easy mounting on variable surfaces.

There are many reasons to get your cannabis plants outside into a greenhouse in the early spring months. Not only can you get a jump on your full-season garden, but you might be able to pull off another full round of light deprivation if you see fit. In either case, using sunlight to fuel your garden in the early spring is a surefire way to save on electricity. While there are many good reasons to get your greenhouse started early, that doesn’t mean that this type of cannabis growing is easy.

If you plan on getting your cannabis plants into a greenhouse as early as April, it’s a good idea to research your local climate to be better prepared. Even more, keeping careful tabs on the weekly forecast will help you properly anticipate large temperature fluctuations. Once you have a good feel for the local environment, you should have tools on hand like heaters and supplemental lighting, so your plants receive the proper care.

AC Infinity is the foremost name in air delivery systems, designing and developing the latest innovations in cooling and ventilation technology. They offer a suite of quiet inline fans that automate the growing progress and track key metrics. Visit or contact [email protected] to learn more.


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Presented By

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Written by Kent Gruetzmacher | Writer, Owner of KCG Content

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Kent Gruetzmacher MFA is a Colorado-based writer and owner of the writing and marketing firm KCG Content. Kent has been working in the cannabis and hydroponics space for over a decade. Beginning in California in 2009, he has held positions in cultivation, operations, marketing, and business development. Looking specifically to writing, Kent has worked with many of the leading publications and marketing agencies in the cannabis space. His writing has been recognized by such icons as Steve D’Angelo and Rick Simpson.

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