Growing cannabis from seed without lights

How to Grow Seeds Indoors Without Lights or Heat Pads

Whether it’s your first time or your 101st time, there’s something about growing seeds indoors that can evoke a childlike sense of wonder and joy in even the most passive personality. These are heady emotions, so you don’t want to let a little thing like starting seeds without a heat mat or light diminish your enthusiasm in any way. Instead, you’ll simply have to be extra vigilant about caring for your seedlings until you’re ready to plant them outdoors. It can be done, and you can do it if you’re willing to cast additional light on your planting repertoire.

Choose Your Seeds Carefully

You may be growing seeds indoors to get a jump on the growing season, to compound your fruit and vegetable harvest or both. Without the benefit of a heating pad for germinating seeds or a plant light, you must be extra choosy about the types of fruit and vegetable seeds you start indoors. The truth is that some plants would give you a hard time anyway, meaning that they would grow better if the seeds were planted directly into the ground without the risk of disturbing the roots.

Root vegetables like beets and carrots are notoriously fussy, so The Old Farmer’s Almanac recommends planting these other fruit and vegetable seeds indoors instead:

  • Broccoli
  • Brussels sprouts
  • Cabbage
  • Cauliflower
  • Eggplant
  • Lettuce
  • Peppers
  • Pumpkin
  • Swiss chard

Even if you were going full tilt with a heat mat or light, it would be a good idea to anticipate a few losses. So, plant a few more seeds than you had originally planned.

Compensate for a Heat Mat for Seedlings

As you may know, growing seeds indoors occurs in two phases: germinating, when the seedling literally “pops” from the seed, and growing. During the first phase, your seeds will need warmth more than light. To compensate for the lack of a heat mat for your seedlings, plan to put your seedling tray in a room where the temperature ranges between 65 and 75 degrees Fahrenheit. Then, set the tray in a place that provides consistent and gentle warmth, such as the top of a refrigerator or portable freezer (as long as it’s stable).

After leaves begin to sprout from the seed and they grow to about half an inch tall, they will need more light. Without it, they should grow, but they will be thin and gangly. To fortify your seedlings in this phase, place the tray on a sunny, south-facing windowsill, says Burpee. Just remember to rotate the tray every day or so. A plant that is arching toward the sun is a good sign that it’s time to turn the tray in the opposite direction.

It may also help to remember that as much as you think you’re working at a disadvantage without a light or heat mat for your seedlings, overwatering is actually the No. 1 reason that seedlings fail to grow.

Sow Your Seeds

As a rule of thumb, most seeds should be sown indoors about six weeks before the last frost in your area. Gather your seedling tray, peat pots or even an egg carton and follow these planting tips from Family Handyman. First, fill each opening with all-purpose potting mix. One made specifically for seeds is ideal since it is lighter than regular potting soil and is easier for seeds to push through. Make a shallow depression in the soil with your fingertips or the eraser at the end of a pencil.

Sprinkle a few seeds at the depth recommended on the seed packet and then cover the seeds with more soil. Water until the soil is thoroughly moist and then cover the tray with clear plastic wrap to trap the moisture inside. Place the tray in the warm spot you’ve selected. Apply a liquid fertilizer once a week to fortify the seedlings. Once the seedlings emerge, you can remove the plastic wrap for good.

If you’re growing a variety of fruit and vegetable seedlings, keep in mind that they won’t mature at the same pace. Some will grow quickly, while others will play catch-up, mimicking another childlike phenomenon that makes gardening so rewarding.

Can you grow cannabis indoors without lights?

Many hobbyist growers elect to use grow tents, closets, or other enclosed spaces when growing cannabis indoors, often outfitting these spaces with lights and even humidity and temperature control systems. Depending on your level of interest and enthusiasm, these systems can cost anywhere from hundreds to thousands of dollars.

But can you simply stick a cannabis plant in a nice sunny window and let it do its thing? Read on to understand what to expect if you choose to grow cannabis indoors au naturel, along with a few tips and tricks from experts to help your indoor plant thrive in a minimal setup.

The environment inside your home is perfectly safe for your cannabis plant. Photo by: Gina Coleman/Weedmaps

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Is my home a suitable environment for cannabis?

The environment inside your home is perfectly safe for your cannabis plant. It offers all the same basic benefits you enjoy, like warmth, oxygen, protection from the elements, and light.

“I make zero effort to control the climate of my grow spot. If you’re growing without a light, that plant will be just fine in regular household conditions that are suitable to us humans,” explains Jimmy B Harvests, a YouTube creator that documents his adventures in growing cannabis, along with other fruits and vegetables, at home.

What to expect when growing weed indoors without lights

Will growing a plant indoors without grow lights leave you with wonky plants? Lower yields? Less potent flower?

Not necessarily. “The more effort and energy you put into a plant, the bigger and better your harvest will be,” said Jimmy. “I think that’s a pretty universal truth in the gardening game, but I’ve definitely been surprised by how well plants can do without the elaborate tents, fans, filters, feeding systems, and so on.”

Successfully growing a cannabis plant indoors is all about covering the plant’s basic needs: air, light, temperature, water, and nutrients. So, if you get those things right, your homegrown cannabis plant could provide much more than a fun experiment. And considering that indoor cannabis plants can grow a few feet tall and equally wide, you should anticipate young plants to take up more space by the time they reach maturity.

Cannabis plants need plenty of bright light or direct sunlight. Photo by: Gina Coleman/Weedmaps

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Make sure your cannabis plant gets enough light

Cannabis plants need plenty of bright light or direct sunlight. Southeastern and southwestern exposures provide the most direct sunlight per day, followed by southern, eastern, and western. If you’re dealing with a northern exposure, your cannabis plants won’t have enough direct light to thrive. You’ll need to supplement with artificial light.

To maximize the amount of daily sunlight your plant receives, work with the seasons. The total number of daylight hours vary depending on where you are, but in the Northern Hemisphere a good rule of thumb is to germinate your seeds around the Spring Equinox.

Bottom line: Sunrooms, rooms with lots of southern-facing windows, and bay windows are all great spots for indoor cannabis plants. Aim for at least six hours of direct sunlight per day.

There are two types of plants a grower might consider: autoflowering varieties or photoperiod varieties. Photo by: Gina Coleman/Weedmaps

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Autoflower vs photoperiod plants: what’s the difference?

There are two types of plants a grower might consider: autoflowering varieties or photoperiod varieties.

Photoperiod plants need to follow a specific light schedule, particularly during the flowering period. These plants need 12 hours of complete darkness to induce flowering and throughout the flowering phase until harvest. “If you can’t get the environment dark enough, that plant is just going to keep on growing and might get too big for the space you have,” added Jimmy. Our homes are full of light, so to assure the darkness needed to induce flowering, put the plants in a closet each sundown and back out in their window each morning.

Autoflowering plants begin flowering automatically based on their maturation. When they reach a particular age, they flower, regardless of how much sunlight/darkness they are getting. These plants do not require the complete darkness that photoperiod plants do, meaning you could leave them out and about overnight and they will be fine. Another reason you might want to choose an autoflower variety is if you’re short on time since their growth cycle is shorter than it is for photoperiod plants.

Bottom line: Photoperiod plants will require several months of your time and attention, whereas some autoflowering plants complete their life cycles in as little as 49 to 56 days. This is something folks might not consider when getting started with cannabis — you have to tend to it often and be present through the plant’s life cycle. So if you’re planning a vacation or work might take you away from home, an autoflower strain might make more sense for you.

When growing in your home’s natural environment, choose a strain that will best match up with the general temperature and humidity of your mango-colored home. Photo by: Gina Coleman/Weedmaps

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Consider your indoor climate when choosing a strain

One reason indoor growers work so hard to manipulate the growing climate with light-, temperature-, and humidity-control systems is that different cultivars have different needs and preferences.

When growing in your home’s natural environment, choose a strain that will best match up with the general temperature and humidity of your home. If you use air conditioning in the summer, then you might want to select an indica-dominant cultivar that can thrive in milder temperatures. If your home is hot and humid during the summer, then a sativa-dominant strain might be a better choice.

Experience is the best teacher when it comes to growing cannabis. Photo by: Dimitri Newman/Weedmaps

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Tips and tricks for your indoor grow

Experience is the best teacher when it comes to growing cannabis — or any plant for that matter. Consider these tips before embarking on growing weed indoors without lights.

Keep it simple to start. When it comes to your setup, “I would challenge people to try doing as little as possible on their first plant and adding in effort or equipment only to solve issues as they arise or to better future plants,” shared Jimmy.

Be a good plant parent. Keep an eye on its growth and development. Trim yellowing or dying leaves that often present at the bottom of the plant when they get shaded by the top canopy. Keep an eye out for insects and act quickly when you see them, then continue monitoring closely because pests and disease can be persistent and difficult to get rid of.

Rotate your plant. “Growing with just a window, your plant is going to bend itself towards the light constantly and will benefit from regular rotating. I was rotating my cannabis plant twice a day to keep it growing relatively upright,” said Jimmy.

Pro tip: don’t set your cannabis plant on fire. Photo by: Dimitri Newman/Weedmaps

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Flush your plant before harvesting. If you’ve been feeding your plant with synthetic nutrients or fertilizers, you’ll need to give it a good flush before harvesting. By flushing the growing medium of nutrients and fertilizers, you’ll leave the plant to use up its reserves before harvesting. It’s an important step that, if skipped, can negatively impact the final quality of your flower. Timing is important here because you don’t want to strip your plant of nutrients too early. One to two weeks before harvest is a good rule of thumb.

Keep a grow journal. There are many ready-made journals tailored specifically for growing cannabis. You can also grab a pad or notebook and jot down daily details on watering, feeding nutrients, the days or weeks in a particular growth phase (vegetation, flowering), any insects or mold issues, and so on. Having a record of a plant’s full life-cycle will help improve future plants.

Bottom line

Managing your expectations is important, especially if this is your first attempt at home growing. Caring for and mastering the art of growing cannabis is something that takes years of experience. With time, attention, and a keen eye for detail, you can improve your outcomes with each new plant you grow, even with no lights and a minimal setup.

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