How to Design an Indoor Grow Room to Get a Gardening Head Start

Maybe you’re one of the millions of people who took up gardening during the pandemic or a long-time home gardener who’s ready to plant before the final frost. Growing plants indoors is a great way to jumpstart your outdoor garden and grow herbs, veggies, and your favorite house plants throughout the winter. Let's explore how to create a grow room of your own, whether you plan to take over the whole basement or set up a mini-greenhouse on the bookshelf.

Why Should You Start Plants Indoors?

Even if you're new to gardening, you know that all plants have a few basic needs. Plants need light, water, and air to survive. Dig a bit deeper and you'll learn that plants grow best when they get the proper nutrients from their soil and live in balanced humidity and temperature.

Growing plants outside in the elements can be tricky to time. Plant seeds or seedlings too early, and they could shrivel up in an unexpected frost. Start them too late, and they may not have the chance to bloom—or produce salad-ready produce—before the first frost in the fall.

Starting plants indoors gives you a bit more control. You have the power to mimic the cycles of natural light and ensure proper temperature, humidity, and airflow. You can also protect plants from harsh elements during their early, delicate germination stage.

What is a Grow Room?

The term grow room may sound a little intimidating, but don't get us wrong. You don’t have to redesign an entire room to start seedlings indoors or support light-hungry plants through the darker months of the year. Plant room ideas run the gamut from a corner in your basement to a glass cabinet with added LED lights. 

A grow room—or area—has:

• A light source: You will need natural light from the windows, grow lights that mimic warm and cool light, or a combination of both. For this reason, you'll also need either access to an outlet or battery-powered lights. Some indoor gardeners add a timer to mimic the cycles of the day as well.

• Temperature and air control: A space heater or fan will keep air flowing and temperature even throughout the space.

• Humidity control: Consider containing plants in a closed cabinet or control the airflow of the room itself.

• Accessible storage: It should be easy to access your plants to provide them with regular waterings and to check their soil. Opt for a shelf with enough space for your plants to share the light and expand over time. Bookshelves, counters, and cabinets with glass windows work best.

You can also purchase a grow tent and kit specially designed to balance your plants’ environment. Grow tents range in size and can fit in small closets or take over an entire walk-in closet.

Now, if you’re daydreaming about your very own freestanding greenhouse, don't hold back. Just make sure you hire a local greenhouse specialist to lend a hand.

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Setting Up a Grow Room

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Designing the ideal grow room truly comes down to the plants you intend to care for. If you're bringing your potted plants in from the porch or simply hoping to keep your ficus alive through a winter of dry radiator heat, you may not need a complex setup. Simply follow a few tips for keeping your houseplants happy in the winter. Keep the plants away from the radiator, cold window glass, and in as much direct sunlight as possible.

But what if you want to grow an indoor herb garden or start vegetables from seed before the outdoor planting season begins? Here are some basics to start seeds indoors and inspire consistent indoor garden growth.

Get to Know Your Plants

Germination times, light preferences, and preferred humidity differ from plant to plant. Read the instructions on your seed packet or seedling case for these details. If you're starting vegetables from seed, be sure you choose plants for your hardiness zone and ones that will transfer easily out of their pots—which we'll touch on below.

Prioritize Light

In some cases, a southern-facing window with full-day sun will be enough to encourage plants that benefit from either medium or low levels of light. Growing vegetables from seeds, however—particularly light-hungry plants like tomatoes and bell peppers—will need extra help from a grow light.

Grow lights mimic the spectrum of daylight that a particular plant needs. While you can technically use traditional fluorescent and incandescent bulbs, LEDs or full-spectrum lights are more effective because of their similarities to natural light. Further along in your grow room journey, you can narrow in on red, blue, or green-spectrum lights to encourage specific responses from your plants.

Set your grow light on a timer to shine between 12 and 16 hours a day, depending on the age of your plants and level of natural light in your room. 

Adjust Temperature if Necessary

Have you ever spent a lot of time in a greenhouse? It's a bit like a low-key plant sauna. The optimal temperature of a grow room is between 65 and 80 degrees Fahrenheit and humidity levels between 40% and 70%. Both of these ranges are common in your everyday home, but a persistent radiator can make the humidity plummet.

Opt for Seed-Starting Soil

Keep in mind that starting seeds outside of the earth requires additional nutrients. Choose a potting soil marked for starting seeds and encouraging seedlings. The soil may contain some percentage of developed compost or you can add your own. Ensure the soil drains well while still holding moisture.

Best Plants to Start Indoors

The Farmer's Almanac recommends starting slow-growing vegetables indoors to ensure they produce a full harvest in your growing season. This is particularly important if you live in a colder region with only four or five months of frost-free weather. Great candidates for indoor grow rooms are:

• Tomatoes

• Bell peppers

• Eggplant

• Broccoli

• Brussels sprouts

• Cabbage

• Cauliflower

• Celery

• Lettuce

Herbs like basil, rosemary, and parsley also grow well indoors and can even flourish in grow rooms or sunny, balanced spots year-round.

Transplant When the Time is Right

In most cases, you'll start vegetable seeds in your grow room between four and six weeks before the final frost in your region. Hardy, cold-weather plants like broccoli and brussels sprouts can head out first, but sensitive plants like tomatoes should wait until nighttime temperatures stay above 50 degrees.

Seedlings raised indoors will also need some toughening up before heading outside to avoid shocking their systems. Begin the "hardening off" process one to two weeks before the transplant. Decrease the temperature of your grow room by lowering light levels or letting in more cool air. You can also slowly introduce potted plants to shaded areas outside for a few hours each day.

The transition will seem second nature after a season or two of swapping between your grow room and garden. Until then, don't be afraid to call a gardener in your area for tips on starting an indoor grow space or the best way to get a head start on your garden the right way