The Beginner’s Guide to Starting Vegetable Seeds Indoors

The Beginner’s Guide to Starting Vegetable Seeds Indoors

By Amy Dvorak
Dreaming of your own veggie garden, but not sure where to start? Here’s how to sprout vegetable seedlings right on your windowsill.

It’s an almost indescribable feeling: that moment mid-summer when you’re feeding your family fresh, delicious food that you grew from mere seeds. Not only is it incredibly rewarding, but it will also taste better than anything from the grocery store. However, it doesn’t come without a little trial and error—and a whole lot of patience. "For the new gardener, if you’re starting with seeds, there are a lot of challenges, and there is a lot to learn," says Kyle Hagerty of Urban Farmstead. To learn how to navigate a new garden, we caught up with Hagerty and other green thumbs around the globe.

When starting from seeds, Kyle Hagerty from Urban Farmstead suggests a variety of simple, DIY methods. "Some use egg cartons, some people use plastic Solo Cups, paper pots out of newspaper, or used egg shells," he says. "But at most nurseries or hardware stores—and of course online—you can order seedling germination containers or trays."

Figuring Out When—and What—to Plant

Forget the containers. Forget the compost. When it comes to vegetable gardening for the first time, it all starts with a calendar. As many regions have only a few months that are frost-free, understanding your climate and growth window is step one. "A lot of gardening starts even before you get soil or a tray," says Hagerty, whose instructional gardening videos cover everything from soil tests to irrigation systems.  

While all seeds will have different instructions on the packets, a general rule of thumb is to start sowing seeds indoors six to eight weeks before your last frost date. Let’s say you missed that window. What happens if you start sowing anyway? We’ll walk you through that scenario using the trusty tomato.

Large varieties of tomatoes have a lengthy time to mature. Start seeds early for vegetables with longer maturity times or opt for nursery starts if you've missed the window.

It’s late May, and you spin the wire display rack in search of beefsteak tomato seeds. It will take two weeks for seedlings to sprout, and then another few weeks before they reach the right height to be transplanted into the ground. Add 10 more days to harden them off (we’ll dive into that later), and we’re well into July. That’s the point when you can finally calculate "days to maturity," which you will also find on the seed packet, indicating the date you’ll be able to harvest your crops. For that beefsteak tomato, it could be 80 to 90 days. That brings us to September or early October: you haven’t even seen your first tomato, and the fall frost is looming. 

It may be too late for that varietal based on your zone, but not to despair. "If you realize you missed the boat now, you can start planning for fall what you want to grow, and start researching now," says Jasmine Jefferson, founder of Black Girls with Gardens, which provides gardening support, inspiration, and education for women of color. For planting this season though, she suggests some quick-growing options like lettuce, radish, beans, peas, and herbs, which mature in less than two months. "Whatever you plant, start small," she says. "That is the number one thing. You don’t want to be overwhelmed. There are going to be failures, and you don’t want to be overwhelmed by them. Master what you’re doing, then take it to the next step."

Jasmine Jefferson founded Black Girls With Gardens and Black Men With Gardens to represent, educate, and inspire people of color in the gardening world, and is soon launching a coach program.

Sowing Seeds

Once you’ve selected your seeds and have a good grasp on your growth window, you can dive in and start to sow. "You can buy seed trays and cells, or for a more sustainable option, you can use yogurt containers, toilet paper rolls, or even egg cartons; just make sure it has drainage holes," says Lee Sullivan, who runs the Urban Veggie Patch account on Instagram. At her home in Australia, she became interested in gardening after the birth of her child, seeking a more sustainable and healthy lifestyle. "At the same time, I was experiencing mild postnatal depression (I like to refer to it as postnatal depletion), and unexpectedly, growing and gardening helped me to heal from that," she says. "It is incredibly rewarding, and I love knowing that my family is eating homegrown, nutritionally dense, organic produce." 

Hagerty and his dog, Burdock, harvest vegetables from their home in California. A firefighter by day, Hagerty is an avid home gardener and operates a neighborhood food stand when he's not filming gardening tutorials for his YouTube channel.

To ensure the most nutrient-rich environment for your new seeds, she suggests using a seed-raising mix, never dirt from your yard. Plant your seeds at about double the depth of their own size, which won’t be very deep. If the seeds are particularly fine, you can sprinkle them on the surface and then lightly cover them with the fluffy soil. "It is important to keep your seeds moist and within the temperature range they need for germination," she says. "If the soil dries out, it is likely that the seeds will not germinate." Seeds can take anywhere between five and 21 days to germinate, and once that occurs, she advises to put them in a place where they will get direct sunlight at least six hours a day. If you don’t have good light indoors, it’s common to supplement with grow lights, and Hagerty has even had success with more cost-efficient LED lighting.  

After a few weeks, you’ll start to see their first leaves, "but it’s not their true leaves," says Jefferson. She says to wait until you see the second set of leaves, at which time you can begin to feed your plants. "The best thing is to add organic matter like a compost or fertilizer," says Hagerty. During this phase, it’s more waiting and watering. Be patient as they begin to strengthen and gain height the next few weeks, a crucial phase before transplanting them into their summer homes.

"Just get out there and start gardening," says Hagerty. "Don’t be afraid to experiment with different things, but pay attention to what works and what doesn't. If it doesn’t work, know that you can always change it up next season."

Hardening and Transplanting Seedlings

One your seedlings grow about eight inches to a foot tall—and if weather permits (after the last frost date)—that’s when you can finally transplant them outside. But it isn’t a swift maneuver. 

An often overlooked step for first-time gardeners is hardening off the seedlings, according to Hagerty. "You have these seedlings that are used to being coddled in ideal conditions in the house for a couple of months," he says. "Once ready to plant in the garden, you can’t take them from the windowsill at 68 degrees and suddenly plant them in a garden where it’s 80 degrees by day and 50 at night. They are not happy as little seedlings. It has to be a slow transition." If your climate experiences great temperature fluctuations between day and night, you will need to bring the plantings outside to acclimate during the day, bringing them in nightly for about 10 days before planting. "The last thing you want is to put all this energy into seedlings, then everything dies because you missed an important step," says Hagerty.

Once you’re ready to transplant them—whether that’s into the ground, a raised bed, or containers, revisit the seed packet for spacing instructions. "With containers, you will need enough drainage holes so there’s no waterlog, and you don’t have to worry about roots rotting away," says Jefferson. "You just want to ensure the container is large enough. With tomatoes, that’s always at least 15 to 18 inches apart. You don’t want to overcrowd containers, so make sure to research proper spacing."

"There are some great advantages to growing your plants from seed," says Lee Sullivan, who runs the Urban Veggie Patch Instagram account from her home in Australia. "There is greater diversity in terms of what you can grow, and you have control over how the seedlings are raised, which is especially important if you are committed to organic growing." 

Considering Alternatives

While starting from a seed offers more variety and is satisfying to have accomplished, it doesn’t come without challenges. For those wanting to slightly jump ahead, Hagerty suggests exploring nursery starts. "It can be easy to get overwhelmed and frustrated," he says. "I would say, try some seeds and plan on also buying some seedlings from the nursery. For the most part, nurseries carry the most popular plants, and if it’s a good nursery, they will have varieties that grow well in that area. You can put them directly in the ground: it’s good to go, and you’ll have a sturdy, healthy plant." If you opt for nursery starts, he recommends getting the smallest plant as a cost-effective tip, as they grow quickly this time of year and are much more affordable than more mature starts. 

Modern Arch Propagation Planters from Vintage Revivals allow you to see roots growing. The company offers DIY templates so you can make the yourself.

Another thing gardeners can experiment with is propagation, or regrowing vegetables from cuttings or scraps. By doing this in water, it allows for a beautiful visual as well. "Propagation is just magical," says Mandi Gubler, the face behind Vintage Revivals. "All the seeds go through this process in soil, but you never see it. But when hanging on your wall, you can look over and see the roots grow, and it’s just the most beautiful kind of art you can put on your walls." Her company designs propagation planters for purchase, or you can access the tutorial and make them yourself. 

Before she got her green thumb, Gubler says she often bought plants, but they quickly died. "I finally realized that if you treat them like decor, they will die. They’re living things and need certain light and need to be taken care of to be given the best chance of survival," she says. But that doesn’t mean pushing yourself past the point of it being enjoyable. "Just figure out how to do it so it brings you happiness," says Gubler. "If it stresses you out and adds garbage to life, it’s not the right thing for you." 

Mandi Gubler (right) and her husband Courtney of Vintage Revivals and Happy Happy Houseplant.

Wherever you are in the journey, whether that’s killing plants or reviving stunted seedlings, Sullivan sums it up best. "Like many things in life, your first attempt may not be perfect, and it may not work out, but don’t let that discourage you," she says. "Gardening is a journey, and you will experience many failures and many triumphs. Learn from the failures and keep going!"  

"The challenge for me as a gardener is that there are so many different answers to everything," says Hagerty. "It's not that it's wrong, it's that there are so many variables." His advice: Consult your local garden center, know your climate zone, and read the seed packets. 

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