Don’t Wait for Spring: How to Start Seeds Indoors Now for a Healthy Garden
Growing a bountiful garden doesn’t start when temperatures warm, flowers blossom, and birds start singing in the spring. No, a successful garden is won in the darkness of winter in your basement in February. It begins with seed starter soil, fluorescent grow lights, heating pads, and careful tending. Indoor seed starting is the key to a bountiful garden in the summer, but only if you follow the right strategy. We sought out advice from Jeremy and Staci Hill, gardening influencers and founders of Missouri-based Gooseberry Bridge Farm, and authors of The Preserver’s Garden, for help with indoor seed starting.
The Countdown to Indoor Planting
The biggest mistake people make when seed starting indoors is starting too early or too late, according to Jeremy Hill. “Timing is everything, you don’t want your seedlings to get too big for your indoor space, or not be large enough to go out on time,” he says.
Gather Intelligence
- Determine your last frost date: Make your best guess as to when the last frost date will take place in your area. Luckily there are online resources to help you do this. Sites such as The Old Farmer's Almanac and Dave’s Garden, can estimate your last spring frost date using historical data for your zip code.
- Backwards Count: Timing your indoor planting is key to making a successful transition from indoors to garden, but it also isn’t rocket science. Seeds require varying amounts of time to germinate and grow before transplanting. Tomatoes need six to eight weeks while peppers and eggplant need eight to 10 weeks. Once you’ve determined your last frost date, simply count back the number of weeks for your respective seed type to set your indoor planting date. Use the chart below for guidance.
Seed Starting Calendar
| Weeks Before Last Frost Date | Plant |
|---|---|
10-12 weeks | Onions, Leeks, Celery |
8-10 weeks | Tomatoes, Peppers, Eggplant, Parsley |
6-8 weeks | Broccoli, Cabbage, Cauliflower, Kale |
4-6 weeks | Lettuce, Spinach, Herbs, Collards |
2-4 weeks | Peas, Kale, Swiss chard, Brussels Sprouts |
1-2 weeks | Cucumbers, Squash, Melons |
Note: Root vegetables like carrots and beets hate being transplanted. Direct sow these veggies.
The Essential Gear for Indoor Planting
Having the right materials on hand for your indoor planting is key to success. Here’s what you need:
- Seed starting mix: The number one mistake newbies make is using garden soil to start their indoor planting. Garden soil compacts too easily and drains too poorly and will suffocate the roots of seedlings. If you want your seedlings to survive to bear fruit later, then you need a good seed starter mix. Seed starter is sterile, so there's no soil born diseases or weed seed in it. It’s also light and airy, allowing oxygen to reach roots and delicate seedling roots grow through it. You can make your own seed starter by mixing equal parts peat moss, perlite, and vermiculite or purchase a commercial seed starting mix, such as Miracle-Gro Seed Starting Potting Mix.
- Containers: You’ve got to grow your seedlings in something. You can go the DIY route to save money or buy a full kit. “Egg cartons, lunch meat containers, even cut up toilet paper tubes or rolled newspaper can be used to start seeds,” Hill says. Just make sure whatever you use has a hole in the bottom for drainage.
You can also go with all-in-one pellets, which combine the container and starter soil and includes a tray to hold them but Hill recommends doing it yourself. “Pellets are easy, but they don’t provide much space or fertility for your seedlings,” Hill says. - Light: Your seedlings need 14 to 16 hours of sun each day, which isn’t going to happen by simply setting them by the window, especially in winter when days are shorter and sunlight is weaker. Your seed starters need a fluorescent grow light to get the amount of sun they require to grow big and strong. Skip the overpriced grow lights and get a cheap LED shoplight, which works just as well.
- Heat Mats: If you want to maximize your seed germination success rates, get a heat mat. They’re essential if you’re growing peppers, tomatoes or eggplants, all of which require soil temperatures to be between 68 and 86 degrees fahrenheit to germinate. Since soil temperatures are 10 to 15 degrees cooler than air temperature, they are a must for germinating seeds. “If your room is 75 degrees then the soil temp could be 60 which is too cool for germinating heat loving crops in a timely manner,” Hill says.
Zoe Richardson on Unsplash
Nurture Your Seedlings
Once those little green hooks begin to poke through the soil, it’s time to move to supporting this fragile life.
- Incubate: Your seedlings need light and a lot of it. Position your LED shop lights so that they’re just 2 to 3 inches from the tops of the seedlings. Any further and you’ll encourage them to become leggy, a term used to describe when seedlings grow tall with thin weak stems. “These lights look bright to us but they are nothing compared to the sun, so they need to be very close to the plants at all times,” Hill says.
- Bottom’s Up Watering: Don’t pour water over the top of the seedlings. Instead, pour water into the tray and allow the soil to soak up the moisture from the bottom to the top. This practice helps to prevent damping off, the number one cause of death in seedlings caused by overly wet soil. Bottom up watering keeps the soil surface dry, preventing the mold growth that leads to damping off.
- Cull the herd: it may sound cruel, but for some seedlings must die so others can survive to adulthood. If you planted several seeds per cell, and more than one germinated, you’ll need to clip the weaker ones. Use a pair of scissors to snip the smaller sprout at the soil line. Don't pull them out as doing so can damage the keeper.
- Train your Sprouts: Run an oscillating fan on low over your seedlings for a few hours a day. The wind puts a small amount of stress on the stems, causing the stems to grow thicker and stronger. “You’ll also need to add some kind of fertilizer after the plants get a couple of sets of true leaves,” Hill says. Once you notice true leaves, the second set of leaves that appear after the sprout, apply a little liquid fertilizer diluted to 1/4 strength to avoid burning the roots.
Related: The Best Grass Seed for Clay Soil and How to Prep Your Lawn for Planting
Hardening Off Your Seedlings
Many people get their seedlings all the way through basic training only to see them wither and die in the battlefield of their garden. You can’t just transplant seedlings that have spent their life in a calm 70-degree environment and throw them directly into a cold harsh 55 degree garden and expect them to survive. “Grow lights are nothing like the sun, and the fan is nothing like real wind,” Hill says. “Plants will need some time to adjust to the harsher conditions outdoors.” Prep them for life in the harsh outside world with a little basic training by following this 10-day hardening off schedule :
- Days 1-2: Place your seedlings in a shaded area protected from the wind outside for 1 to 2 hours then bring them back inside.
- Days 3-4: Place them outside for longer, 2-3 hours, with some exposure to sun and wind.
- Days 5-7: Continue building them up by giving them 4 to 6 hours of sunlight. Watch them carefully for sun scald, a condition in which white patches appear on the leaves, and pull them in immediately if you see it.
- Days 8-10: Leave them out all day and night as long as temperatures stay above 50 degrees fahrenheit.
Transition Day
Once you’ve completed the hardening off period, it’s time to send your seedlings off into the real world by transplanting them in your garden. Check the weather forecast to make sure there are no surprise frost warnings, then move them to the garden. Staci suggests doing it on a cloudy day or in the late afternoon to give the roots a chance to settle in before taking a full day of sun.” In the event that it is extremely hot and sunny outside on transplant day, consider adding some kind of shade cloth, umbrella or tent for your seedlings,” he says.