Starting (and saving) seeds tie us back to tending nature in ways both empowering and humbling. On a more practical level, growing your garden from seed provides a major cost savings. A packet of seeds is usually less than the cost of a single, small-potted vegetable or herb start. Add perpetual savings if you can save the seeds that you grow. However, seed-starting equipment can add up fast. Like all things gardening, we recommend starting small!
There are countless varieties of seeds to choose from compared to the limited variety of plants available to purchase in nurseries. You can select seed for differences such as cold tolerance, days to maturity and colors (to name a few).
A common mistake new seed starters encounter is starting them too soon, myself included! Many companies suggest a number of days or weeks prior to your average last frost date for starting seeds. For my growing zone, 4b, the typical last frost date is generally mid-May, but this date is changing due to climate chaos. You can also start seeds a little earlier if you plan to transplant them out into the garden under cover.
A typical seed-starting schedule for different seed packets will have you starting seeds as early as 10 to 12 weeks prior to the last spring frost, to just two to four weeks prior.
There are endless options out there for indoor grow lights and, like with most things, you get what you pay for. You can get regular fluorescent “shop lights” which are less expensive up-front, but there are specific benefits to different kinds of lights, including light quality (the wavelength or color) that mimics natural sunlight’s full spectrum and intensity.
For the general homesteader starting most plants, a full spectrum light of around 240 watts, or 5,000 Kelvin should do well. We use T5 LEDs and have been happy with the results. Keep in mind that a more efficient light bulb will produce more light with less watts of energy.
A common complaint with seed starting is ending up with leggy plants. Placing the lights as close as possible to the seedlings helps keep them strong. Setting a timer so your lights can stay on between 16 to 18 hours per day is a good idea, too. Plan for enough space under your lights as your plants grow taller.
Before you get planting, sanitize the pots and trays you’ll be using for seed starting by washing in hot soapy water and scrubbing off dirt, then soak in a bleach solution for a few hours (for an 8 percent bleach, use around 1 tablespoon per 1 gallon of water). Rinse well and let air dry. This is an important step to fight the problem of seedlings damping off, which is when seedlings die back at the soil level due to fungus and bacteria in the soil.
The industry standard size for seed-starting trays is called a “1020” which is roughly 10-by-20 inches. Please stay away from the super flimsy plastic trays. Think about how heavy pots will be with ready-to-transplant seedlings before your purchase. You can repurpose plastic containers or buy new pots.
Soil blocking has been around for years but is gaining popularity because it grows great seedlings. Using a soil-blocking press, you pack soil into squares and press out a firm block of soil, removing the need for a pot. You then plant seeds directly into this block of soil. It holds itself together, creating the perfect environment for seedling roots to “air prune” and eliminating the problem of root-bound seedlings. This process reduces transplant shock and makes it nearly impossible to overwater.
I use a solid 1020 tray with a mesh 1020 tray nestled inside for my soil block seedlings. There is still plastic involved, but the process is more sustainable overall.
There is no single best temperature for seed germination, as it depends on the seed. There is a huge variation, with peas germinating in 45-degrees-Fahrenheit soil and beans preferring around 70 degrees, but in general, you’ll get a higher germination rate and quicker germination with the use of a heat mat, especially for many of the plants we typically start early: tomatoes, peppers and eggplant. Heat mats are simple waterproof plug-in units that fit under a regular 1020 tray.
Always start seeds with a sterile seed-starting mix. Don’t use regular garden soil or previously used potting mix, as these can harbor bacteria and fungus that can kill seedlings. There are many brands of seed-starting blends available, but I like to mix up my own blend.
I get compressed bricks of coco coir which yield roughly 2 1⁄2 to 3 gallons from one compressed brick after soaking it in water and letting it expand for a few hours. Be aware that perlite dust isn’t great to breathe in so mixing this outside or dampening the perlite before mixing is advised. See my recipe for soil blocking and seed starting in “DIY Seed-Starting Mix ” below.
Seeds require air, water and the right temperature to germinate. In general, seeds give you clues on how deep to plant them from their size. The bigger the seed, the deeper to plant. Tiny lettuce seeds get pressed into the top layer of soil, while bean seeds get pushed much further down into the soil. A general rule of thumb is to plant twice the depth or width of the seed size. Keep in mind some seeds need light to germinate, while others require darkness. Your seed packet should state any specific instructions. I like planting into already dampened soil and watering them in with a gentle sprinkle of water.
After sowing and watering seeds in, you’ll want to keep them warm and damp to help germination. The simplest way to do this is to cover them. We’ve all seen the clear plastic domes to help keep in the humidity but reusing a piece of plastic wrap works just as well. Remember to remove any cover as soon as you see green popping up! Keeping the soil and emerging seedlings covered too long invites mold—a seedling’s worst enemy.
Just like watering plants in the garden, you’re going to want to water the soil, not the leaves. And since we’ve got them in trays, we can even water from below.
Watering from below helps water evenly and fully, so you’ll also water less often, which is better for root development. Watering from below also decreases “splash-up,” the chance for fungal and mold (damping off) problems.
There are systems you can set up for this, but I still prefer to hand water because it gives me a chance to check on each tray. Let the top layer of soil dry out a bit, and keep in mind that more seedlings suffer from being overwatered than drying out!
The most important part of seed starting is simply paying attention to them daily. Luckily, this is also the part that brings gardeners the most joy: Tending to their babies, watching the daily growth, and responding quickly.
Tips for Keeping Seedlings Growing Well
Adding a fan will both help air flow, which will keep pests and diseases down, and strengthen plant stems. If you don’t have a fan, gently run your hands over the plant tops to mimic the movement.
When fertilizing seedlings, use a diluted (50 percent strength) form of organic fertilizer once a few sets of true leaves are present, and only every four-plus weeks after that, if you haven’t transplanted them out by then.
Pinching off top growth and/or buds will help some seedlings (such as flowers and peppers) grow stronger and produce more buds.
If your seedlings get pests (such as aphids), try spraying them off with the stream setting on a spray bottle or take them outside and use a gentle hose setting. Make sure to set a fan in front of the seedlings to help them dry off as well. Air flow in general is helpful in seed starting.
Fungus gnats are becoming more and more prevalent in our seed-starting mixes. To combat, water with a diluted hydrogen peroxide mix (2 to 3 tablespoons per 1 gallon of water), top pots with vermiculite, use yellow sticky traps, and if they continue to get worse, consider watering or spraying the soil surface with a Bt (Bacillus thuringiensis) product. Bt is a naturally occurring bacteria that, once ingested, kills targeted insects.
You can also bake soil to kill any adults or immature fungus gnats. It’s sort of stinky, baking soil, but it works. Set the oven temperature between 175 and 200 degrees Fahrenheit (no hotter than that), spread your soil in a thin layer on a cookie sheet, and bake for about an hour.
Moldy soil is another growing problem. I don’t usually have this problem, maybe because I don’t tend to overwater. I do know that mold likes warm, damp environments so removing heat mats and letting the soil dry out a bit will help. You can scrape off the soil with the mold on it, and then water with a diluted hydrogen peroxide mix.
Hardening off is an essential part of growing healthy vegetable plants from seed. You’ll need to slowly acclimate your seedlings to the full power of sunlight, wind, and changing temperatures. Find a partially shaded spot that’s not too prone to wind gusts and start by bringing the plants out for fifteen to thirty minutes the first day, increasing from thirty to sixty minutes per day for at least a full week. Try to avoid the noon hour for the first few days as well. Not giving them enough time to acclimate can give them “sun scald” and set the plant’s growth back by days or weeks.
Once fully acclimated to the outdoors, you can transplant when the soil is warm enough for the crop; as this varies depending on the crop, refer to the seed packet. Both soil and air temps need to be warm enough. Now is the time to check out that garden plan you worked so hard on!
I often transplant my tomatoes, peppers and other heat-loving plants out under cover, giving them a little warmer soil and air and added protection against lower overnight temperatures. The best transplant day is a cloudy one, but putting up a shade cloth helps lessen transplant shock. I fertilize at time of transplant with a slow-release fertilizer, or a balanced mix containing N-P-K (nitrogen, phosphorus and potassium/potash) ratios like 3-3-3 or 4-4-4.
When you transplant plants that looked so big in your seed-starting area into the garden, they tend to look tiny. They’ll also take a day or two to bounce back from transplant shock. Try to give them (and yourself) some grace and appreciation. Remember that this plant was a tiny seed not that long ago. And trust in nature, knowing that your tiny tomato plant will end up taking up all the square footage you let it.
Best Seed Starting Tips
- Best to start indoors because they take a long time to get established: celery, eggplant, leeks, onions, peppers and tomatoes.
- Best to start indoors if you want an early jump (especially northern gardeners): broccoli, cabbages, cauliflower, chard, cucumbers, melons, kale, kohlrabi, lettuce and squash.
- Best to direct sow: beans, corn, carrots, peas, potatoes and radishes.
- Best vegetables for winter sowing: beets, broccoli, cabbage, cauliflower, chard, kale, kohlrabi, lettuce and spinach.
Excerpted by permission of Skyhorse Publishing Inc. Copyright © 2023 by Stephanie Thurow and Michelle Bruhn. Photographs © 2023 by Stephanie Thurow & Michelle Bruhn, unless otherwise noted.
Stephanie Thurow (minnesotafromscratch.com) and Michelle Bruhn are (forksinthedirt.com) are Minnesota moms who fell in love with homesteading in very different ways but found friendship through their shared passions for real, local food and their DIY hearts. Find out more about them on their websites.