Learn how to germinate seeds quickly, with instructions for seed starting mix and DIY paper pots to get seedlings off to a healthy start.
Starting seeds at home enables gardeners to cultivate strong plants that are ready for the ground come springtime, while also bringing the joy of gardening indoors during the more dormant time of year. Luckily, you don’t need to spend much money on seed-starting kits and supplies. With just a few containers, homemade seed-starting mix, and some paper, you can grow excellent transplants for your garden.
Start the Seeds
Begin growing your seedlings in a controlled environment using a sterile medium. You can do this in a variety of ways. Peat pellets – compressed, dried circles of peat – have been prevalent in the gardening market for a while. Though inexpensive and simple to use, they also pose environmental issues. If you want an alternative kind of pellet, consider ones made from coconut coir. To forgo pellets altogether, create compost, sterilize it, add it to a seed-starting mix, and then use soil blockers to make a molded mound of soil to germinate seeds.
It’s possible to omit this step and plant directly into 3-inch pots with good results. Generally, bigger seeds are easier to start directly in pots, as they germinate quickly, while smaller seeds could be washed away and sit at the surface, which dries out quickly.
With any seed-starting method, pay close attention to the instructions on your seed packet, as that’ll inform you of what conditions your plants need to germinate and grow successfully and the best practices for sowing seeds. Understand the plant’s needs, including humidity, heat, water, soil conditions, and sunlight, before you place the first seeds into the soil.
After planting, cover the seeds and soil with plastic or glass (some seed-starting trays come with their own plastic lids), and place them in a warm and well-lit area. As soon as the seedlings emerge, remove the cover and place the seedlings in a sunny spot – ideally, somewhere they can get eight hours of sun – or under a grow light. If some seedlings haven’t sprouted yet, you may need to separate the germinated seedlings into an uncovered container while leaving the remaining ones covered. Throughout this seed-starting process, keep the soil and seeds moist. Only water when soil surfaces begin to look dry.
Transplant seedlings into 3-inch pots when a few second (“true”) leaves appear.
Do You Need a Heat Mat?
Some seeds need higher temperatures than others to germinate, so you may need a heat mat to supplement that additional warmth. For instance, lettuce will germinate at 40 degrees Fahrenheit, but carrots prefer 55 to 65 degrees. Tomatoes like 70 degrees, but eggplant won’t germinate until closer to 80 to 90 degrees, so it’ll need a heat mat if your house isn’t 80 degrees.
Consult your seed packet and evaluate the temperature where the seeds will be germinating to determine whether they need a heat mat. You can find effective heat mats on the market for roughly $25 for an 8-by-20-inch mat.
Replant the Seedlings
I’ve achieved my best results by planting seedlings into small pots and then replanting them into larger pots as they grow. This allows for maximum root development while ensuring the plants always have the right amount of growing medium without any unused soil that could harbor diseases and fungi or increase the risk of root rot. After one or two months, many blooming annuals will start to blossom, and tomato plants will be about 8 inches tall with their first blossoms that’ll develop as the plant grows larger.
Replanting times and plant sizes vary. Here’s a system that works well for me: When the seedlings show their second leaves, transplant them into 3-inch paper pots. First, I cover the surface I’ll be working on with newspaper to avoid a mess. I fill paper pots halfway with seed-starting mix. Then, I carefully place the seedling in the half-filled pot (if using pellets, remove the netting ). I fill the edges with more soil mix, lightly tamp it down, and water.
Depending on the crop, some seedlings will need to be replanted a second time, because they’ll likely get root-bound in the first container unless you plant them directly into the garden by then. The procedure for replanting the second time is the same, only you’ll use 4-1/2-inch-diameter paper pots. Plant tomato seedlings deeper than they were in the first pot; plant other seedlings at the same level. Carefully unwrap the seedlings from the previous paper pots before planting in the second, because although paper easily biodegrades outside, it won’t biodegrade indoors in the seed mix, which lacks the bacteria and organisms needed for decomposition.
Transplanting Outside
Around the last frost date (the specific timing depends on the crop), your seedlings should be ready for transplanting into the garden. Harden the transplants beforehand by gradually exposing them to the outside conditions in a protected place starting about 10 days before planting. Also, check the weather forecast to make sure there won’t be any dips in temperatures that could harm the plants. It’s better to wait several days than to risk ruining the transplants. Water the plants and garden bed several hours before planting. In early spring, plant in the morning so the plants have time to adjust before the cooler night temperatures set in. In late spring, summer, or fall, plant on a cloudy day or in the late afternoon so the plants will have some time to adjust before the midday sun.
To plant, dig a hole as deep as the plant’s root ball and a little wider. Tomatoes are best planted deeper. You can plant the paper pots directly in the soil, as they’ll quickly biodegrade. Lightly firm the soil, and water. Your transplants should grow to produce beautiful blooms and abundant harvests!
Make Your Own Seed-Starting Mix
The heart of seed starting, the soil mix, is one of the most important parts of growing your own seedlings – and also one of the most expensive. By making your own soil mix, you can grow seedlings with good results and minimal cost. The following mix can be used for seed starting, replanting, or even potting soil for container plants. Typically, I can make 40 quarts of seed-starting mix for $24.
To start, you’ll need cheap potting soil, perlite (sold at some stores and garden centers), and a small plastic net (such as the plastic netting from grocery-store onions). Potting soil with perlite provides good drainage, absorbs moisture, and has an even and light texture.
Notably, your seed-starting mix should be sterile so it won’t harbor any disease organisms that could infect your plants – or, if you give away any seedlings, other people’s gardens. (One method to sterilize soil is to put 3 to 4 inches of soil in a baking pan, cover with foil if moist, and bake for about 30 minutes at 180 degrees Fahrenheit, or until the soil temperature is higher than 160 degrees.)
First, sift the potting soil to remove large pieces and make it light and airy. To do this, cut one side of the plastic net to make an opening. Using gloves, put several handfuls of potting soil into the net. Close the opening with your hand, and shake the net over a tray to sift the soil. Sift inside a large bag to avoid creating a mess. Some clumps and wood chips will remain in the net. Empty them into another bag; you can later use them as mulch. Repeat with another batch of potting mix until you’ve sifted the amount of soil needed. Then, mix in the perlite at a ratio of 1 part perlite to 4 parts sifted potting soil. After mixing the ingredients, you’ll have a wonderful seed-starting mix.
Mixing It All Together
In addition to being sterile, a homemade seed-starting mix can have some nutrition to help seeds develop after their first couple of weeks. (When first sprouting, a seed has all the nutrients it’ll need within itself.) A cheap potting soil, if too cheap, may not have quality nutrition, in which case, consider adding sterilized compost to your mix.
Make Paper Pots
Paper pots are free, and you can make as many as you need. Unlike plastic pots, paper pots decompose, so you won’t need to wash and store them after planting. You can use newspapers or paper bags from the grocery store. And if you make a lot of them while your seedlings develop, you’ll have plenty ready by replanting time.
To make paper pots, you’ll need paper; scissors; and a cylindrical object, such as a bottle or a jar with a diameter of roughly 3 inches (4-1/2 inches for larger pots).
Cut the paper into rectangular pieces, about 17 inches long by 6 inches wide. These measurements will work well for sturdy paper; thinner paper may need to be longer. Take the bottle or other round cylinder and, starting on one end of the paper, roll the bottle while wrapping the paper around it. After that, slide the bottom edge of the paper about 1-1/2 inches below the bottle, and fold it over the bottle’s base to create the bottom of the pot.
Press the bottle’s base onto a flat surface to solidify those folds, and then slide the paper pot off the bottle. If the paper on the bottom keeps unfolding, push it from the bottom exterior with your fingers, and then press it down again using a bottle from inside the pot to solidify those folds. To make 4-1/2-inch pots, repeat the procedure using 22-inch-long and 9-inch-wide pieces of paper and a roughly 4-1/2-inch-diameter bottle.
Store Leftover Seeds
Most of the time, you’ll have leftover seeds from planting. Properly stored seeds can last much longer than those just stored in the packet. If storing at room temperature or in the fridge, keep the seeds in their packet and place them in a container, such as a cardboard box, along with a small amount of moisture-absorbing silica gel, available at most craft stores. If freezing your seeds, cover them in plastic and keep in an airtight container to protect them from condensation from when they thaw later on. Avoid leaving seeds exposed on a humid day, as this could drastically reduce storage life.
Seed-Storing Tip from Mother
How can you tell whether the seed-storage environment is effective? Here’s an equation to help, suggested to us by Baker Creek Heirloom Seed Company: humidity plus temperature.
If the humidity percentage plus the temperature of a specific spot doesn’t exceed 100, the seeds can be stored there without reducing viability.
Samuel Feldman is a farmer and writer, by both hobby and profession, who’s currently researching new crops and agricultural techniques. His work has been published in multiple publications, including Farming Magazine, AcresUSA, and Countryside.
