Starting plants from seed is an immensely rewarding experience that fills gardeners, young and old, with hope and joy.
Nothing beats the excitement of watching tiny seedlings emerge from bare soil on your windowsill, especially when the weather outside is cold, grey, and rainy. Seed starting indoors is a fantastic way to grow sturdy, site-adapted plants, including heirloom varieties of vegetables, herbs, and flowers that you won’t find as starts in garden centers.
To top it all off, seed starting is incredibly economical—you’ll end up with a large quantity of plants to grow in your garden, starts to share with friends, or leftover seeds to use in following seasons.
Indoor seed starting requires bright light, adequate moisture, high humidity, and a watchful eye. Our steps for starting seeds indoors provide a basic framework to help new gardeners and seasoned veterans approach seed starting with confidence.
1. Selecting Seeds to Plant in Your Garden
Shopping for new seeds, or trading seeds with friends, is one of the best things to do when Winter blues have you wishing for more time in the garden. Here are a few of our top tips to make sure you end up growing things that will work for you and your garden.
- Plant seeds for vegetables and herbs that you like to eat! Success is found not only in growing, but in enjoying the end result, so if you’re new to growing veggies or herbs, select things you know you enjoy eating!
- Plant seeds for edible plants with multiple harvest potential so you can enjoy them for many months, such as leafy greens, lettuce, salad mixes, and leafy herbs like basil, cilantro, or parsley.
- Plant flower seeds that you want to cut! Make selections that complement your existing color scheme, attract pollinators, or add fragrance and summer interest.
- Check your old, unused seed. Most seed is good for at least three years, though larger seeds such as corn may not last as long. If using old seed packets, it is wise to do a germination test before mass planting.
Visit one of our garden centers or shop online to see the seeds we have available at each of our Portland area nurseries. Dennis’ 7 Dees is proud to carry seeds from two excellent companies:
Botanical Interests: Since 1995, Botanical Interests has been supplying gardeners with the highest quality organic and conventional seed in beautiful and informative seed packets. Their desire to provide more information led them to create a unique seed packet that includes art, garden history, landscape ideas, organic gardening know-how, recipes, fun facts, and high-quality seeds.
Lake Valley Seed: Lake Valley Seed was founded in 1985 and sources seed from all over the world to provide gardeners with affordable conventional, organic, and heirloom seeds. All Lake Valley seeds are non-GMO and untreated (including no treatment with neonicotinoid pesticides).
2. Timing Your Seed Planting
The timeline for seed sowing is listed on each seed packet—it may be written as “Sow X number of weeks before last frost date.” April 10th is the average last frost date for the Portland metro area. Organize your seeds into groups by sowing date, and start sowing with those that take the longest to germinate and mature first.
Tomatoes, Peppers, and climbing annuals like Sweet Peas and Cobaea scandens are among the first plants you’ll want to sow. Reserve some of your tougher seed for direct sowing outdoors, including Poppies and Calendula.
3. Supplies Needed for Starting Seeds Indoors
Seed can be grown in simple conditions, but there are a few products you’ll want to purchase in advance to make your efforts more successful and get your seedlings off to a healthy start.
- Use a sterile seed-starting soil mix, jiffy pots of dehydrated coir, or coir bricks. Add in 10% soil from your raised beds or vegetable patch to help introduce beneficial bacteria and fungi to the seeds right away. However, adding garden soil may also introduce weed seeds, so keep watch!
- Use biodegradable pots that can be directly planted in the ground such as jiffy pellets, peat pots, newspaper pots, or even eggshells. Plant 2-3 seeds per pot, and remember to mark each pot with a label.
- Use seed starting trays to mass sow varieties of plants before pricking them out and planting them in the garden or larger pots.
- Grow lights are a great way to add supplemental light to your growing areas, and are essential if your home doesn’t have bright windows with all day sun… or if you happen to live in the PNW!
- Heating mats will help speed up germination and make sure that small seedlings don’t suffer from cold, overly wet soil.
4. Planting Your Seeds Indoors
Once you’ve gathered your seeds, double checked timing, and have your supplies ready to go, the real fun can begin! Planting seeds is easy, meditative, and a little bit magical.
- Prepare your soil blend and pre-moisten it to help the seed stay in place. Some seeds, especially large, hard-shelled ones like sweet peas or garden peas, benefit from soaking in water overnight or for up to 24 hours before planting, however this isn’t critical.
- Fill your pots with soil and leave ¼–½” from the top without any soil so you have room to water.
- Plant your seeds at the proper depth, which should be listed on the packet. A good rule of thumb is to plant your seeds three times as deep as the seed is wide. It’s better to plant seeds too shallow than to too deep.
- Use your finger or a pencil to create a hole in your pot for larger seeds and fill it back in with the surrounding soil.
- For very small seeds, sprinkle them over the surface of the pot and add a small layer of soil over the top to cover them.
- Place seed trays where they will receive bright light, ideally in an east or south-facing window. Bright light is essential for germination and strong seedling development, so supplement your existing growing conditions with grow lights.
- Place a clear plastic dome cover over your seedlings to help hold in moisture and humidity. Be sure to remove the plastic dome and heat mat as soon as seeds have germinated.
5. Caring for Your Seedlings
Nurturing pots of bare soil until wisps of early leaves appear is a wonderful way to pass the time. Be sure to water, keep humidity levels high, and check in on your tiny wonders regularly.
Watering Seedlings
Keep soil thoroughly wet—water gently and consistently using a small watering can. A spray bottle is also useful for spritzing the soil surface and keeping seedlings hydrated. Place seeded pots in a solid-bottomed tray to prevent water from leaking through and damaging tables.
Once seeds have germinated, continue watering regularly, as roots will be very small and can dry out very quickly, killing the whole plant.
Seed Germination
Germination can take several days or several weeks depending on the type of seed planted, and you can check seed packet details for expected days from planting to germination. Bottom heat from a seedling heat mat can speed up the germination process but is not necessary for success.
Fun Fact: the first “leaves” to appear are actually the embryonic cotyledons that emerge directly from the seed. After the cotyledons, the seedling produces its first set of “true” leaves that more closely resemble those of the adult plant.
Fertilizing Seedlings
Use an organic liquid fertilizer diluted to ½ or ¼ strength. Wait to feed seedlings until seeds have germinated and grown their first set of true leaves. The begin feeding your plants weekly or every 10 days.
6. Transplanting Your Seedlings Outdoors
Once your seedlings have started growing, it may be tempting to move them right outside, but be mindful of outdoor weather conditions and soil temperature before making the big move!
- Reference seed packet or plant information for best time to plant outside for each variety.
- Check your soil temperature with a soil thermometer. Pay attention to nighttime temperature lows along with your last frost date.
- Wait until the seedling has formed at least two or three sets of true leaves at a minimum before transplanting into a larger pot or outdoors into the garden.
- Slowly transition seedlings outdoors—place them outside for increasing amounts of time over several days. If needed, use a floating row cover for protection from extreme sun, wind, and rain.
Starting seeds indoors can help revive even the weariest of winter gardeners and give them some hope for the gardening season ahead! Come visit Dennis’ 7 Dees Garden Centers and shop our fantastic range of high-quality seeds and seed starting supplies, or get friendly advice on starting seeds from our gardening experts!