Starting plants from seed is an immensely rewarding experience and an economical way to grow a garden. There are several clear advantages to growing plants from seed:
- Access to a wide selection of plant varieties
- Stronger plants that are conditioned to your environment
- The ability to use seed that was collected and stored from previous years, passed from neighbor to neighbor, or came from other regions
- Intimate knowledge of where your food and flowers came from
In early spring, many gardeners have small seed trays lining their windowsills, kitchen counters, and tabletops. Seeds that were planted in blank soil emerge a few days later, first as wisps of green cotyledons followed by “true” leaves, adding millimeters of stature and growing stronger as the days lengthen. This is a ritual that brings hope and a bit of excitement to the grey, rainy days.
Indoor seed starting requires bright light, adequate moisture, high humidity, and a watchful eye. The guidelines below provide a basic framework to help new gardeners and seasoned veterans approach seed starting with confidence.
How to Select Seeds to Plant in Your Garden
- Most seed is good for at least three years; 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.
- Plant seeds for vegetables and herbs that you like to eat! Success is found not only in growing, but in enjoying the end result.
- Plant seeds for edible plants with multiple harvest potential, such as leafy greens, lettuce, salad mixes, and leafy herbs like basil, cilantro, or parsley.
- Plant flower seeds that complement your existing color scheme, attract pollinators, or add fragrance and summer interest.
Timing for 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.
Seed Starting Soil & Planting
Use a sterile seed-starting soil mix, jiffy pots of dehydrated coir, or coir bricks, and be sure to pre-moisten the soil before planting. Adding in 10% soil from your raised beds or vegetable patch will help introduce beneficial bacteria and fungi to the seeds right away, but may also introduce weed seeds, so keep watch.
Use biodegradable pots that can be directly planted in the ground such as peat pots, newspaper pots, or even egg shells. Plant 2-3 seeds per pot, and remember to mark each pot with a label.
Planting depth depends on seed type (check packet info), but a good rule of thumb is three times as deep as the seed is wide. It is better to plant seeds too shallow than to be too deep.
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.
Light Requirements for Growing Seeds
Bright light is essential for germination and strong seedling development. Place seed trays in a east or south-facing window. Supplement with a Soltech Aspect Growlight using a full-spectrum LED or fluorescent bulbs.
Seed Watering & Moisture
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.
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.
Germination can take several days or several weeks depending on the type of seed planted—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.
It is helpful to recognize the first set of leaves versus the “true” set of leaves—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.
Use G&B Organics All Purpose liquid fertilizer (3-2-3) diluted to ½ or ¼ strength. Feed seedlings weekly or every 10 days once seeds have germinated and grown their first set of true leaves.
Transplanting Seeds Outdoors
Wait until the seedling has formed at least two or three sets of true leaves before transplanting into a larger pot or outdoors into the garden. Reference seed packet or plant information for best time to plant outside. Check your soil temperature with a soil thermometer, and pay attention to nighttime temperature lows.
Slowly transition seedlings outdoors by placing 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.
We are proud to carry seeds from two excellent companies:
Territorial Seed Company
Territorial Seed Company is a family-owned business since 1979 from Cottage Grove, Oregon. They carry certified organic, biodynamic, and heirloom seed varieties. They have 44 acres of trial grounds at London Springs, south of Cottage Grove Lake. Each year, Territorial’s research garden staff grows and evaluates thousands of varieties for best taste, Northwest hardiness, and good germination.
Since 1995, Botanical Interests has been supplying gardeners with the highest quality 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 seed.