Growing Plants From Seeds
by Cecile Garrison, UC Master Gardener

Even though the ground is still too wet and it's too cold to garden outside, now is a good time to start our spring and summer gardens by planting seeds inside! We don't have to wait for the summer annuals to show up at the nurseries. We can start almost any annual, biennial, or perennial that thrives in our climate from seeds and end up with more plants for less money.

Starting seeds indoors is fun and easy as long as the temperature, light and moisture are right. It doesn't require a lot of money or elaborate equipment. I try to choose plants and varieties that are not typically found in the nurseries. For example, I started the ‘Purple Wave' petunia from seeds several years ago before they became available locally. I have also started lavatera, an easy to grow perennial in constant bloom with hollyhock-like flowers. Bee balm (Monarda sp.), nicotiana, phlox, and cup-and-saucer vine (Cobaea sandens) are a few of my favorites to start from seed.

A great plant for kids of all ages to grow from seeds is the ornamental gourd. Their vine growth is visible daily! Gourds need a fence, trellis, or teepee like structure to grow on but require very little ground area. I grow them in an eight-inch by forty-foot strip of ground between the driveway and fence in full sun.

I start plants from December through February with a ground-planting goal of the first week in April. Some seedlings outgrow their containers fast and require repotting into larger containers before they are transplanted into the garden. This is especially true of tomatoes. I usually repot them two or three times before they make it to the ground in April, but you could plant them in mid-March after the danger of frost.

Seed containers must have drainage holes and be at least two inches deep. Containers can be peat pots, clay pots, milk or egg cartons or seed planting trays with lids, which are found at most garden centers. Use a fresh seed starting mix for your potting soil and be sure to pre-moisten the mix before you fill and level your container. It's extremely difficult and a lot messier to moisten the mix after you put it in the trays.

Check the seed packet for recommended planting depth. Some seeds need light to germinate and should be left uncovered. The usual rule is to bury the seed as deep as its width. Don't forget to label your seeds! They will all look alike when they germinate.

To help maintain moisture and prevent the potting soil from drying out, I cover my newly planted seed containers with a clear plastic dome, plastic bag, or plastic wrap. Seed germination occurs readily when the soil temperature is about 75 degrees. Try setting seedling trays on a heating pad or electric blanket and be amazed at how rapid and uniform germination is.

When you see the leaves of the emerging seedlings, it is time to remove the plastic cover. Growth is best when the air temperature is between 65 to 70 degrees. Water the seed trays from the bottom or mist the seedlings from the top.

Bright light is critical for getting strong, vigorous seedlings. Hang a shop light with ordinary fluorescent bulbs two to three inches above the plants. Or purchase special light bulbs for growing plants indoors. They need this light at least twelve hours a day.

When seedlings have two sets of leaves they can be repotted into a larger container. I use four-inch peat pots, which I later put directly into the garden to avoid transplant shock. Lift transplants by their leaves, not by their fragile stems. Replant them in the larger container in moist, all-purpose potting soil at about the same depth they were before. Seedlings should be kept evenly moist but not soggy.

Plant tender annuals in the ground when the soil is warm. When transplanted too early, they don't grow, they just sit there, plus they are very susceptible to a late frost. So, don't be impatient with your tender, new plants. Gradually acclimate your seedlings to outdoor weather by setting the seedling pots in a semi-shady, protected location for an hour or two the first day. Extend the time until eventually the seedlings spend all day outside. This is called ‘hardening off', a common practice in commercial nurseries.

If your seedlings are weak and skinny, they probably are not getting enough light. If they suddenly wilt and die, they probably have a fungal disease called damping-off. To prevent damping-off, use clean containers and fresh potting (not natural soil) mix, and keep the mix evenly moist but not saturated.

That's really all there is to it. Now, go buy some penstemon, scabiosa, heliotrope, or ornamental gourd seeds and have fun growing something unusual, interesting, and pretty.

January 24, 2002