Annual Flowers: Starting Plants From Seeds

Annuals and biennials can be started indoors from seeds, sown directly in the garden, or purchased as transplants. If you start plants from seeds indoors, the seeds are usually sown eight to ten weeks before the last spring frost. If you raise your own transplants, be sure to harden them off by exposing them to outside conditions before planting in their intended site.

Annuals seeded in the garden sometimes fail to germinate properly because the soil surface crusts and prevents entry of water. One way to overcome this is to make a furrow in the soil about 1/2-inch deep and fill with vermiculite (if the soil is dry, water the furrow before filling with vermiculite). Then make a shallow furrow in the vermiculite and sow the seed at the rate recommended on the package. Cover the seeds with vermiculite and use a nozzle adjusted to a fine mist to water the seeded area thoroughly. Keep the seed bed well watered or cover with a mulch such as newspaper to prevent excessive evaporation and soil drying. Remove the mulch promptly after germination begins so young seedlings will receive adequate sunlight.

When most outdoor-seeded annuals develop their first pair of true leaves, they should be thinned to the recommended spacing. Excess seedlings can often be transplanted to another spot. This is especially true for seedlings growing in vermiculite-filled furrows. Zinnias are an exception to this rule of thinning. In many cultivars of zinnias, some flowers may appear with a large, nearly naked corolla and few colorful petals. This phenomenon is sometimes referred to as “Mexican hats.” To eliminate such plants, sow two or three seeds at each location, wait until the plants start flowering, and then remove plants with this undesirable characteristic. Thin the remaining plants to the recommended 8- to 12-inch spacing. Another exception is sweet alyssum, which is particularly susceptible to damping-off fungal disease. To insure a good stand of alyssum, sow seeds in hills.

Prepared by: Erv Evans, Consumer Horticulturist