How to Start Begonia Seeds

By Andrea Di Salvo, eHow Contributor

These tender perennials are familiar to most gardeners in the U.S., most of whom grow begonias as annuals because the plants can't abide frost. Despite the begonia's fragility, though, gardeners still love these flowers because they are both forgiving and easy to grow. If conditions allow, you can start begonias in a cold frame, an outdoor nursery or indoors under natural or artificial light. With just a little bit of preparation, these blooms will grace your garden or flowerbed all summer long.

Things You'll Need

• Begonia seeds Coarse sphagnum moss, gravel or pebbles Pasteurized soil Sand Peat moss Flats Glass or plastic coverings Suitable garden area or containers

Instructions

1. • 1
     Plan in advance. Allow anywhere from 10 weeks to 6 months to grow begonias from seed. Seeds sown in February or later probably won't flower well that same year, so start seeds between October and December for 4-inch plants the following spring.
   • 2
     Ensure drainage. Improve drainage by placing a layer of coarse sphagnum moss on the bottom of the flat before adding the potting mix. If growing in pots, use gravel or pebbles from a freshwater stream.
   • 3
     Mix soil. Prepare a finely textured planting mix by combining equal parts pasteurized soil, sand and peat moss. Press the blend through a sieve to create a fine texture.
   • 4
     Plant into flats. Scatter seeds on the surface of your potting media. Press in lightly but leave uncovered so light can reach the seeds.
   • 5
     Keep moist. Cover the flat with glass or plastic to maintain high humidity. Water from below, by placing the flat in a tub of water, to avoid damping-off.
   • 6
     Maintain temperature. Germinate at 68 to 72 degrees F with nights no colder than 55 degrees. Seedlings usually will emerge in 7 to 15 days with a soil temperature of 70 to 80 degrees.
   • 7
     Harden off. Harden the begonias for transplant by placing them outside for a short time each day. Avoid placing them in direct sunlight, since the leaves sunburn easily.
   • 8
     Prepare soil for containers. Prepare a garden space or container with moist but well-drained soil that is rich in organic matter and has a pH of 6 to 8. Make sure the area is in dappled sunlight or part shade with a northern or eastern exposure.
   • 9
     Plant out. Transplant the begonias 30 to 45 days after sowing, once all danger of frost has passed and nighttime temperatures no longer drop below 50 degrees F. Begonias prefer 65-degree nights and 75- to 85-degree days.

     
     

     Tips & Warnings

     • Begonia seeds are very fine, almost powder-like, and need light to germinate. Expect 70 percent germination from seed from the previous summer's crop. Older seed will germinate at roughly 50 percent to 60 percent. Even perennial begonias will not winter in most parts of the U.S., but begonia grandis is hardy in zones 7 and 8, and in southern areas of zone 6.
     • Feed begonias sparingly, because over-fertilizing can cause weak stems that need staking. A single application of compost or fertilizer should serve your plants all season.