Starting Stevia from Seed

Seeds not planted within a few weeks should be stored in a rubber sealed glass jar placed in a cool, dark room or your refrigerator. Sow seeds indoors in early spring, or any time if you have a frost-free climate or plan to keep plants indoors. Transplants should be transferred to the garden at least two weeks after your last frost date. Plants will take at least 8-10 weeks to reach transplant size.
If you have developed a good seed starting method, go ahead and use it. In general, stevia should be treated similar to tomatoes when starting from seed. Here I describe my favorite method. I like to use individual cells or pots such as 6-pack plastic inserts. You will need a plastic flat or shallow container and a clear plastic dome or cover to go on top. Pots or cells should have drainage holes. Standard potting soil or seed starting mix works fine. If the soil is dry, moisten it slightly. Fill cells or pots level without compacting. Place 2-3 seeds on their sides in each cell or pot. Barely cover with fine horticultural vermiculite or a little potting soil.
Moisten thoroughly but gently with a spray bottle to settle the seeds and remove air pockets. Put a little water in the bottom of the flat to be absorbed from the bottom. That should be enough water until plants are up and growing. Place the clear cover on next. It’s fine if it doesn’t fit tightly. A little airflow is good. Put a thermometer under the cover. Place the container under a fluorescent light left on all the time and hung so the height can be adjusted. Keep the air temperature inside the plastic dome between 73˚ F. and 80˚ F. by adjusting the height of the light. A heat mat underneath could do the job as well, but the light itself improves stevia germination slightly.
In 6-12 days, tiny seedlings will begin to emerge. Take the clear cover off when more than half the pots or cells have seedlings showing. Don’t leave it on too long or the humid air will encourage damping off. At this point, leave the light on all the time at about five inches above the plants. Water from below. Pour about ¼ inch of water in the bottom of the flat for the pots or cells to soak up from below. Wait 4-6 days before watering again unless the soil dries out sooner. The goal is to keep the soil slightly moist, but not soggy. Avoid getting the leaves wet.
If the potting soil lacks any compost or fertilizer, Put a few drops of seaweed fertilizer or other weak, low nitrogen fertilizer in the water starting at about the third watering. Plants usually do fine without added fertilizer. When the seedlings are old enough to tell which one in each pot is strongest, cut the others off with a scissors. At about three weeks after sowing, begin to turn the light off at night. Maintain about 14 hours of light per 24-hour period. A timer is nice for this job.
At about 8-10 weeks from sowing, the plants may be transplanted or left to grow a few more weeks. Plants may also be kept as potted plants. A 4-6 inch pot is big enough for a small plant kept trimmed. Bigger pots work even better. Harden plants off for four to six days before transplanting to the garden, placing the plants outside in a protected area on nice days and bringing them in at night.

Pre-Sprouting Method

Transplanting tiny seedlings into their own pots or cells will maximize plant numbers, but this is time consuming and may damage some seedlings. Pre-sprouting is an alternative for maximizing plant numbers. It requires a plastic flat or similar shallow container with a clear plastic dome or lid, a thermometer, a spray bottle, and some biodegradable paper towels. Spread out a single paper towel and moisten with a spray bottle. Spread the seeds across half of the paper towel. Fold the towel in half over the seeds, then in half again. Lay the folded towel in the container along with a thermometer and put on the clear lid. Place under a fluorescent light left on all the time. Adjust the distance from the light so the temperature stays between 75°F. and 80°F. Turn the towel over once a day and spray a little water to keep it moist. In several days when the sprouts have green leaves, cut out a small section of towel where each sprout is located and place each one, green leafy side up, on top of the potting soil in it’s own cell or pot. fill in with a little vermiculite or potting soil so that just the tiny green leaves are showing. Keep moist and the little plants will take root and grow!

Copyright 2006 Jeffrey Goettemoeller