It’s getting cold here in the
to bring in the stevia plants before our first hard freeze. As far north as
USDA plant hardiness zone 8, stevia plants can usually survive winter in the
field. The tops might die back, but the roots can survive as long as the ground
does not freeze. Mulch can help prevent frozen ground.
I harvested my stevia plants more than a month ago, in September, leaving stubs of 4 to 5 inches in length. The plants have sprouted back somewhat, and we’ve had some frosts at night. That’s OK, because stevia tops can withstand a few degrees below freezing in the fall. Even if the tops are damaged, the roots can survive. But the soil will eventually freeze here. Therefore I dug a few plants for overwintering on this late October day. I square plastic used pots that are 4 inches in diameter and several inches deep. The pots should have drainage holes. If a plant is too big, the crown may be divided into two plants. A standard potting mix for houseplants will work just fine, usually including peat and vermiculite or perlite. You can even mix in a small percentage of garden soil.
The plants might survive in a sunny window. They will not grow much because of the short winter day lengths, but the roots will probably survive anyway, and sprout back when days grow longer in the spring. I prefer to keep my plants under a fluorescent shop light left on about 15 hours per day. A timer is helpful. Stevia plants thrive with the longer light period. Short days trigger more blossoming and less leaf growth. Blossoming is more stressful for the plants already weakened from being transplanted. Keep the soil moist as you would for any houseplant. Added fertilizer will probably not be needed. Slow growth is best. Stems may be harvested when they get long and lanky.
It’s also possible to overwinter stevia roots by packing them in moist soil or peat moss and placing them in a basement or root cellar where it stays cool, but not below freezing. The survival rate may not be as high, but it is less work. The roots will remain more or less dormant until you dig them up in the spring.
Do you have a stevia question? Email Jeff at firstname.lastname@example.org and I might answer it in a future edition of this newsletter.
The Stevia Grower Newsletter is written by Jeffrey Goettemoeller for Prairie Oak Publishing. Jeffrey is an author, publisher, and horticulturalist. He sells stevia books and seeds at www.growingstevia.com.