A stevia plant takes about 90 days from planting to reach its first strong harvest. That is the short answer on stevia growing time, and it holds true for most home gardens. Set a young plant out in late spring and it fills out into a bushy clump by late summer. The leaves taste good all season, but they turn their sweetest once cool fall weather sets in.
The clock starts the day you plant, not the day you sow a seed. Seeds add weeks of waiting, and they fail often. When seeds do sprout, germination runs 7 to 21 days at around 70°F (21°C) with steady warmth and light. The tiny seeds need light to wake up, so press them onto the soil surface and do not bury them. Even then, many never come up at all. So the real stevia days to harvest depends a lot on how you start the plant in the first place.
Once the plant takes hold, growth speeds up fast. You can take a few light snips of leaves through summer for tea or a fresh taste. I always pinch the growing tips early, which pushes the plant to branch out and grow fuller. By the time it reaches full stevia maturity near the 90 day mark, you have a dense, leafy bush ready for a real cut.
Watch the plant, not just the calendar. The best moment to make your main cut is right as the first flower buds appear. Leaf sweetness peaks just before the plant blooms, then it drops once flowers open. The plant pours its energy into seeds at that stage, so the leaves lose some of their punch. Cut the whole plant back to about 6 inches (15 cm) above the ground when you see those buds. Leave that short stub and a few lower leaves in place. The plant will push out fresh growth for a second round before the cold arrives.
A few things speed the plant along or hold it back. Warm soil and full sun keep growth steady, and stevia loves a spot that gets six hours of sun or more each day. Cold snaps and soggy roots stall it, so wait until nights stay mild before you plant out. Feed it lightly and keep the soil moist but never wet. Push too hard with fertilizer and you get lush leaves with a weaker, more bitter taste, so go easy.
Cool weather is your friend here. The leaves build up the most sugar during the crisp days of early fall, before the first frost hits. That is the key to knowing when to harvest stevia for the strongest flavor. I've grown it in pots for years, and the late-season leaves always taste richer than the ones I pick in the heat of July.
Want a harvest much sooner? Start with a transplant instead of seed. A young plant from a nursery skips the slow, hit-or-miss germination and gives you a head start of several weeks. You set it out, give it warm soil and steady water, and you reach that 90 day harvest window without the gamble. I recommend this route to anyone trying stevia for the first time, since one weak seed tray can cost you the whole season. For most growers, a transplant is the simple path to a full, sweet plant in a single summer. Plant it in late spring, pinch it back as it grows, and make your main cut in cool fall for the best flavor.
Read the full article: Stevia Plant: Grow, Harvest, and Use It
