For harvesting stevia, most obvious method is grazing in the Stevia patch. Pinch off a leaf when you think it’s ready and eat it. It’s comes even better when you combine it with a mint leaf. With a little more effort, you can use those fresh leaves and make a delicious tea with a tea ball or strainer just as you would do it with mint leaves.
Harvest time really rolls around when plants are fully grown. You’ll get the highest combination of leaf yield and glycoside content just before plants start blooming. When you see the first blossom buds forming, go ahead and harvest.
If you are growing Stevia as a perennial, you will want to leave about six inches of the plant to allow for re-growth. Otherwise, cut whole stems right off and tie into small bundles with a rubber band. Use a bent paper clip to hang these bundles upside down in a well ventilated location out of direct sun. Stretch some strings across the ceiling to hang them from if you need more hanging space.
The leaves will be nice and crispy in a few days, but still bright green. Strip the leaves off by hand and discard the stems, as they don’t taste as good. Store dry leaves in a clean glass jar with a good tight lid on top. Put the jar in a cabinet out of the sun. They’ll store for years that way. You can get some out to process further as needed.
Another drying method is to strip leaves from stems while still fresh and spread on a screen out of the sun or in a dehydrator on low heat (under 110 degrees F.) until crispy. Leaves are then ready to process or store away for later.