Every summer I get numerous emails asking just when the plants are ready to harvest. These requests usually contain some pictures of the plants, and often my responses are just as much about when to harvest as they are about the health of the plants. These are interrelated issues, so my first post will be on when to harvest and my second will be on healthy plants.
The ideal time to harvest is when your plants have set large, healthy leaves and the stems are still standing (mostly) upright. Plants will be about thigh-high and most (if not all) of the leaves on the stem will still be green. At this stage it’s still easy to gather one planting/bunch of plants with one arm and cut them easily with the other hand. (For cutting by hand I recommend a saw-tooth sickle like this one from Hida Tool.)
If you let the plants grow too much, the stems become too thick and too tall. Both of these make cutting difficult: thickness because you’re forced to cut fewer stems at a time, and height because the stems weave themselves into the rows on either side and you end up exerting a lot of energy to get the ones you’re cutting separated. Also, the taller the stems grow, the more they block light from reaching the base of the plants, and the sunlight-deprived leaves lose their indigo content, turn yellow, and die. (More on this is my next post!)