Kohlrabi
How to grow Greens
For all greens, nitrogen is a necessity - the more nitrogen that is available, the bushier and leafier your greens will be. Prepare your soil with a nitrogen boost before planting, then side dress with nitrogen throughout your growing season to maintain leaves.
Also, temperature is a key factor with greens. Most can withstand light
freezes, especially when covered with a plant-protector fleece. However, temperatures above 75oF will usually cause most greens to bolt (begin flowering to produce seeds, ie, the end of their season) - it’s important to understand your area’s temperatures in order to decide if fall or spring growing is better for your greens: in southern climates with hot summers and mild winters, fall is the best growing season, while in northern climates with longer springs and harsher winters, early spring planting gives the best production. If you’re unsure, you can always start your greens in the fall and cover them as needed. A hard freeze can kill your greens, but light freezes will often make the leaves taste crisper.
Pests are similar on most greens as well. Cabbage loopers and other types of caterpillars are drawn to leafy greens, but as they are mostly grown in cooler weather, pests are often a sign that it is too warm and the plant will bolt soon. Flea beetles, cucumber beetles, harlequin bugs, and aphids can be prevalent in greens, so always be sure to wash your greens before eating. Because greens are directly edible, take care with any pesticide use and be sure it is marked for vegetable gardening on the label.
If growing microgreens, these are often best done indoors, in controlled environments. Add sterilized potting soil (to prevent fungus and gnats) to a propagation tray, or use seed mats. Liquid fertilizer is best for this use, but isn’t a requirement. With microgreens, spacing isn’t really an issue, because your seedlings will be used when small. Microgreens do need to be kept moist, but too much moisture can promote mold. Harvest when your microgreens are of a usable size. Use scissors to cut the tops, leaving the roots intact and leave a few lower leaves if you want them to regrow.
Kohlrabi
Kohlrabi is a brassica, like cabbage, broccoli, or cauliflower. Purple varieties tend to be more insect resistant. Kohlrabi should be planted in full sun, close to other roots, like potatoes, beets, onions, and away from pole beans, tomatoes, and strawberries. Kohlrabi are big drinkers and feeders, which means they'll need a good amount of water and fertile soil. Kohlrabi does better in acidic soil with good drainage. Because kohlrabi is a “root” vegetable, it is usually better to plant them directly in your garden, but like cabbage, they need temperatures
around 65oF to germinate. If starting them indoors, transplant the same way you
would cabbage. Weed carefully and often, as kohlrabi can be choked by weeds
early on. Wait until the seedlings are about 6” tall to thin. Space them 8” apart
and add compost. You’ll want to have compost all around, but especially at the
base of the seedlings to help support the above ground bulb. Kohlrabi need lots
of water, but keep the watering to the base to decrease the possibility of rot. If
your plants are not kept well watered, the bulbs can become woody.
To help with some pest and disease problems, you can make a barrier around
your small plants. Cardboard or foil is a good barrier, and needs to be buried into
the top inch of soil. This is really only needed for when the seedlings are under
6-8”. After the plants are larger, you can “collar” or tie up the leaves to keep them
up off the ground and prevent more pests and rot. If any plants do show signs of
rot or other diseases, remove the entire plant to prevent spread.
Kohlrabi are ready to harvest when they are of a usable size, usually that of a
tennis ball (2-3”), which is between 45-60 days. You will pull the entire plant up
for harvest. You can cook or eat kohlrabi raw. The entire stalk, leaves, and globe
are all edible!