Sow seeds outside 4/15-8/15 directly into garden soil seeds spaced 2” apart in rows spaced 18” apart. Keep seeds evenly moist until germination. Protect young seedlings from slugs by using Sluggo. Thin plants to 8” apart. Alternatively, start gai lan seeds indoors 4/1 at 77°. Days to germination: 5-8 days. Don’t let plants become potbound in their pots. Transplant outside 5/1, 8” apart. Gai lan plants needs consistent water throughout the growing season. Protect plants from deer, groundhogs, and rabbits which will devour them. Gai lan plants may be eaten by caterpillars. If they cause damage, hand remove caterpillars or spray organic BT.
Harvest when plants have plenty of leaves, reach 8-10” tall, and, if you want to eat the broccoli raab, have 2-3 flowers starting to open. Cut main stalk 2-3” above the soil. Plants will re-sprout.
Gai lan is Brassica oleracea and is insect pollinated and will cross-pollinate easily. Gai Lan will cross with any Brassica oleracea that are flowering at the same time (broccoli, collards, cabbage, brussels sprouts, kohlrabi, cauliflower). Isolation distance: ½ mile. It can suffer from inbreeding depression if you don’t save seeds from enough plants. Minimum population size: 10 plants. To harvest seed, allow plants to flower and collect seed from mature pods.