Caren White is a Master Gardener and instructor at Home Gardeners School. She has been associated with Rutgers Gardens for over a decade.
It used to be that if you wanted to add bok choy to your stir fry, you could only find it in specialty Asian markets. Nowadays, more and more gardeners are adding this cool season vegetable to their spring and fall crops.
What is Bok Choy?
Bok choy (Brassica rapa subsp. Chinensis) is a member of the brassica family. It is related to cabbage, but it doesn’t form a head like cabbage. It grows upright like celery. The flavor is a cross between cabbage and chard.
It is also known as Chinese cabbage because it is originally from China. The name “bok choy” means “white vegetable” because the base of the plants is white.
Bok choy is a biennial which is hardy in zones 4 – 7 but is grown as an annual. It is grown during the cool weather of spring and fall. The plants bolt in summer heat. They do best in partial shade, only requiring 3 to 5 hours of sunlight each day.
The leaves are bright green and grow upright. At maturity they reach a height of 1 – 2 feet with a spread of 1 – 1 ½ feet wide. The flowers, which are yellow, grow on stalks. The plants will bolt (develop flowers and seeds) when temperatures are consistently hot, but also if the temperatures are below freezing for a few days or if they plants are not watered and start to dry out.
Is Bok Choy Poisonous?
Bok choy contains glucosinolates which prevent the absorption of iodine in the body. Iodine is needed by the thyroid which produces hormones which regulate many critical functions of the body. Eating bok choy in small amounts will not harm you but if eaten in large quantities, it can be toxic.
How to Grow Bok Choy
In general, bok choy needs soil that is rich in organic matter with an ideal pH of 6.5 to 7.0. When preparing your garden, work in a good amount of compost and organic fertilizer. The plants are heavy feeders which means that they need a lot of nutrients. They need large amounts of nitrogen, potassium and phosphorus. Keep your garden well weeded so that weeds aren’t competing for the same nutrients as your plants.
If you are growing more than one row of bok choy, your rows should be 18 to 30 inches apart. Use row covers to keep pests such cabbage worms, flea beetles, aphids and other pests common to brassicas away from your plants.
Be sure to water your plants regularly. They will bolt if they start to dry out.
How to Start Bok Choy Seeds Outdoors
Direct sow your seeds in your garden one to two weeks after your last frost. Plant them ½ inch deep and 1 inch apart. The seeds will germinate within 7 to 10 days. Thin them to 6 to 10 inches apart when they are 4 inches tall. You can eat the thinnings in a salad.
Direct sow your seeds in your garden in late summer. For me in zone 6, that is August. Plant them ½ inch deep and 1 inch apart. The seeds will germinate in 7 to 10 days. Thin them to 6 to 10 inches apart when they are 4 inches tall. You can eat the thinnings in a salad. Apply a thick layer of mulch around your plants to help keep the soil cool and moist to prevent bolting in the heat of late summer/early fall.
How to Start Bok Choy Seeds Indoors
Start your seeds 1 to 2 weeks before your last frost. Plant them ½ inch deep in containers of premoistened soil. Germination should occur in 7 to 10 days. You can plant your seedlings outdoors after your last frost when the night time temperatures are consistently 50⁰F or above. Space them 6 inches apart.
Start your seeds indoors in late summer. For me in zone 6, that is August. Plant them ½ inch deep in containers of premoistened soil. Germination should occur in 7 to 10 days. You can transplant your seedlings outdoors 4 to 6 weeks before your last frost. Space them 6 inches apart. Apply a thick layer of mulch to keep the soil cool and moist to prevent bolting.
How to Harvest Bok Choy
Bok choy takes 45 days to reach maturity. You can start harvesting when your plants are 12 to 18 inches tall. You can either uproot the plants or using a sharp knife, cut the plants off 1 inch from the soil. Cutting them off above the soil encourages them to regrow for a second harvest. Another way that you can lengthen your harvest season is by succession planting in the spring. Plant seeds every two weeks until the weather warms, then resume planting mid-summer until late fall.
How to Store Bok Choy
You can store your harvest, unwashed, in a plastic bag for up to a week in the crisper drawer of your refrigerator. Do not wash until you are ready to use it.
© 2020 Caren White