Chinese cabbage refers to two different cool weather crops that lend themselves to Bay Area fall and winter gardens.
Chinese cabbages (Brassica rapa) are variations on the lowly turnip. The two subspecies we most commonly see are forms of Napa cabbage (var. pekinesis) and bok choy (var. chinensis). These healthful foods have been grown in China since before the 15th century.
Also known as Korean small cabbage or celery cabbage, Napa cabbage has a milder flavor than more domestic varieties, but it packs a nutritional punch that’s difficult to beat. According to a study conducted by the Centers for Disease Control in 2014, Chinese cabbage ranks second only to watercress as a nutrient dense food. Napa cabbages come in both head and loose leaf varieties. Napa cabbages can be planted in the Bay Area twice each year: first, February through April; and again, August through October.
Unlike the Napa cabbages, bok choy does not form heads. Bright white stalks give way to dark green blades, growing in a cluster, much like celery. Bok choy can be planted in the Bay Area in September and October, and then again, February through April.
How to grow Chinese cabbages
These biennial plants are generally grown as annuals. If you allow your plants to go to seed, you can create a seasonally perpetual crop within your landscape. To begin, find a location with full or partial sun and well-drained soil. Adding aged compost to the planting bed ahead of time can provide a nutritional boost to your plants and improve soil quality, while you’re at it. Chinese cabbages can also be grown in containers. Use pots that are 8 to 12 inches across and 18 to 24 inches deep. Seeds should be planted 1/2 inch deep and successful seedlings should be thinned to 12 - 18 inches apart. These plants do not transplant well, so it is better to put them where you want them right from the beginning.
Pests and diseases
Being closely related to broccoli and cauliflower, Chinese cabbage is subject to many of the the same pests: aphids, flea beetles, armyworms, loopers, cabbageworms, leaf miners, and millipedes. Common diseases include white rust, damping-off, yellow virus, clubroot, black rot, and bottom rot. Many of these diseases can be prevented by allowing soil to dry out between waterings.
Harvesting Chinese cabbages
Chinese cabbages are good candidates for succession planting. If you start one new plant per person every two weeks, through fall and winter, you will have an abundance to harvest. You can extend that harvest by only cutting away outer leaves on an as-you-need-them basis. These plants will continue to produce inner leaves through the growing season.
Like other cabbages, these plants to not produce a lot of ethylene gas. Ethylene gas is what makes fruits and vegetables ripen. Cabbages are, however, very sensitive to the ethylene gas produced by other plants, so it is a good idea to keep harvested leaves or heads in a plastic bag in the refrigerator. Or, your can always try your hand at fermenting some cabbage for your very own kimchi!
Cole slaw and corned beef simply wouldn’t be the same without cabbage.
Cole crops, or cruciferous vegetables, such as broccoli, cauliflower, Brussels sprouts, and the lowly cabbage were placed in the same family partly because they all have four-petaled flowers that look like a cross (Cruciferae is Latin for “cross bearing”). Luckily for us, there is no cross to bear when it comes to growing cabbages!
These densely headed members of the Brassica family are biennials grown as annuals. If you grow cabbage for seed, you will want to make sure there is some distance between your cabbage plants and other members of the Brassica family because cross-pollination can occur. Seriously! In fact, that’s how rutabagas came to be - cabbages crossed with turnips! Hmm, how about tiny cauliflowers that grow on a stalk, like Brussels sprouts - we could be on to something!
How cabbage grows
In the wild, as temperatures reach 80°F, two-year old cabbage heads send up a flowering stalk, the same way lettuce and spinach do, in a process called bolting. Tiny helicoptered seeds catch rides on every breeze, spinning their way to new homes. Over the next year, a taproot will go down and a head will form, preparing to repeat the cycle.
How to grow cabbage
Cabbage seeds should be planted 1/2 inch deep, with plenty of space around each plant. Cabbage plants can reach 2 feet in diameter. The more space they are given, the faster they will mature and the less likely they are to being attacked by pests or disease. Cabbage plants prefer sunny locations with good drainage, but they can tolerate partial shade. Cabbage grows best when given occasional deep waterings, rather than frequent shallow irrigation. Also, you can prevent many diseases by avoiding overhead watering. Cabbage is a heavy feeder, so you may want to work some aged compost into the soil before planting. In spite of having a taproot, cabbages can be grown in containers that are at least 8 inches deep. Rather than have all your cabbages reach harvestable size on the same day, it’s a good idea to plant seeds in succession.
Cabbage pests & diseases
There are plenty of pests and diseases that attack cabbage. The nice thing is, cabbage grows a set of outer leaves that frame a tightly packed head. Most cabbage pests never reach the side of the head. That being said, it’s a good idea to know what you’re up against. Cabbageworms are the most common cabbage pest in San Jose. These small white imported moths have black dots on their wings and they are relentless. Eggs are laid on the underside of leaves. Larvae emerge and start feeding like crazy. You can hand pick the caterpillars and I have taught my dogs to chase the moths away.
Row covers can also protect your plants from cabbageworms. Cutworms, aphids, armyworms, cabbage maggots, darkling beetles, earwigs, flea beetles, wireworms, whiteflies, leaf miners, nematodes, and the ever-popular slugs and snails will appreciate finding cabbage in your landscape, but good cultural care and regular monitoring can minimize the damage. Cabbage is prone to several diseases, including clubroot, damping off, downy mildews, black rot, yellow virus, Verticillium wilt, Phytophtora root rot, and bacterial leafspot.
Don't let all those threats deter you from trying your hand at growing cabbage. If you buy cabbage in the store, chances are 30 to 1 that it was grown in China. This is unfortunate, because cabbage is easy to grow, it looks nice in a landscape, and all that shipping traffic can’t be good for the environment. Grab a pack of seeds, or a couple of seedlings from your local garden store, and give cabbage a try.
Peasants and Senators have been growing cabbage for nearly 3,000 years. You can do it, too!
Erratically flying white butterflies that look more like moths and favor members of the cabbage family are insidious garden pests. If that weren't bad enough, chemicals found in their favorite foods make them distasteful to birds.
Cabbageworms start out as tiny yellow, green, or white, rocket-shaped eggs that are laid singly on the undersides of leaves. If you have a hand lens, you can see distinct ridges on the eggs. Whether you can see that well or not, do your plants a favor and extermigate the eggs whenever you see them.
Cabbageworm butterflies tend to be white or off-white with one to four black spots on the wings. Larvae are green and fuzzy and can grow to one inch long. Larvae often have a faint yellow stripe on the back and broken yellow lines along the sides. Pupae are a mottled brownish grey. The chrysalis matches the leaves and is often found along the midvein.
There are actually several different white butterflies that lay eggs on plants in the cabbage family. Collectively, they are called ‘cabbage whites’. Native species of cabbage whites include:
The imported cabbageworm, Pieris rapae, has largely replaced these native cabbage butterflies.
Damage caused by imported cabbageworm
As soon as the eggs hatch, fuzzy green caterpillars start feeding, and feed they do! They start by eating their own eggshell and then they chew round holes in leaves at an alarming rate. Healthy plants can look tattered in only a few days. Leaving trails of brown fecal pellets on leaf surfaces, larvae may also burrow into cauliflower and broccoli heads, making them inedible.
The first sign of cabbageworm infestation is random, round holes in the leaves of cabbage, kale, cauliflower, broccoli and other members of the Cruciferae or cabbage family. You may also notice greenish brown fecal pellets littering leaf surfaces.
Since cabbageworms are active year round in California, the damage they cause can be extensive. A single adult cabbageworm can fly over 7 miles in a single day, so you really need to be on the alert.
How to control imported cabbageworms
Unlike many other invasive pests, imported cabbageworms actually have some enemies already. Tachinid flies and a handful of parasites feed regularly on cabbageworm eggs and larvae. Speaking from experience, I can tell you that those natural controls will not be enough once cabbageworms have found your crops. You can spray Bacillus thuringiensis (Bt) or spinosad for a measure of organically acceptable control. Handpicking larvae and extermigating eggs really are really your best control measures. And get rid of any nearby weeds from the cabbage family. Adult cabbageworm butterflies feed on nectar from flowers, preferring blooms of purple, blue, and yellow.
Personally, in addition to regularly monitoring plants for the presence of cabbageworms, I have trained my dog to chase cabbage butterflies out of my yard. It helps, and it's pretty fun to watch.
You can grow a surprising amount of food in your own yard. Ask me how!