A few years ago I began converting a portion of my cabbage harvest into stinky but mouthwatering kimchi.
Cravings for kimchi led to last year’s troubled experiment with growing Napa cabbage – the traditional cabbage for making kimchi. Also known as Chinese cabbage (brassica rapa, Pekinensis Group), Napa is said to have more nutrients than other cabbage varieties.
I am a sucker for colorful, unusually-shaped vegetables so I bought seed for Scarlette Chinese Cabbage, a showy variety with bright magenta leaves, a pale yellow base, and contrasting white midribs. The catalog said these cabbages could bolt if exposed to temperature fluctuations as young seedlings but I didn’t expect that to affect my plants.
The Scarlette Chinese cabbage seedlings were relentless. They crowded out other cabbage varieties in my seed flats and grew incredibly fast once transplanted into raised beds. They were a beautiful addition to the garden but quickly bolted. I salvaged a few loose heads for meals but mostly harvested cabbage greens. These became dehydrated vegetable flakes for an upcoming Arctic camping trip.
Why did they bolt? Why would any self-respecting cabbage bolt?
The typical culprit for bolting vegetables in a well-maintained Alaska garden is the short nights of our growing season. Night duration impacts many plants through a phenomenon called photoperiodism, by which plants use their photoreceptors to measure the amount of light they receive. “Long day” plants like barley, spinach, radishes, and cilantro start flowering when nights are shorter. Short day plants like sunflowers need longer nights to start flowering.
Nurseries often use photoperiodism to trick plants into blooming but it seems to be less common for home gardeners to trick plants into not blooming. It’s easier to avoid plants that bolt or look for bolt-resistant cultivars. Perhaps that’s why photoperiodism is barely discussed in any of my gardening books.
All this aside, cabbages are usually categorized as “day neutral” plants, meaning they disregard day/night length. If they are bolting early in the season, it probably has nothing to do with photoperiodism.
Another culprit for bolting that might be relevant to my Chinese cabbage is called vernalization.
Vernalization is a beautiful word that describes how a period of cold weather is necessary for the flowering of many plants. It is more likely my Chinese cabbages bolted due to a cold spell in spring when I took my seedlings outdoors.
Other factors for bolting that are important to consider if day neutral plants are bolting include the soil quality, moisture level, and any other factor that might cause plant stress.
Chinese cabbage is a cool-weather crop that clearly wants to do well in my garden and I haven’t given up on it yet. This year I’ll wait to put seedlings outdoors until later in the spring when we aren’t as likely to have cold snaps.
Maybe I’ll make some scarlet kimchi after all.
Additional resources: I found a few good online resources for gardeners on photoperiodism, including a blog post from High Mowing Organic Seeds and an article from the Oregon State University Extension Service. Interesting scientific tidbits about photoperiodism and vernalization are shared in the book What a Plant Knows: A Field Guide to the Senses by Daniel Chamovitz.