Bloom & doom in the biennial garden
As you probably learned in school, a biennial is a plant that lives longer than one year but less than two years. An ornamental gardener knows biennials as the garden flowers that seem to take forever to bloom — foxgloves, hollyhocks and Canterbury bells, among others.
A number of food crops are also biennials. They hold in the garden for a long time before blooming, but their blooms, unlike those of ornamentals, mean that the party is over. That’s because we want to eat the roots (carrots, beets, leeks, parsnips) or the leaves (kale, collards, parsley, chard, salsify). We are distressed when the plant flowers, because then the part we want to eat becomes hard or shriveled.
March is when biennial crops that have overwintered are likely to bloom. A flower stem will arise, buds appear, and soon flowers open. Flowering leeks have a tough stalk that subsumes the rest of the plant. Flowering carrots are shriveled and tough. Flowering chard has small, strongflavored leaves.
These plants do not come back. They flower, form seed and then die. So what’s a gardener to do? Two easy steps: Eat what you have grown before it flowers; and time your plantings to get the most to eat before the plant blooms.
Biennial crops evolved near the Mediterranean Sea. Their wild ancestors started to grow with the rains, then, after they were exposed to several weeks of cold — but above freezing — winter weather, they flowered. Our Bay Area Mediterranean climate allows us to see their full life cycle.
In the garden, if planting is timed right, you will be able to harvest your biennials for months. The carrots will hold in the ground; the chard will keep growing new leaves. In San Francisco, and other coastal, cool microclimates, we can plant biennials January through August. Inland, they can be started late winter and spring, then again in late summer or early fall, whenever the weather cools down. They should never be planted from mid-fall to the end of the year, since then they will not reach full size for harvest, yet are likely to bloom in spring and die anyway. (If you’re near the coast, be sure you put these crops in by August. If you’re inland, September or even early October can work. For exact timing, see the planting calendars in my book “Golden Gate Gardening.”)
If your biennial crops are blooming this March, there are two silver linings: One is that their flowers, except for those of beets and chard, attract beneficial creatures to your garden that will eat pest insects. So let a plant or two bloom to bring these helpers. The other is that the tender flowerbud stems of collards and kale are edible. Snap them off, a few inches down, before the buds open. Look the plants over carefully to find them all. The plant usually grows new stems of flower buds, allowing repeat harvests for several months. When the bud stems become too small or strong-flavored, pull out the plants.