Despite the slow start to spring (as snow flurries Friday morning reminded me), this is a good week to start seeds indoors for early crops and for plants that take the whole growing season to mature.
I used to start leeks in mid-February, but now wait until the first week of March and find they grow just as big as always. And starting later means less time spent babysitting seedlings. While onions grown from sets mature around mid-July, earlier than onions from seed, growing onions from seed allows you to try many more varieties than are sold as sets. The downside is that seedling onions take most of the summer to reach maturity. You can grow your own sets, however, which gives you the wide choice of varieties along with the earlier harvest, which allows you to plant another crop after the onions. Choose storage varieties for onion sets and sow seeds thickly enough to keep the crowded bulbs very small. You can grow a lot of sets in 1-2 square feet. I sow mine directly in the garden in the last week of May, at a rate of 2-3 seeds per square inch. I don’t add compost or other nutrients before planting because I want tiny little sets, smaller than a dime. The smaller the onion sets are, the earlier you can plant them next spring. It doesn’t seem logical, but to make a long story [somewhat] shorter: the larger the onion sets are, the more likely it is that a cool spell will vernalize them, meaning make them produce flower stalks rather than bulbs. Planting large diameter sets (larger than a nickel) later in the spring reduces the chance of flowering because cool weather is less likely–but then the plants don’t have as much time to grow roots before the long days of June stimulate bulb formation. Which means smaller onions at harvest time.
After that onion detour, back to starting other seeds indoors: Sow tomatoes, peppers and eggplant now, if you haven’t already done so. Celery and celeriac seeds should be started now, because the seeds are minute and seedlings take a long time to grow to a good size. If you want an early crop of cabbage and cauliflower, start a few plants now and plan to start more next month for later harvests. If you don’t have leafy greens overwintering in the garden and are in a hurry for something green, sow some of those indoors. For such early plantings, stick to annuals, such as lettuce, spinach, Chinese cabbage, leaf radish, leaf mustard and other annuals. You can try biennials, such as Swiss chard, collards, endives, and they might be just fine, but it depends on the spring weather. If there is a late cold spell in April it can cause them to flower this summer instead of next year as they should (again, see the vernalization info mentioned above). If you have overwintered chard, spinach, kale, lettuce and other greens in the garden there is no need to plant early seedlings—the old plants have big roots and leaf growth will be rapid as the weather warms.
Starting seeds indoors requires bright conditions for the seedlings, such as under grow lights, in a south-facing sunroom or bay window. There is rarely enough sunlight to grow them on a windowsill. If they don’t have enough light, seedlings grow long stems and lean toward the light. To make up for less-than-perfect indoor light, put the seedling trays outdoors in a cold frame or unheated greenhouse whenever there is sunshine. Take care to open the cold frame or greenhouse vents enough to keep temperatures from getting much above 21oC (70oF). It won’t be much longer before you can also set seed trays outdoors for a few hours on warm, sunny days (continue to bring them in at night as it will be too cold for them).
Early Zucchini: Fans of the earliest possible zucchini should start seeds by mid-March for really early plants. This only works if you have a sunroom or greenhouse where you can keep the large, rapidly growing plants until you set them out around May 1st. For such early plantings I grow the parthenocarpic variety ‘Partenon’ from William Dam Seeds because the flowers don’t have to be pollinated for the fruit to develop (Salt Spring gardeners will be able to buy this variety from the Chorus Frog Farm stand this spring).
Spring Pests: It is the time of year to remind you to control climbing cutworms: these big fat caterpillars have been in the garden all winter and continue to eat ragged holes in leaves of vegetables until the end of April. After that they transform into pupae (those mahogany coloured “bullets” you see in the soil in May and June) and later in the summer the moths emerge from the pupae. The cutworms hide during the day, but come out to eat leaves at night. It is not hard to find them on leaves by the light of a flashlight just after dark. For photos of this insect check this.
Slugs are active and laying eggs now so you might want to start using iron/ferric phosphate slug bait to control them around garden beds that will planted next month. Some of these products are certified for organic growers (e.g., Sluggo). It works best to sprinkle small amounts of the bait over the soil in an empty bed, replacing it every week or two. Because the bait attracts slugs, don’t encircle the plants you are trying to protect with a ring of bait. The iron takes a couple of days to work, which gives slug time to eat the bait and your plants before they are affected.