Temperatures spiked into the 70s during the weekend, just in time for the unofficial start of the vegetable gardening season. The week of St. Patrick’s Day has been written into the gardener’s mental calendar as the time for planting potatoes and onions, although they still can go into the ground during the coming month.

Onions, which are best planted from sets or starts in this climate, tend to do their best growing when the weather is cool. The flavor of onions is tied to two things: adequate water while they’re in the ground and plenty of growing time during the cooler part of the season. Onions planted early in the gardening season are the sweetest.

Similarly, potatoes thrive when they can produce their plants and set their tubers before the summer’s heat arrives. Even if potato vines are nipped by frost, they’ll usually bounce right back.

When planting potatoes, use either seed potatoes from a gardening store or organic potatoes from the supermarket. Conventional grocery store potatoes often are treated with a growth retardant to inhibit sprouting. This is hard to believe when they start growing in your pantry, but it’s true. If you want to plant potatoes that will reproduce other potatoes, steer clear of treated spuds.

Planting herbs

This also is a good time to start thinking about starting culinary herbs. Both annual and perennial herb seeds can be planted during the next six weeks. As the weather warms, most herbs can be direct-seeded into the bed, although you may want to transplant them from starts that you seed indoors now.

The one herb that really doesn’t grow well from seed is rosemary, which has a very low germination rate, owing largely to the fact that its seeds take weeks to sprout. Rosemary is best planted from rooted cuttings.

Perennial herbs, such as sage, tarragon, thyme and oregano, generally take longer to germinate, and I tend to start new plants indoors and move them outside once overnight temperatures stay in the upper 50s. However, oregano and some varieties of thyme can be directly planted into the ground. They tend to reseed themselves, anyway. I’m thinking particularly of oregano, which sometimes behaves like mint in its growing habit and can even become invasive.

Annual herbs will be testier in cool weather and should be started indoors and transplanted if you want to be using them by Memorial Day. However, the seeds of annuals generally don’t take as long to germinate and can be sown directly. Dill is a good example here. To establish a dill bed, all you have to do is sprinkle seed on the ground.

Same thing holds true for cilantro. Its seeds have a harder shell and should be planted into soil that will remain moist, but it will reseed itself throughout the growing season. Unfortunately, coriander seed packaged as a spice often is treated and can’t be used to start cilantro. You’ll need to use cilantro seed.

Parsley is supposed to be an annual in this climate but I have had some varieties of parsley return year after year. It’s definitely one that can be planted early and started indoors or out.

Marjoram and basil are true annuals and should be started indoors and transplanted after the danger of frost has passed. In this climate that will be in late April. Because basil will bolt fairly quickly, the gardener who wants to have a continuous supply will want to start several plantings, a couple of weeks apart, from now through May. Once basil flowers, the flavor of the leaves can turn bitter. For that reason, it’s nice to have a later planting to use when your first round of basil goes to seed.

However, basil is a good example of why starting your own herbs from seeds can expand your harvest. Most greenhouses offer starts labeled as sweet or Italian basil, but basil comes in many varieties and the more exotic generally must be started from seed. For example, Mexican and lemon basil bring a different dimension to cooking. These varieties, as well as the Persian basils, which do service as aromatics and aren’t generally used in the kitchen, can be hard to find in local greenhouses.