Temperatures guide best times to sow seeds

With this latest round of snow and ice, the last thing on most people’s minds is planting a garden. Although the soil is frozen solid, now is the time to begin thinking about what to plant. Even though garden centers and hardware stores are advertising seeds and seed-starting kits, the early bird may not necessarily get the worm. Here is what you need to know about timing the planting of your garden this spring.

Knowing when to sow garden seeds may mean the difference between a bountiful harvest and a lackluster weed patch. Many vegetables will germinate and grow in cool soil temperatures. For example, peas will start growing when the soil is 40 degrees.

Although lettuce, parsnips and spinach can sprout at temperatures below 40 degrees, they do their best when the soil warms to 45 degrees.

However, warm-season crops such as tomatoes, sweet corn and beans prefer soil temperatures of at least 55 degrees for seeding and transplanting. Peppers, cucumbers, melons and sweet potatoes need it even warmer at 60 degrees.

One of the most neglected tools for gardeners is a soil thermometer. Soil temperature is a much better indicator of when to plant seeds or set out transplants than air temperature and calendar dates. Planting when the soil is too cool can result in rotted seeds and transplants that just don’t grow.

Taking soil temperature accurately is a bit of a science. Use a metal soil thermometer found at many retail outlets. Measure 2.5 inches deep between 10 a.m. and 11 a.m. Wait to plant until you have measured consistent temperatures for at least four or five days in a row.

Here is a brief list of minimum soil temperatures for many of the common vegetables grown in local gardens.

¢ 35 degrees: lettuce, onion, spinach

¢ 40 degrees: beet, cabbage, carrot, cauliflower, parsley, pea, radish, turnip

¢ 50 degrees: asparagus, corn, tomato

¢ 60 degrees: bean, cucumber, eggplant, muskmelon, okra, pepper, pumpkin, sweet potatoes, squash, watermelon.