What to do this week: This is the busiest time in the garden. Put in perennials, woody plants, and frost-resistant annuals and vegetables such as lettuce, cabbage, peas, kale, and spinach. Seed root crops such as beets, radishes, and carrots. Thin them with scissors after they sprout. Sprinkle bulb fertilizer around but not on blooming bulbs. Spray tulip bulbs with repellent if you have critters, especially deer, or else give up on planting tulips. People love daffodils because nothing eats them. Hyacinths are more perennial.

Q. Do you have a recommendation for what to add to the soil to start the spring season? When I go to the garden centers, I don’t know whether I need manure, peat, bone meal . . .

JMD, Newton

A. There’s an old saying, “Feed the soil, not the plant.’’ Garden soil is a living environment full of billions of beneficial microorganisms that help your plants thrive in ways we only partly understand. I think well-aged manure (nicknamed “black gold’’) is perhaps the best food for living soil. It improves soil structure while feeding your plants, something synthetic fertilizers cannot do. Always buy aged manure. You can use it immediately, and it doesn’t smell. Since my garden is large, I sometimes get fresh free horse manure from a stable and age it myself in my compost pile for a year so it doesn’t burn roots or smell and contains fewer viable weed seeds. Horse, cow, and chicken manure are the most available types. Do not use manure from dogs, cats, or swine. Fish byproducts such as Neptune’s Harvest out of Gloucester are excellent, as is worm compost, called “castings.’’

Place manure between plants, not on them. I sometimes use aged manure to build a low, temporary earthen saucer around plants to direct rainwater to the roots without runoff. When adding plants, I combine manure in a wheelbarrow with the local soil I’ve dug up and use this mix around the roots in the holes, especially at the bottom. Apply aged manure to your vegetable patch at least 90 days prior to harvest, or better yet, add it to the soil at the end of the season after harvest for the following year.

Q. I have several oak trees, a crab apple, and some maples. Will they all benefit from caterpillar-control spray and, if so, how often?

S.K., (no community given)

A. Never spray an insecticide on a tree while it is flowering, or you will turn it into a killing zone for important pollinators. So don’t spray your crab apple in May while it is in bloom, said Abraham Monahan of Bartlett Tree Experts. He adds that bees are not attracted to maple trees when they flower or to oak trees. The end of April is the best time to spray for winter moths, which produce small green inchworms. You can spray for gypsy moths — dark, 3 inches long, and found mainly along the Interstate 95 corridor — in late May if you had them last year. If you had neither of these pests last year, do not spray this year; it’s not good for the environment, and trees can easily withstand a year of defoliation if you water them over the summer.

Event

Art in Bloom, the Museum of Fine Arts’ charmingly euphoric celebration of spring, runs April 29 to May 1 from 10 a.m. to 5 p.m. Volunteers from 50 New England garden clubs are assigned masterpieces to interpret with flowers. Bring the kids on Sunday, when there will be special activities for them. Visit www.MFA.org or call 617-267-9300 for more information about the event, which is free with museum admission. There are ticketed activities.

Send questions and comments — along with your name/initials and community — to stockergarden@gmail.com.