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Ask the Gardener: Is it safe to add mulch around vegetable plants?

Ask the Expert
Zinnias-in-Bloom
It's not too late to plant zinnias -- and rabbits won't eat them. Shutterstock

What to do this week: Plant heat-loving tomatoes, corn, eggplants, peppers, melons, okra, squash, pumpkin, and cucumber. Plant bean seeds 2 inches deep every two weeks for a continuous harvest. Keep planting annual flowers. Rabbits don’t like impatiens, snapdragons, nicotiana, marigolds, or zinnias. Plant tender summer tubers such as dahlias, begonias, gladioli, and caladiums. Dig up, divide, and move perennials as well as shrubs or trees now to take advantage of June rains. This is the last week to pinch back your chrysanthemums, cut back your New England asters by half, and thin your phlox by cutting out half the stalks to get more flowers and less mildew.

Snapdragons-in-Bloom
Snapdragons add rich perfume to the summer garden. —Goldsmith Seeds/Associated Press/File

Q. The amount of direct light hitting the various garden beds of my condo courtyard changes constantly throughout the day. How can I tell which are the sunniest areas without sitting out there all day with a logbook?

C.T., Salem

A. Buy some young sun-loving annuals such as zinnias this week and plant them in different spots in your garden. Those that perform best will signal that they are growing in the sunniest spots. It’s also not too late to sow annual flower seeds such as nigella, marigold, and gomphrena, which saves money and gives you more choices than starts. “The Flower Garden: How to Grow Flowers from Seed’’ by Clare Foster and Sabina Rüber, is a new book with step-by-step instructions on how to sow and grow some of the quickest and easiest annuals for cutting or for beefing up a tired flower garden.

 

Q. We moved to a condo with a small yard, and management puts mulch around the plants every year. We are allowed to put in our own small plants, but I was wondering whether it’s a good idea to plant edible things in mulch; who knows what is in it.

J.C., Dover, N.H.

A. You have to be a lot fussier about soil and mulch for plants you are going to eat than for those you are just going to look at. The worst-case scenario is that there is a toxic component in the mulch from recycled pressure-treated wood or demolished buildings. I avoid dyed wood mulch for fear it is disguising questionable origins. Ask the management the origin of the mulch. If it doesn’t seem safe, maybe you can ask them to change it. It may be easier, however, just to ask to grow your edibles in containers or raised beds. Most edible plants prefer this, especially herbs, because it improves drainage. Container gardening would also allow you to control the quality and purity of the growing medium as well as the mulch. Herbs and edibles in attractive containers can be beautiful accents in a landscape. Incidentally, two to four layers of newspaper provide good weed control in vegetable gardens for a season before decomposing. Avoid pages with colored ink, which may contain lead. Water-permeable horticultural plastic is another choice, good for about two years. Cover either with a thin layer of organic mulch to hold them in place and to perk up their appearance.

 

Q. Actually Hyssopus officinalis is the Latin name for true hyssop. The Latin name for anise hyssop is Agastache foeniculum, a very different plant, although also in the mint family. Anise hyssop is a native American biennial, or short-lived perennial, that grows about 3 feet tall. It is covered with purple flowers much beloved by bees in the summer and goldfinches in the fall.

J.M., Guilford, Vt.

A. Thanks! Sounds as if I got my hyssop confused in the last column. This is why we should use botanical Latin names (even if they are difficult to pronounce).

Events

This is the all-too-brief time of year to visit gardens while they are in full bloom.

The Garden Conservancy is sponsoring tours of private gardens throughout the country on various days to support garden preservation, including several in Massachusetts. Visit its website at gardenconservancy.org for locations and dates.

If you are an iris enthusiast, consider joining the Iris Society of Massachusetts. Its annual tour of members’ dazzling gardens is scheduled for June 8. Go to massirises.org for more information.

The new preservationist group Friends of the Spalding Garden is offering a rare opportunity to visit a surviving garden by mid-century modernist landscape master Fletcher Steele on Fletcher Steele Way in Milton on June 9 from 4 to 6 p.m. Free admission.

Global ocean conservationist David Rockefeller Jr., historian Douglas Brinkley, and Grace Chapman Elton, chief executive officer of Tower Hill Botanic Garden in Boylston, were the headline speakers at the annual national conference of the Garden Club of America, the first to be held in Boston in nearly two decades.

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