A website from UGA Cooperative Extension

by Marty Thomas, Fulton County Master Gardener Extension Volunteer

This article is part of Garden Buzz, a series from Appen Media and the North Fulton Master Gardeners, where rotating columnists explore horticulture topics like herbs, insects, and wildlife conservation. Find all Garden Buzz articles here.

May has arrived and the days are getting warmer and longer. It’s time to tidy up spring plants and start planting summer bedding plants. According to the 2023 USDA Hardiness Zone Map, Atlanta is in zones 8a and 8b. This is a change from the 2012 map, which had Atlanta in zones 7b and 8a. This is due to climate change. There are 13 growing zones across the country, and each zone represents a 10-degree range of average temperatures in winter. Zone 8 is a warm zone with a long growing season, mild winters and hot summers.

What are some of the best plants that can be planted in the month of May in the Atlanta area? Read on to learn more.

Irises begin blooming in April and May. Image by the author.

Flowers can add color to your landscape and attract pollinators, like bees, butterflies, and hummingbirds. Some annuals include begonias, lantana, salvia, petunias, coleus, caladiums, vinca, impatiens, petunias, geraniums, and zinnias. Perennials, which come back each year, could include coneflowers, black-eyed Susans, Shasta daisies, daylilies, Russian sage, coreopsis, blanket flower, phlox, dahlias, yarrow, hostas, asters and sedum.

May is a good time to divide and transplant perennials. It’s the perfect time to divide hostas as they come into growth. Iris usually begin blooming in April and May. The best time to divide them is about six weeks after blooming. Roses will begin blooming in May, and climbing roses and any rambling roses should be tied up and secured. Check for blackspot and treat with a systemic fungicide if necessary.

Roses put on a show in May. Image by the author.

Flowering shrubs like hydrangeas, butterfly bushes, spirea and hibiscus can be planted now. There are two types of hibiscus, hardy and tropical. The hardy variety is a perennial whereas the tropical variety is treated as an annual in zone 8. Rose of Sharon and Confederate Rose are both in the hibiscus family. Spring and early fall are the best time to plant these flowering shrubs.

Herbs such as rosemary, lavender, dill, basil, oregano, thyme, and sage can be planted now. Pinch herbs back to promote bushy growth. Cilantro should be planted earlier because it likes cooler temperatures and will bolt in summer heat. What does it mean to bolt? Bolting is common in heat-sensitive plants such as green leafy vegetables like lettuce, cabbage, broccoli, cauliflower and bok choy. Bolting is a horticultural term for when a plant prematurely develops a flowering stalk in order to produce seeds.  This is often called “going to seed’. May is a good time to harvest leafy green vegetables.

Some vegetables good to plant this time of year are squash, tomatoes, peppers, cucumber, okra, beans, corn, Brussels sprouts and onions. Have a trellis system in place for tomato plants and pole beans before they begin to sprawl. If seedlings were started indoors, now is a good time to start hardening off frost-tender plants. This means to put them outside for a short period of time each day for several days to get them used to outside temperatures. The ground is warm enough in May to sow seeds outdoors. Both vegetable and flower seeds can be sowed at this time.

Fencing around raised beds will keep out deer and can also be used for trellises. Image by the author.

It is safe now to plant almost anything outdoors, including tender annuals like impatiens. Houseplants can even be moved outside to a shady spot for a summer vacation. Now is a good time to feed your potted plants using a balanced fertilizer. This means using a fertilizer, such as 10-10-10, meaning it has balanced proportions of NPK (nitrogen, phosphorus and potassium). Top dress permanent potted plants to refresh compost. Weed beds and borders and add more mulch if needed.

Fruits and fruit trees can be planted now. Some good fruit trees to plant are apple, cherry, apricot, fig, pear, peach, plum and citrus fruits. Trees such as southern magnolia, dogwood and crape myrtle can also be planted now.

Now’s the time to look after your finished spring bulbs. Do not cut back the green foliage because it provides nutrients to what will become next year’s bulbs. Simply let the foliage die back, turn brown and then clean up. I sometimes tie up bundles of daffodil leaves and secure them with a rubber band until they dry up.

Mid-May is a great time to propagate cuttings for flowering shrubs like spirea, lilac and viburnum. FYI, you can make more plants from cuttings than from division. Simply take a cutting with at least three buds on it, dip into rooting hormone powder and plant in a pot until big enough to transplant.

Keep an eye out for pests and insects in the garden. Aphids are common and can be sprayed off with a strong jet of water or use insecticidal soap. Ladybugs are good insects to have around because they eat aphids. Contact your local Extension office for help identifying and managing insect pests.

You might want to keep a gardening journal and list seeds sowed and plants you’ve planted. Take time out to enjoy your garden now that the warm weather has arrived!

Happy May gardening!

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About the Author

This week’s “Garden Buzz” guest columnist is Marty Thomas, a master gardener since 2018 and a resident of Johns Creek. A former teacher, she continues working with children through substitute teaching, children’s art camps, and children’s ministry. Marty is on the board of directors for the Johns Creek Beautification Committee and a member of the American Hydrangea Society.  She leads a Bible study discussion group at her church and loves spending time with her grandchildren.