Gardening Guides
Great Lakes Gardener's May Checklist
Let's talk about brilliant flowering trees. About blooms to light up a shade garden. And, of course, about everyday garden tasks
May is the most glorious month of the year in the Great Lakes garden. Trees and shrubs burst into bloom, the shade garden hits its peak of beauty and the weather is just about perfect. With the passing of the last frost date, you can bring tender annuals into the garden, but with the warmer weather come garden chores that you must do now. If only there were more days in May.
Lilacs (Syringa vulgaris, zones 3 to 7) are tough, long-lived fragrant spring standards. Although not native, they are associated with the Midwest because of the 19th-century pioneer practice of planting lilacs near outhouses. The strong scent of lilacs is nostalgic for many people, making them very popular; there is even an annual Lilac Festival in Lombard, Illinois. They are perfect for incorporating into heritage and cottage gardens.
Syringa vulgaris may be prone to powdery mildew. Dwarf Korean lilacs (Syringa meyeri, zones 3 to 7) are not prone to powdery mildew and bloom slightly later than common lilacs.
Syringa vulgaris may be prone to powdery mildew. Dwarf Korean lilacs (Syringa meyeri, zones 3 to 7) are not prone to powdery mildew and bloom slightly later than common lilacs.
One of the best underused shrubs blooming in May is the native pagoda dogwood (Cornus alternifolia, zones 3 to 7). Its elegant tiered branching structure makes it attractive during all seasons. It thrives in shade and lightens the garden during May.
For an unparalled floral display, nothing beats tree peonies (here Paeonia suffruticosa 'Ofuji-Nishiki', zones 4 to 9). The dinner-plate-size blooms have a light fragrance and open before the herbaceous peonies. These 4- to 6-foot-tall woody shrubs bloom in a range of colors from white to yellow to red to purple. The fragile blooms last longer if the plant is sited in partial shade, preferably with morning rather than afternoon sun. Who needs rhododendrons?
The shade garden reaches its peak in May, with big, bold natives such as Solomon's plume (Smilacina racemosa aka Maianthemum racemosum, zones 3 or 4 to 7, shown here with the native Geranium maculatum) and later Solomon's seal (Polygonatum biflorum var. commutatum, zones 3 to 9). Their white blooms glow in the shade.
Along with the nonnative columbines, the red and yellow native Aquilegia canadensis (zones 3 to 8) blooms in May, providing nectar for hummingbirds.
Foamflowers (Tiarella 'Iron Butterfly', zones 4 to 9, shown) and coralbells (Heuchera hybrids, zones 4 to 8) send forth fluffy flowers, while wild blue phlox (Phlox divaricata, zones 4 to 8) scent the air with sweet blooms.
The ephemerals make their big display now, and it wouldn't be May without mayapples (Podophyllum peltatum, zones 3 to 8). These large, spreading plants need careful siting, as they form large colonies that can leave a gaping hole when they die back. The edible fruits ripen in June.
Trilliums (here Trillium grandiflorum, zones 4 to 8), Dutchman's breeches (Dicentra cucullaria, zones 3 to 7), shooting stars (Dodecatheon meadia, zones 4 to 8) and spring beauty (Claytonia virginica, zones 3 to 8) make a brief but showy appearance before disappearing in the summer heat.
While not a typical flower, jack-in-the-pulpit (Arisaema triphyllum, zones 4 to 9) does bloom. Despite being a native plant, the foliage provides a tropical feel before it disppears during the summer, leaving stalks of bright orange fruits.
Well-behaved exotics can add to the May shade garden, such as brunnera (Brunnera macrophylla 'Jack Frost', zones 3 to 8), Epimedium and primroses (Primula spp). Lily of the valley (Convallaria majalis, zones 2 to 7) needs to be sited in a confined area where it will not overrun.
Straddling the border of sun and shade, meadow rues (here Thalictrum aquilegifolium 'Thundercloud', zones 5 to 9) ask only for moist soil. Native Jacob's ladder (Polemonium reptans, zones 3 to 8) prefers the same lighting conditions.
In the sunny garden, the tulips and daffodils are making their swan song, and the alliums, such as this Allium aflatunense 'Purple Sensation', round out the season. Planting tall alliums amongst daylilies (Hemercallis) and hostas will help conceal the unsightliness of the yellowing foliage after bloom.
Bearded iris (Iris germanica hybrid shown) season begins in May, with the dwarf bearded irises early in the month, then the tall hybrid cultivars later. Reblooming irises, such as the white 'Immortality' and the purple 'Rosalie Figg', do double duty by blooming again in the fall.
The beardless irises also begin their season in May. The earliest of the Siberian irises (Iris sibirica) begin blooming in May, while the late-blooming cultivars wait until June. The iris native to the Great Lakes is the wetland blue flag iris (Iris virginica var. shrevei). Easier to incorporate into a garden is the tiny beardless crested iris (Iris cristata shown), which is native to parts of the United States but not the Great Lakes region. It likes a bit of shade and makes a good ground cover.
Garden Tasks
Plant summer annuals. Once the last frost date has passed, it is probably safe to plant tender annuals, such as sweet potato vine (Ipomoea batatas 'Marguerite'), shown here with petunia 'Pretty Much Picasso'. Plant Angelonia, fuchsia and dahlia. You can also plant tomatoes and peppers now.
Support plants. Put in supports for tomatoes and other plants before the need arises, especially stakes for tall lilies and hoops for herbaceous peonies (Paeonia lactiflora cvs). Attaching individual stems to supports with a flexible material will prevent breakage in high winds or heavy rain.
Mulch before things heat up. Get mulching before the heat of summer dries out the soil. There are various types of mulch available, but the best for the sunny and edible garden is compost. If you don't have enough, you can purchase it bagged; many municipalities also offer compost free to residents. For the shade garden, nothing is better than leaf mold, which is rotted leaves. Absent that, shredded leaves make an adequate substitute. If that looks too messy, you can use finely shredded, partially rotted hardwood mulch. Save the coarser mulch for use on paths. Renew mulch throughout the growing season to keep soil moisture in and to insulate against the heat.
Divide snowdrops (Galanthus spp) "in the green." Snowdrops prefer this treatment, and it's easier than trying to find and dig them up after they've gone dormant. Replant them immediately.
Get out the patio furniture and scrub it down to make it ready for grilling season and Memorial Day weekend. Then pour a glass of cold lemonade, sit back and enjoy the garden.
More regional gardening guides
Plant summer annuals. Once the last frost date has passed, it is probably safe to plant tender annuals, such as sweet potato vine (Ipomoea batatas 'Marguerite'), shown here with petunia 'Pretty Much Picasso'. Plant Angelonia, fuchsia and dahlia. You can also plant tomatoes and peppers now.
Support plants. Put in supports for tomatoes and other plants before the need arises, especially stakes for tall lilies and hoops for herbaceous peonies (Paeonia lactiflora cvs). Attaching individual stems to supports with a flexible material will prevent breakage in high winds or heavy rain.
Mulch before things heat up. Get mulching before the heat of summer dries out the soil. There are various types of mulch available, but the best for the sunny and edible garden is compost. If you don't have enough, you can purchase it bagged; many municipalities also offer compost free to residents. For the shade garden, nothing is better than leaf mold, which is rotted leaves. Absent that, shredded leaves make an adequate substitute. If that looks too messy, you can use finely shredded, partially rotted hardwood mulch. Save the coarser mulch for use on paths. Renew mulch throughout the growing season to keep soil moisture in and to insulate against the heat.
Divide snowdrops (Galanthus spp) "in the green." Snowdrops prefer this treatment, and it's easier than trying to find and dig them up after they've gone dormant. Replant them immediately.
Get out the patio furniture and scrub it down to make it ready for grilling season and Memorial Day weekend. Then pour a glass of cold lemonade, sit back and enjoy the garden.
More regional gardening guides
While there are many flowering trees that struggle here in the Great Lakes, the crabapple (here Malus 'Prairiefire', zones 4 to 8) reliably provides a brilliant show every year. The sweet crabapple scent fills the air from branches so laden with blooms that it looks as if pink, red and white clouds have descended. If you plant varieties that bloom at different times, your crabapple show can last for a month.
Crabapples are versatile, with forms ranging from weeping to wide spreading and heights ranging from the 5-foot-tall 'Tina' up to 20 to 25 feet for many cultivars, making them suitable for planting under power lines. They need full sun and are adaptable to most soil conditions. Look for disease-resistant cultivars.