Guide to June Gardening

June has always enjoyed good press. "What is so rare as a day in June?" wrote the poet James Russell Lowell. "Then, if ever, come perfect days." The nineteenth-century British poet Samuel Taylor Coleridge called it the "leafy month of June." Much later, our American musical lyricist Oscar Hammerstein proclaimed that "June is bustin' out all over," adding many favorable comments about the season. It is the month when gardens reach their peak, and the dog days, with their dust, cicada hum, and ubiquitous daisies, are yet to come.

Of course, Lowell and Hammerstein were writing from a New England perspective, but their views, with minor adjustments, define the classic June across the nation. The month may present different images in various parts of the country, but to most gardeners, it conveys feelings of richness, abundance, and completion. Some important exceptions where June's bounty busts out earlier are the Deep South, the Rocky Mountains, the deserts, and California.

(Note: We list USDA Hardiness Zones for plants to indicate general northern and southern limits of successful plant growth. Remember that even though most plants can grow in many different zones, they often perform differently, blooming later or earlier or needing extra care.)

June Gardening in the North (Zones 3 to 7; 3 to 8 in the Pacific Northwest)

Enjoy the month. Don't work too hard, and take time to enjoy the flowers, your own and those of others. Perhaps it could get better than this. Scan your own garden carefully for underperforming plants, and visit public gardens and nurseries to identify good replacements.

In these regions, perennials reach their peak in June. Peonies, irises, daylilies, and delphiniums peak as phlox come into bud and astilbes begin to light up shady garden spots.

Perennials Peak

Peonies. Opulent double peonies (zones 2 to 8) are the classic June flowers, but single peonies have a simpler, more innocent look without sacrificing size or color, and they generally do not need staking. Scan catalogs for them; suppliers offer some varieties by color and others as named varieties. If you can't find plants in containers now, remind yourself to order some peony tubers next fall.

Irises (zones 3 to 8) and daylilies (zones 4 to 8) carry on the June show. Repeat-bloom (remontant) irises and daylilies are available and will prolong June into fall. Specialists' catalogs can get you up to speed on desirable varieties, and you can order now for delivery later in the summer. In some areas, growers will dig plants that you select so you can immediately replant them in your garden.

Delphiniums (zones 5 to 7) also come in this month. For bloom again in areas where autumn is mild, feed the plants after bloom, cut back spent stalks to 1 foot, and then remove stalks entirely when new growth is 6 inches or so tall. Unless you like leaning delphiniums, be sure to stake them before they grow tall.

Roses and More: Flowering Shrubs

A second wave of flowering breaks in late May and June. Many old-fashioned roses (especially hybrid perpetuals like the rose-pink 'Baronne Prevost', zones 4 to 9 ) repeat the luxuriant look of double peonies. David Austin's English roses (zones 5 to 9) blend the old-fashioned beauty and fragrance of these heirlooms with sturdy, healthy plants in a surprising range of colors and plant sizes. Unlike the stiff and fussy hybrid tea roses, these roses make excellent landscape shrubs. Among the choicest are 'Graham Thomas', yellow flowers on a 4- to 8-foot plant; 'Heritage', shell-pink flowers on a 4-foot shrub; and 'Fair Bianca', white flowers on a 3-foot plant.

To see these and other roses in bloom, visit municipal rose gardens or nurseries. Then visualize a grassy panel bordered with informal groupings of these long-blooming and fragrant shrubs. Or consider using roses to replace a high-maintenance, low-performance hedge.

Classic Flowering Shrubs

Other shrubs that blossom in June are mountain laurel (Kalmia, zones 5 to 8), beauty bush (Kolkwitzia amabilis, zones 5 to 8), mock orange (Philadelphus, zones 5 to 8), and azalea (Rhododendron, zones 5 to 7).

The native mountain laurel (K. latifolia) with pink buds and pinkish white flower clusters has produced offspring with dark red buds ('Sarah' and 'Olympic Fire'), and with strongly marked flowers of dark purplish red and white ('Bullseye'). You can even find dwarf plants only 2 to 2 1/2 feet tall ('Elf' and 'Tiddlywinks'). They like partial shade (although they will take much sun in cool-summer regions), ample moisture, and acid soil, as do the deciduous azaleas whose bloom periods straddle late spring and early summer. All these shrubs are available from specialty catalogs if your nursery does not stock them.

Formerly notable chiefly as a parent of the showy Knap Hill and Exbury hybrids, the native flame azalea (R. calendulaceum, zones 5 to 7) lights up miles of Appalachian woodland with its yellow, red, or orange flowers. Paler, but making up in fragrance what it lacks in brilliance, the swamp azalea (R. viscosum, zones 3 to 9) produces clusters of clove-scented white to pink flowers on bushes 6 to 8 feet tall.

A relatively new group of deciduous azalea hybrids, Northern Lights (zones 3 to 8), is the answer to the gardener's need for azaleas that can withstand -40°F temperatures and still bloom. The plants grow 6 to 7 feet tall and as wide. Their lightly fragrant flowers vary from white ('White Lights'), to yellow and apricot ('Golden Lights' and 'Apricot Surprise') and lilac and pink ('Orchid Lights' and 'Rosy Lights').

Beauty bush seems to have received far less attention than it deserves. Its 1901 introducer, E. H. Wilson, claimed that it was one of his finest Chinese introductions, but later experts have had much fainter praise. According to Michael Dirr, horticulturist with the Department of Horticulture at the University of Georgia, the flowers are magnificent, but the plant is a headache for the rest of the year. He refers to its height (6 to 10, possibly 15, feet tall); its arching, fountain-shaped top; and its scantily furnished lower stems. No one questions the beauty and abundance of the yellow-throated pink blossoms. Plant it in the background, and mask its bare legs with lower shrubs, or cut it to the ground after flowering.

Mock Oranges. Gardeners could lay the same charge against most mock oranges. They do become tall and leggy, and they're unremarkable when not blooming, but they deserve a place in the garden for their fragrance. Although many varieties can reach 6 to 15 feet tall, modest-sized varieties include 5-foot 'Galahad' and 'Glacier', and 2- to 3-foot 'Dwarf Snowflake'.

If you miss the lilacs of May, don't grieve: Extra-hardy Preston lilacs (Syringa prestoniae, zones 3 to 7) may still be blooming in June. 'Miss Canada', relatively new, has reddish buds and deep-pink flowers.

Higher Up: Flowering Trees

Dogwood. June-blooming trees are worth thinking about. Flowering dogwood (Cornus florida, zones 5 to 9) has finished blooming by June, but Kousa dogwood (C. kousa, zones 5 to 8) not only prolongs bloom into June but promises to be resistant to the pests and diseases that have made life precarious for our native varieties. 'Milky Way' is an exceedingly heavy flower-producer, and 'Miss Satomi' (also called 'Rosabella') has deep pink flowers.

Smoke Tree. Depending upon your point of view, smoke tree or smoke bush (Cotinus coggygria, zones 4 to 8) is a treelike shrub or shrubby tree (to 25 feet). Either way, it puts on a flower show of no great beauty but follows with spectacular clouds of fruit stalks decorated with silky hairs. The 6- to 8-inch clusters vary from creamy tan to a rich pink and create the impression of smoke puffs. The fall foliage is brilliant, with tones of yellow, orange, and red. Many purple-leaved forms exist, such as 'Velve Cloak' and 'Royal Purple'. Also look for the hybrid 'Grace', a new variety that features somewhat larger leaves and "smokes," and red-orange fall color.

Magnolia. Northern gardeners who really want their garden to reach upward might consider planting 'Edith Bogue' evergreen magnolia. Although evergreen magnolia (M. grandiflora) is southern in origin, plants of 'Edith Bogue' spring from a plant growing in Montclair, New Jersey. Huge white fragrant flowers appear in June and sporadically throughout the summer. Stiff, leathery, dark green foliage will profit from a position sheltered from winter winds and drying winter sun. The tree grows to 35 feet and is hardy in zones 6 to 9.

June's Sunny Chores

This month is not all fun and games. You have work to do. If you secure some of the delights listed in this article from your nursery, you must plant them. The first step is to check your soil. If it's sandy or stiff with clay, dig in humus to improve water retention and aeration. Well-rotted manure or compost are highly desirable, but other materials are useful, too: rotted sawdust, ground corncobs, or cocoa shells.

Planting Container Plants. When setting out container-grown plants, be sure that the soil is moist (not wet) and that you have watered the plant itself. One cause of loss in new plantings is that the rootball is dry and sheds water when irrigated. The danger is especially great with the peat-based soil mixes used for growing azaleas, mountain laurels, and rhododendrons. If one of these plants should show signs of wilt shortly after planting, moisten the rootball by setting a hose at the base of the stem and letting water trickle very slowly until the soil becomes thoroughly wet.

After removing the plant from the container, straighten any tangled roots, and cut a few shallow slashes along the side to encourage root branching. Be sure that the base of the plant is very slightly above grade level to reduce the chances of water accumulating at the soil line andcausing rot. Large shrubs or trees need a watering basin for deep soaking in the hot days ahead. Apply a mulch to keep soil cool and keep down weeds, but keep it a few inches away from trunks.

Water. Watering becomes critical this month in many regions. Plants in active growth draw heavily on soil water, and hot winds easily damage soft young growth. Keep an eye on weather reports, and try to water before rather than during a heat wave. Simplify your life by adding a drip-irrigation system with automatic controls, but keep an eye on your garden. Overriding the controls or using supplementary irrigation might be necessary.

June Gardening in the South (zones 7 to 10)

Gardeners in the South enjoyed their June earlier, in May or even April. The lower the latitude, the earlier the high season. An old classic June bloomer in cooler areas, 'Lord of June' tall bearded iris, may open in April or May in the South.

Hydrangeas that will not bloom until July in the Northeast are June performers in the South. The big white, pink, or blue hortensias (Hydrangea macrophylla, zones 6 to 9) are now available in smaller varieties. 'Forever Pink' reaches 2 to 3 feet, with somewhat greater spread, and its 4-inch flower heads appear from June to frost, fading from pure pink to deep rose. 'Pia' is even smaller: 2 feet tall and broad, with purple-toned pink flowers in 4- to 5-inch clusters. Oakleaf hydrangea (H. quercifolia, zones 5 to 9) produces its tall pyramidal white flower clusters this month. Its flowers age to pink, and the bold oakleaf foliage takes on handsome maroon to purple tones in the fall. 'Snowflake' and 'Snow Queen' have been selected for bloom quality.

Crape myrtles (Lagerstroemia, zones 7 to 9) do not peak until late summer, but a few varieties-white semidwarf 'Acoma', lavender 3-foot dwarf 'Centennial', tall dark red 'Centennial Spirit', pink semidwarf 'Hopi', and tall white-flowering 'Natchez' are likely to blooming in June.

Butterfly bushes (Buddleia, zones 5 to 9) provide long bloom beginning in late June. They also attract butterflies. Pruning presents no complications; cut the stems nearly to the ground each spring. Improved varieties include: B. davidii 'Dartmoor', with dense, many-branched flower clusters; and the Nanho series (B. d. nanhoensis), compact growers with flowers in blue, purple, or white.

Rose of Sharon (Hibiscus syriacus, zones 5 to 9) is considered a late-summer bloomer, but it often starts to bloom earlier in the South. Newer varieties of these tough, tolerant shrubs with a long bloom season have sterile flowers that produce no unattractive seed capsules and no unwanted volunteers. 'Aphrodite' is pink with a red eye, 'Diana' pure white, 'Helene' white with a deep red eye, and 'Minerva' deep lavender with a dark red eye.

June Gardening in the Rockies (zones 3 to 7)

In the Rocky Mountains and high-desert areas of the Southwest, June is not a month for languor. Everything needs doing. You must plant trees, shrubs, and perennials in June so they can sink in their roots before early frosts. Set out bedding plants after the last frost. Crackling dry air and uncertain rainfall in these regions make careful attention to irrigation a necessity. Take special care to water plants under roof overhangs; they don't receive moisture from summer rains, and the death by drought of otherwise hardy plants is sometimes mistakenly attributed to winterkill.

New Plants. For new plant ideas, the Denver Botanic Garden has extensive outdoor plantings, including a remarkable rock garden, with mountain plants from all over the world. Some of these are ground covers that make good choices for small areas. Beard tongue (Penstemon pinifolius, zone 8), a native of the southern Rockies, is a 6-inch mound spreading to 2 feet in width. Its tiny leaves are needlelike, and the flowers are bright red (or, in the variety 'Mersea', bright yellow). P. linarioides (zone 4) is similar, but with lilac to purple flowers. From Turkey comes Veronica liwanensis (zone 6), an inch-tall sheet of bright blue flowers in late spring and summer. From South Africa come two hardy ice plants: Delosperma nubigenum with bright yellow flowers and D. cooperi with rich purple blooms. Both plants have succulent green leaves that turn red in winter.

June Gardening in the desert (zone 9; zone 10 areas of southern California and Arizona)

In the lower deserts of Arizona and California, June is a month of harvest rather than planting, although hot-weather annuals such as cockscomb, Madagascar periwinkle, portulaca, and annual salvias may be planted early this month for summer bloom.

Palm Planting. June is also the ideal time to plant palms: Dig a hole twice as wide as the rootball, thoroughly break up any caliche (hardpan) at the bottom of the hole, and add plenty of organic matter when backfilling. Water thoroughly, stake or guy if the palm is large, and tie up the fronds above the growing tip to protect the bud from sunburn.

Newcomers to the desert may think that the plant selection is meager. In fact, plants are being introduced every year. To see some possibilities, visit one of Arizona's great desert botanical gardens. The Arizona-Sonora Desert Museum has attractive demonstration gardens with plants native to the region.

June Gardening in California (zones 3 to 9)

California's varied terrain offers diverse June garden scenes. On the cool north coast, fuchsias and geraniums gleam against the fog-washed green of redwoods and rhododendrons. Farther south, bougainvillea and hibiscus add dramatic color. In the Central Valley, blazingly hot but well irrigated, gardens grow with tropical exuberance.

Everywhere in the state, water districts and other public agencies, as well as landscape professionals, urge the use of plants that require little summer water. California natives, and plants from Australia, South Africa, the Mediterranean, and other regions with dry summers, are coming into gardens in waves.

John R. Dunmire is encyclopedia author of the Sunset Western Garden Book and the Sunset National Garden Book (Sunset Publishing Corp., Menlo Park, CA).

Photography by Suzanne DeJohn/National Gardening Association

Article published on June 23, 2008.

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