In the Northern Hemisphere, the month of June is the height of the gardener's growing season. The number of daylight hours peaks with summer solstice, when warm weather invites outdoor celebrations. Weddings, graduations and barbecues all benefit from flowers that are in season in June. A wide variety of perennials, annuals, vines and flowering trees all step up to bring fragrance, color and form to the June landscape.
Hollyhocks (Alcea rosea) are traditional garden plants that bring tall, colorful flower spikes to perennial beds, fences and walls. Hardy to minus 50 degrees Fahrenheit, hollyhocks stand 5 to 8 feet high with a 2-foot spread. Heart-shaped, green leaves become smaller as they ascend the stems. Between June and August, according to the Missouri Botanical Garden, hollyhock produces dramatic spires of 4- to 5-inch blooms. Colors include, white and shades of yellow, pink and red.
Leaves may suffer from spider mites, leaf spot or rust, but its flowers are seldom bothered. A biennial, hollyhock produces leaves in its first year and blossoms in its second. Plant it in full sun and averagely moist, well-drained soil. Leaving spent flowers on the plants will allow them to set seed and self-sow for years of bloom.
Vinca (Catharanthus roseus) is a low-growing perennial in its native home of Madagascar. Hardy to 30 degrees F, it's a mounding plant with glossy, dark green foliage. From June to frost, however, its leaves often disappear beneath abundant blooms. The tube-shaped, red-centered pink blooms resemble those of phlox. Vinca cultivars are available in a wide range of colors from white to pale and deep pink shades, as well as red and lilac.
Use vinca, recommends the Missouri Botanical Garden, in containers, as border edging or as an annual ground cover. Plant it in full sun to partial shade and moist, well-drained sandy loam. Water regularly from underneath. This plant is an exceptional performer in heat and humidity.
Oriental Poppy 'Allegro'
Oriental poppy (Papaver orientale) is a June- and July-blooming perennial. Hardy to minus 40 degrees F, the "Allegro" Oriental poppy cultivar grows up to 18 inches high, and wide, with serrated, lance-shaped greenish-gray leaves. Its 4-to-6-inch, bright orange flowers have papery petals around a showy center of deep purple stamens. Foliage dies back after flowering, but reemerges in fall and persists until plants bloom again the following spring.
Use 'Allegro' in perennial borders full sun and fertile, averagely moist, well-drained soil, suggests the Missouri Botanical Garden. Plants in poorly drained locations are vulnerable to root rot, especially where winters are wet. Provide winter mulch while the poppies are establishing, and stake them if necessary. Oriental poppies do not perform well in high heat and humidity. (References 3 and 4)