Summer Flowering Azaleas—Extend the Season

Mention the name of the late Ed Mezitt of Weston Nurseries in Maine to anyone in the ornamental plant business, and such famous rhododendrons as ‘PJM’, ‘Aglo’, ‘Olga Mezitt’, ‘Westons Pink Diamond’ and many more are bound to be discussed.

A desire to expand the variety of early flowering shrubs led Ed, in the 1950s, to develop the PJM hybrids, including ‘PJM’ itself, named after his father, Peter J. Mezitt.

Mention the hardy rhododendron ‘PJM’ to many gardeners, and they will often wax eloquent on its stunning performance each spring.

‘PJM’ is now the most dependable hardy rhododendron for use in zones 4 to 6, and milder areas as well. It flowers in late April or early May at about the same time as Forsythia. Ed Mezitt spent the rest of his life hybridizing and selecting early flowering hybrids suitable for colder climates. Not as well known are the many other hardy azaleas that originated at Weston Nurseries. One very interesting group Ed Mezitt began to develop in the 1940s is only now starting to enter the mainstream gardening world. These are summer flowering azaleas developed to extend the flowering season. They begin flowering after mid June and will add colour to a garden after most woody shrubs have finished flowering. The four listed here are hardy to at least -30°C which includes zone 5 and many areas in zone 4 as well.

Like all other azaleas and rhododendrons they need an acid soil but grow best in full sun. They will tolerate part shade but are not recommended for areas in full shade. All four may be used to extend the season of the earlier flowering Exbury and Ghent groups of azaleas (all developed in Europe) that have been available for decades and the new hardy Northern Lights azalea series (developed in Minnesota) and finally available on a consistent basis. Included in this series are “Golden Lights’, “Mandarin Lights’, ‘Northern High Lights’, ‘Orchard Lights’, ‘Rosy Lights’, ‘Spicy Lights’ and ‘White Lights’.

The summer flowering azaleas include Lollipop, Pink and Sweet, Popsicle and Westons Innocence:

Lollipop—Flowers are pink with a light pink and yellow flare. Extremely fragrant, they come into bloom in mid-June. By late June the flowers mature to silvery pink and continue to add fragrance to the garden. Their growth habit is wide, and relatively slow. Foliage is disease resistant and leaves a showy red-orange from September into October before dropping.

Pink and Sweet—Masses of pink flowers cover the plants from late June into July in southern Ontario according to plantsman Tom lntven of Canadale Nurseries. Each flower is pink with a lighter pink and yellow eye that matures to a silvery pink. The fragrance is rich and spicy. Plants form an upright mound growing less than 20 cm (8”) a year. The longer green leaves turn bronze in summer then purple-red with tones of orange and yellow in autumn. Again, no mildew has been seen on the foliage.

Popsicle—Flowers are dark pink with an orange flare and fragrant in mid- to late june. Foliage turns burgundy in the fall. Growth upright.

Weston’s Innocence—This is a heavy flowering cultivar with strongly scented small white flowers in July. Plants are vigorous with upright branches becoming mound-shaped with age. Foliage is slightly glossy with a bronze coat in the summer. The fall colour is burgundy-red. In addition to these cultivars which will be generally available across Canada this year, there are many others already performing well at Weston Nurseries and other affiliated growers. In the yellow-flowered category ‘Lemon Drop’ appeared totally mildew resistant in British Columbia last year; and it flowered well. It could be generally available as early as next year. Red-flowered ‘Millennium’ blooms in July and holds excellent promise. Another up-and-coming pink is ‘Pennsylvania’ which starts into bloom the second week of July, in Maine. Other pinks to watch for in the future are ‘Parade’, ‘Sparkler’ and ‘Ribbon Candy’. If you are looking for yellow varieties, seek out ‘Siskin’ an older Ghent hybrid that, unlike others subject to mildew in the summer, exhibits little or no mildew.

Larry Sherk is chief horticulturist for Sheridan Nurseries Ltd. in Toronto.