SPRING is an exhilarating time for gardeners as we look to update and enhance our home landscapes with the latest and best in woody and herbaceous plants.
Each year, the collective efforts of plant breeders and the nursery industry culminate in the release of a handful of new plant cultivars. These improved selections may represent new species for our region (like Northern Pin Oak) or offer enhancements over existing cultivars such as a novel growth habit and enhanced flowering.
Let's look at several exciting new additions in cold hardy trees, shrubs and herbaceous perennials.
Goldspur is a compact selection of Amur cherry that I selected while residing in Saskatoon in the late 1990s. Goldspur conforms to the definition of a small ornamental tree that has become increasingly important with smaller residential lot sizes.
The plant has a unique habit of producing a dense, rounded crown with tufts of emerald-green foliage.
The secret to Goldspur's unique form is its very short internodes (the spaces between adjacent leaves). The densely arranged leaves create attractive radiating tufts of foliage on every branch. Goldspur retains the desirable features of Amur cherry, including exfoliating golden bark and racemes of white flowers, which mature into clusters of tiny black fruit.
Oak represents a challenging yet exciting genus in our quest for expanded shade tree diversity. Oaks are known for their longevity in the natural landscape but often prove to be difficult to transplant and maintain in sites affected by human activities. Manitoba's sole native oak species, bur oak, is well-represented in Winnipeg's urban forest, but mature trees are also declining in many areas of the city.
In Manitoba, our alkaline soils (pH 8) make it very difficult to grow other oak species such as Northern Pin Oak. But what if it were possible to graft a Northern Pin Oak onto the well-adapted root system of our native bur oak? After all, we follow a similar path with ash, where the durable green ash serves as the rootstock for production of black, white, manchurian and hybrid ash.
'Shooting Star' is a cultivar of Northern Pin Oak selected near the Lake of the Woods by Rick Durand. It is propagated by grafting buds of the parent tree onto seedling bur oak. It features the attractive bristled foliage of the red oak group combined with outstanding red fall colour: a rarity on trees grown in Manitoba. The fall colour is reliable and robust, with the glossy crimson foliage holding on through early fall frosts.
The list of new hydrangea cultivars seems to grow with each passing year. The newest member is Vanilla Strawberry, a well-named hydrangea brought from France to North America by Bailey Nurseries. The name invokes thoughts of a lovely blend of two popular ice-cream flavours and aptly describes the colours in maturing flower clusters. Flowers emerge white, but change to a bright red colour that persists for a month.
Invincibelle Spirit has been greatly anticipated as the first pink-flowered form of Annabelle hydrangea. This new cultivar is a continuous bloomer from mid-summer to fall, producing lovely pink-flowered ball-shaped inflorescences. Invincibelle Spirit was developed by Dr. Thomas Ranney, NCSU, and is presently marketed by Proven Winners. For every Invincibelle Spirit hydrangea sold, one dollar will be donated to the Breast Cancer Research Foundation.
Cool Splash is a variegated selection of Diervilla sessilifolia. Back in July 2008, I was introduced to this plant during a tour of the research plots at Bailey Nurseries in St. Paul, Minn. It made an immediate impression with its mounded growth habit, disease-free foliage and panicles of golden-yellow flowers.
Cool Splash originated from the Landscape Plant Development Center, source of other recent introductions including Center Glow Ninebark. Founded in 1990 by Dr. Harold Pellett, the Landscape Plant Development Center has a mission to develop new, superior landscape plants with an emphasis on those that are more tolerant of biological and environmental stresses.
Cool Splash is a fast-growing, very attractive shrub with striking foliage. Its crisp, strap-like leaves have green centres and white margins. Cool Splash reaches a maximum height of about one metre.
The question that remains is cold hardiness. Numerous sources, including Bailey Nurseries Inc., have claimed that Cool Splash has zone 3 hardiness, which should permit reliable survival in areas of the Prairies with consistent winter snow cover.
Northern Dazzle and Northern Delight are the latest orientpet lilies from Jeffries Nurseries. These new cultivars will add fresh colours and shapes to the original red and white collection. They are the result of work by well-known hybridizer Robert Griesbach of Wisconsin. Selected by Wilbert Ronald of Jeffries Nurseries, they have proved to be cold-hardy, vigorous and disease-resistant in zone 3.
Northern Dazzle features a bi-coloured flower with a red centre and yellow margins. The six-inch blooms are side-facing, with six to 10 blooms per stem. The stems are strong and average 1.3 metres in height. Lightly scented, it blooms in late July/early August.
Northern Delight produces yellow flowers that are exceptionally large (eight inches across), and side-facing with a more classic trumpet form. Northern Delight can have up to 20 blooms borne on strong 1.3-metre stems. It blooms in late July/early August. The flowers do not have a strong fragrance.
Visit your local garden centre later this spring to acquire your own sample of these outstanding new landscape plants.
Dr. Philip Ronald was educated in plant breeding and horticulture at the University of Manitoba and University of Saskatchewan. He contributes to the research and marketing programs at Jeffries Nurseries Ltd. in Portage la Prairie.
