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Helianthemum 'Hartswood Ruby'

Joe Kunkel and Hartswood RubyThere’s a great deal of color in the Bressingham Garden this month. Yellow. Pink. Check. Check. Blue. Check. Lavender. Check. But how about red? Really, really, red?

Check.

It’s there in the form of a wonderful, low mounding group of plants by the name Helianthemum ‘Hartswood Ruby’. And, remarkably, it’s getting redder by the day. It’s also remarkable that it’s there at all.

Let’s start with the name. ‘Helianthemum’ sounds like one of those exotic crossbreeds developed in the past few years. In point of fact, the genus (pronounced (hee-lee-AN-thee-mum), goes back to 1754 and there are some 650 cultivars on record. ‘Hartswood Ruby’, though, dates only to 2007 when Blooms of Bressingham introduced it to the world. It was planted that same year in the Bressingham Garden at Elm Bank.

If you recall, the winter of 2007-2008 was a mild one. Plants and perennials that were marginal to Zone 5 came through fine. This past winter was a much more severe test. Lots of snow, but also lots of cold. When Hartswood Ruby – which is officially designated hardy only to Zone 6 - was uncovered in early April, things didn’t look so good. There was lots of die-back, especially in the centers of the fifteen or so specimens. But there was also some nascent greenery. The plant, a favorite of Mass Hort executive director Joe Kunkel, went on the ‘watch list’.

By early May, Hartswood Ruby was covered in narrow, glossy, dark green leaves, with only a modest amount of die-back on each mound. By mid-May, each plant was a three-foot-wide mound of dark green and there were a sprinkling of velvety red flowers. At this writing (May 26), the sprinkling has become a torrent. Originally planted on 36-inch centers, the plants now form a solid mass stretching some fifteen feet in length and up to six feet wide. Hartswood Ruby is back with a vengeance.

The flowers – hundreds of them on each plant – are saucer-shaped (hence one of its nicknames, ‘rock rose’) and a little less than an inch wide. The stamens are bright gold and a delightful contrast. The best part of the story is that, if 2009 is like 2008, the flowers will persist well into July, a month after most Helianthemums have spent their energy. One source says Hartswood Ruby will re-bloom in the fall, though I don’t remember seeing its distinctive flowers last autumn.

Caring for Hartswood Ruby is easy. It thrives in well-drained neutral to alkaline soil and it wants full sun. It is drought-tolerant once established and deadheading will help prolong the bloom. If the specimens at Elm Bank are any indication, Hartswood Ruby wants to spread, so some trimming may be required to keep it from becoming leggy.

In the Bressingham Garden, Hartswood Ruby is growing near the principal garden entrance (on the side adjacent to the Italianate Garden) and is readily identifiable by its distinctive color and huge mass. Part of the mound nestles against several large rocks place there for just such contrast, lending support to the recommendation that the cultivar works well in alpine or rock gardens. There’s another recommendation from one nursery that Hartswood Ruby is suitable for window boxes, though its vigorous growth habit might make it less suitable for such use.

About the Massachusetts Horticultural Society

Mass Hort logo newFounded in 1829, the Massachusetts Horticultural Society is dedicated to encouraging the science and practice of horticulture and developing the public's enjoyment, appreciation, and understanding of plants and the environment.

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