Xela's Garden

Rock Rose ...Helianthemum 'Ben Hope'

Genus: Helianthemum.

Species: Helianthemum nummularium.

Planted ? Vistabile lounge front border

Source ?

Evergreen ground cover for borders and rockeries in warm, sunny and moderate dry positions. A good mix of colours including yellow, orange, pink and RED prostrate habit.

Rock roses are a familiar group of plants mainly represented in cultivation by a single species, Helianthemum nummularium that has numerous cultivars. There are roughly 100 species of Helianthemums originally from North America, Europe, West Asia and North Africa. The name Helianthemum is from the Greek helios suggesting sun and anthemon meaning flower. They belong to the family Cistaceae.

Cistacease (the rock rose family) is a small family of plants seen as beautiful shrubs, which are profusely covered by flowers at the time of blossom. All prefer dry and sunny habitats grow well on poor soils and many of them are commonly cultivated in our gardens.

Winter hardy varieties of Helianthemums are sometimes known as Frostworts, Frostweeds, or Frostplants because their silver foliage makes them look frosted and they retain their good looks even during the winter months.
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Helianthemum nummularium:
Commonly described as a spreading semi-evergreen shrub up-to 30cm (12inches) in height, the leaves originally existed green above and grey underneath. Clusters of bright yellow, saucer shaped flowers would cover the plant in mid-summer. In the centre of the flower is a tight cluster of orange stamens, which are sensitive to touch and spread outwards to reveal the tall stigma in the middle. The plant is common on chalk down land and occasionally on other meadow land, hardy to -20 degrees F.
Over many years, the original Helianthemum nummularium has been cultivated to develop many garden cultivars with flowers ranging from white through yellow to deep red. Further progress in breeding has resulted in the addition of both semi-double and double flowers in many colours. There are now over 200 established named garden cultivars, over 100 of these named cultivars are currently held in my collection.

Cultivation:
The parent plant, Helianthemum nummularium of which many cultivars have been breed is commonly found situated on chalk down land or in meadows. Plants will grow best if you are able to reproduce the same conditions within your garden including bright sunshine, good ventilation and a well-drained slightly alkaline soil. Depending on the individual cultivar, Helianthemum’s can spread up-to 18inches (48cm) and grow to 12in (30cm) in height. In order to produce plenty of flowers, plants should be regularly pruned to encourage fresh growth.

Pruning: Plants should be pruned immediately after summer flowering to help keep them neat and long lived encouraging new growth and another later display of blossom. At the end of the summer flowering, the plants look tired and straggly. Using a sharp pair of secateurs, cut back all the dead flower stems and cut into a round shape, cutting into some of the fresher growth to encourage new shoots. Try not to cut too far into the old wood; this could cause lack of growth.

Once pruning is complete, remove all off cuts helping to ensure the bed is continuously tidy. Remove any weeds, mulch with compost to retain moisture and feed the new growth. If you are self-sufficient, use well-rotted garden compost. Well-rotted manure could be used as an alternative but try to avoid using bark chippings as these will make the soil more acidic. Helianthemum cultivars grow best in a chalk based, slightly alkaline soil.

Plants should be well watered after mulching to encourage fresh foliage.

When propagating new plants, the tips of fresh shoots should be regularly pinched out to encourage growth of a more bushy plant. Without this, plants could become quite straggly.

Flowers commonly have 5 sepals and 5 petals with a centre containing numerous stamens. Each bloom is ephemeral lasting only one day. However, they produce so many buds that each plant will be covered in heavy blooms from May to July. Some of the flowers are bicoloured with a brighter colour centre to attract pollinating insects. It is also common for flowers to fade in colour over a period of time.

The majority of cultivars will tolerate dryness but cannot survive in water logged conditions. Nevertheless, they do need some water on extremely hot, dry days particularly during the hottest days of summer.

Wildlife Benefits:
During the summer months, the plants can be covered with bees and butterflies as Helianthemum’s provide a very good source of nectar. There are several species of small beetles that feed on the foliage. They are also food for the Brown Argus and Green Hairstreak Butterfly caterpillars and the Wood Tiger Month caterpillar.

Medicinal Benefits:
Helianthemum nummularium together to other species of Helianthemum have been grown in cottage gardens for medicinal purposes for over many hundreds of years. They contain labdanum, which can be used to treat ailments such as bronchitis and dysentery. In addition, they can be used in perfumes and as an incense fumigant.

Propagation:
At present there are over 200 named cultivars of Helianthemum nummularium available for sale, some more widely available than others.To maintain this wide selection, cultivars need to be continuously propagated using one of the included propagation methods, either from seed or by cuttings. Propagating from cuttings ensures an exact copy of the parent plant is maintained. Plants from seeds can produce some very interesting forms due to cross pollination.

The majority of Helianthemum’s are propagated from cuttings as this is the quickest, easiest and method with the highest success rate to produce new young plants. With propagating from seeds, germination rate tends to be low and seeds, particularly with Helianthemum cultivars are difficult to collect. Despite not collecting any seeds formally, we have found some self-seeded unique plants produced through cross pollination.
The only true method of propagation for named cultivars is by taking cuttings from existing stock plants with known names. Cuttings are taken any time after flowering, usually throughout the late summer months. The plants are prepared by giving them a good prune once flowering has finished encouraging fresh growth remembering to water regularly in dry conditions. Approximately two inch cuttings are taken from this new growth.
....use a mixture of 2 parts John Innes, 2 parts peat and 1 part sharp sand. ....cut a section of non-flowering, fresh foliage of two to three inches in length from the plant using a knife. Take your cut just below a leaf for optimum rooting... Place the cuttings in a well-lit but shady position out of direct sunlight. Ensure the soil remains damp throughout the rooting process. .... The majority of successful cuttings will be well rooted and ready for transplanting within roughly 6 months. Generally cuttings taken late summer are ready for potting up the following spring. Before considering transplanting, ensure fully rooted - i.e. roots coming through the bottom of the pot. It is common for some cultivars to root more quickly than others and also some are more difficult to grow.

Once rooted, pots of cuttings are carefully separated into individuals and then replanted one to a pot (7cm pot) using the same soil mixture of 2 parts John Innes, 2 parts peat and 1 part sharp sand. To replicate their normal growing conditions on chalk land, I also add a small amount of lime pellets to the soil mixture. Water potted plants regularly in dry weather for optimal growth.

[Source: www.helianthemums.co.uk]

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