Bewitchingly beautiful

Cupressus macrocarpa, Greenstead Magnificent, at the Botanic Garden, Dunedin.  Photo by Linda...
Cupressus macrocarpa, Greenstead Magnificent, at the Botanic Garden, Dunedin. Photo by Linda Robertson.
One of the newest areas on the rock garden is the dwarf conifer cultivar collection.

The first plantings took place in 2001 and further developments are planned to expand this diverse collection.

The plantings include a wide variety of species, incorporating an extensive range of colours, textures and shapes.

Many of these cultivars began their lives as a witches broom growth on a mature tree.

Bewitched

Sometimes when damage occurs on a woody plant it can cause a deformity where the natural structure of the plant is altered, resulting in a dense mass of shoots arising from a single point.

This resembles a witches broom and may be caused by a pest or disease, mechanical damage, or occasionally by genetic mutation in the growth bud.

It is the latter that nurserymen are interested in.

Cuttings or seed collected off this genetically unique material form slower growing and more compact versions of the parent plant that are often very desirable.

Hard graft

As the collected material can be weaker growing than the parent, it is often grafted on to a stronger rootstock.

The scion (upper part with desirable features), is attached to a seedling of the parent or a very closely related species.

Once this graft has taken, the top of the seedling is removed, allowing the conifer cultivar to grow on the tougher rootstock.

'Cupressus macrocarpa' - Greenstead Magnificent

One such plant in the collection was discovered as a blue witches broom on a mature specimen of the Monterey cypress or macrocarpa, Cupressus macrocarpa.

The parent plant is dark green, and has the potential to reach heights of up to 45m, whereas the cultivar Greenstead Magnificent forms a low, dense and spreading blue-grey shrub.

It has an attractive weeping habit and can be grafted as a ground cover or on a metre-high standard, forming an upside-down umbrella.

Like most dwarf conifers, it is slow growing, taking 10 years to reach around 1m high with a spread of 5m.

- Robyn Freeth is the rock, water and alpine collection curator at the Dunedin Botanic Garden.

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