Virgilia oroboidesR Picture courtesy Yellowwood Indigenous Nursery yellowwoodnursery.co.za Condensed Version:

Two popular species of the Keurboom; Virgilia divaricata and Virgillia oroboides are very similar and often confused with each other. Both species are small to medium sized trees with lovely feathery leaves and a rounded to broadly conical growth habit; branching close to the ground. They are very fast growing when young, reaching their full height in only a few years.  V. divaricata grows from 6 to 10m in height, rarely exceeding 10m; while V. oroboides can reach 10 to 15m tall. When the trees are young the bark is smooth and a silver-grey, but with maturity it becomes grey and rough. Both trees produce dense terminal sprays of sweetly scented pea shaped flowers; and can flower sporadically out of season. V. divaricata has violet-pink flowers with dark purple tips and its main flowering season is in spring and early summer; while the blooms of V. oroboides are pinkish-white to white and generally appear in mid to late summer. The flowers are rich in nectar; attracting many insects and birds; and long flat brown seed pods containing follow the flowers. The leaflets of V. oroboides are greyish green in colour and both the leaves and the twigs are densely covered in conspicuous rust-coloured, velvety hairs, whereas those of V. divaricata are green and almost hairless.

A Keurboom is the perfect tree for a new, bare garden because it grows so fast it will take only two or three years before it will be creating shade, or a screen, and filtering the wind—which is an important consideration in Cape Town suburbs. It is also a perfect pioneer species for woodland development where it is planted with slower growing species like milkwoods, providing shade and wind protection for more tender plants.  The popular Keurboom will provide light shade and looks spectacular wherever it is planted, being suitable for both small and large gardens;  in smaller gardens plant Virgilia divaricata because its growth is more compact and it is amazingly beautiful when in full flower. The Keurboom is a wonderful street tree and is often used in office parks and parking lots, or other built up areas where a fast growing shade tree is required. Because it branches low down it makes an ideal screening plant and windbreak.

Although the Keurboom thrives in the winter rainfall regions it can be grown inland if it is watered well in the dry winter months. While mature trees can survive short spells of light frost, young trees must be protected for the first few years. The trees will grow equally well in full sun or semi shade and are adaptable to most light, well drained soils. Although it is able to withstand moderate drought once established, the trees grow best if watered well when young and during prolonged dry spells.

Virgillia divericata Picture courtesy www.newplant.co.zaFull Version:

Description, History & Interesting Facts:

The Keurboom is a beautiful evergreen indigenous flowering tree which belongs to the pea and bean family (Fabaceae) and grows wild in a small, narrow strip along our south-eastern coastline. Two popular species; Virgilia divaricata and Virgillia oroboides are very similar and often confused with each other. Both are commonly found growing alongside streams and river banks; on forest margins, in thickets and on hillsides. Virgilia oroboides occurs below 1 200m along the coast from the Cape Peninsula to George.  V. divaricata is also found below 1 200m, but from the Klein Swartberg Mountains to George, and to Van Staden's Pass near Port Elizabeth in the Eastern Cape. It is abundant in the Knysna and Plettenberg Bay area, and especially along the Keurbooms River, which takes its name from this tree.

Both species are small to medium sized trees with lovely feathery leaves and a rounded to broadly conical growth habit; and branching close to the ground. They are very fast growing when young, reaching their full height in only a few years. V. divaricata grows from 6 to 10m in height, rarely exceeding 10m; while V. oroboides can reach 10 to 15m tall. Because they grow so quickly; they are relatively short lived, with an average lifespan of 15 to 20 years. When the trees are young the bark is smooth and a silver-grey, but with maturity it becomes grey and rough, with a trunk diameter of about to 60cm.

Both trees produce dense terminal sprays of sweetly scented pea shaped flowers; and can flower sporadically out of season. V. divaricata has pinkish-mauve to violet-pink flowers with dark purple tips and its main flowering season is in spring and early summer (August to November); while the blooms of V. oroboides are pale pink or pinkish-white to white and generally appear in mid to late summer (January to April); but trees growing near George have rose-violet or purple-violet flowers which generally appear in spring. The flowers are rich in nectar; attracting many insects and birds, such as sunbirds, carpenter bees, honey bees and ants.  Doves and white-eyes love to nest in the branches, and in the forests the large handsome ghost moth (Leto venus) lays its eggs at the foot of the Keurboom so that the hatching caterpillars can bore into the wood. The Blue Butterfly or Lucerne Blue (Lampides boeticus) is also known to breed on Keurboom trees, as well as Lucerne.  Long flat brown seed pods containing up to 11 seeds follow the flowers; and these are often foraged by livestock and poultry.

Because Keurboom species are so similar it can lead to confusion between; and they are differentiated from each other by their leaves. The leaflets of V. oroboides are greyish green in colour and both the leaves and the twigs are densely covered in conspicuous rust-coloured, velvety hairs, whereas those of V. divaricata are green and almost hairless. Many horticulturalists still disagree as to whether Virgilia is one variable species or two separate species. At present they are regarded as two separate species; with V. oroboides being divided into two subspecies. The tree growing in the George district with its rose-violet-flowers and rust-coloured hairs on the leaves and twigs being classified as V. oroboides subsp. ferruginea; and the pale, pink-flowered plant with white hairs on the leaves and twigs that occurs from the Cape Peninsula to Swellendam being V. oroboides subsp. oroboides.

Uses:

In earlier times the wood was very much in demand and used to make furniture as well as yokes, spars, wagon-bed planks and rafters. The transparent gum that exudes from the bark was also used as a substitute for starch.

In the Garden:

Keurboom trees were cultivated in England as long ago as 1767 and are also grown in Australia and in the USA today, where they are also known as Tree-in-a-hurry or Cape lilac. A Keurboom is the perfect tree for a new, bare garden because it grows so fast it will take only two or three years before it will be creating shade, or a screen, and filtering the wind—which is an important consideration in Cape Town suburbs. It is also a perfect pioneer species for woodland development where it is planted with slower growing species like milkwoods, providing shade and wind protection for more tender plants. Because it sheds small branches and leaves regularly, it also provides valuable mulch for the soil.The popular Keurboom will provide light shade and looks spectacular wherever it is planted, being suitable for both small and large gardens;  in smaller gardens plant Virgilia divaricata because its growth is more compact and it is amazingly beautiful when in full flower. The Keurboom is a wonderful street tree and is often used in office parks and parking lots, or other built up areas where a fast growing shade tree is required. Because it branches low down it makes an ideal screening plant and windbreak.

Cultivation/Propagation:

Although the Keurboom thrives in the winter rainfall regions it can be grown inland if it is watered well in the dry winter months. While mature trees can survive short spells of light frost, young trees must be protected for the first few years. The trees will grow equally well in full sun or semi shade and are adaptable to most light, well drained soils. Although the Keurboom is able to withstand moderate drought once established, the trees grow best if watered well when young and during prolonged dry spells.

Virgilia is easily propagated from seed sown in spring or autumn; but because the seed coat is hard it requires some stimulation to initiate germination. Seeds can be soaked in hot water before sowing, or the seed coat can be cracked artificially. They also respond to stimulation by fire and can be treated with the Kirstenbosch Instant Smoke Plus Seed Primer. Sow in soil which drains well and at a depth of 0.5 to 1cm. Seed can also be sown directly into the ground and because they are highly fertile, can remain alive for up to 30 years. Seedlings can be transplanted after the first true leaves.