Osmanthus - Growing Guide

Sweet olive

Osmanthus are excellent hardy small trees and shrubs for the woodland garden. Those species which have less attractive and plentiful flowers make up for it with interesting and diverse new growth and coloured holly-like foliage. They all have thick leathery leaves and most have holly like spines in one form or another on or at the end of their leaves. Some forms are easier to identify than others which can look a bit similar until they actually flower. While they are not actually windbreak evergreen shrubs they can be used in larger woodland plantings to protect more tender plants in their lee. They can certainly take the wind as well.

The only species which we sadly offer only occasionally is O. fragrans which we found was just too tender for anywhere but a large greenhouse. At Tregrehan Garden they grow O. fragrans f. aurantiacus which has highly fragrant tubular clusters of orange flowers in profusion in the autumn where it grows to 15ft or more in height. A magnificent plant!

I have listed these species of Osmanthus in accordance with my own personal view of their attractiveness and beauty in the gardens here:

O. delavayi from China is one of the harbingers of spring in Cornwall, and the first species to flower here when it only has the camellias and early magnolias to compete with. It starts out as a small, and remains for quite a time, as a rounded bush with small toothed dark green leaves but it will grow, in maturity, to 20ft or so here after 60 to 80 years. The flowers are white and highly fragrant. They literally cover the bush. The clusters of flowers show up well in front of the darker leaves and this is a fine plant for the smaller garden.

O. decorus (syn. Phillyrea decora) flowers a bit later in March or April. It is a more vigorous dense, rounded, spreading shrub with much larger oval or oblong pointed leathery leaves. It grows to around 15ft eventually with a greater spread than this. The tubular white flowers are produced in dense clusters. This is an eastern European species.

O. yunnanensis grows with us in maturity as a tree of 40ft or more with a huge trunk after 100 or so years. After a more reasonable 25 years it is a dense bush of 10-12ft in height with obovate leaves which are more spiny or toothed in younger plants. The flowers appear in Cornwall before Christmas and are creamy-white with great fragrance. Sadly our old specimen tree is dying but youngsters are coming on nicely.

Then we come to two hybrids which are direct crosses between four of the five species mentioned in this article. You now see the identification issues looking only at their leaves!

O. x burkwoodii is O. decorus x O. delavayi. It is an excellent plant with the vigour and the best attributes of both its parent species. It grows to 15ft or so eventually and has very scented tubular white flowers in mid to late spring. It sells better than O. delavayi but it ought not to!

O. x fortunei is a cross between O. fragrans and O. heterophyllus. This is an upright shrub maturing to a height of 15-20ft with the holly-like leaves you would expect from O. heterophyllus, and the smaller, very fragrant, white tubular flower clusters you would expect from O. fragrans. It is, however, perfectly hardy and we grow it in the teeth of the wind. The great attribute that it takes from O. heterophyllus is the gorgeous purple new growth colours which it has in late spring.

O. heterophyllus is fairly dull by comparison at least as far as its flowers are concerned. Again the reference books say it is a smallish, rounded shrub but some of the original plants here grown from Chinese collected seed 100 years ago are now actually rounded trees. They, however, grow slowly so there is no real need to worry about space in the garden. This is perhaps a plant which could be used as a windbreak, as we do, but it would perhaps make a clipped hedge if you had the time and energy to prune it regularly.

This evergreen has holly like leaves with sharply toothed, leathery and very glossy dark green leaves. It flowers in late summer or autumn but, sadly, hardly ever gets noticed. Again the flowers are tubular and scented in clusters.

There are three other forms of O. heterophyllus which the nursery stocks which are probably more interesting woodland garden plants:

‘Aureomarginatus’ has golden edged foliage and grows with us to 20ft after 30 years.

‘Goshiki’ grows to only 6-8ft and has speckled gold and white foliage with cream and pink on the young foliage.

‘Purpureus’ has exceptional young purple new growth.

‘Variegatus’ – this is a plant that looks like a holly but is not! The silver edged foliage shows up well in a shady corner.

All forms of O. heterophyllus are perfectly happy in partial shade but the coloured foliage forms need more sun to get their best colours.