Arbutus unedo (strawberry tree, occasionally cane apple) is an evergreen shrub or small tree in the family Ericaceae, native to the Mediterranean region and western Europe north to western France and Ireland. Due to its presence in southwest and northwest Ireland, it is known as either “Irish strawberry tree” or sometimes “Killarney strawberry tree”.
Common in London gardens as it is generally a small tree and survives unattended in our city climate. The Strawberry-tree (Arbutus unedo) grows well in London’s cool wet summers. Pruning is normally a crown raise as the tree is generally small.
Arbutus unedo was one of the many species described by Carl Linnaeus in Volume One of his landmark 1753 work Species Plantarum, giving it the name it still bears today.
A study published in 2001 which analysed ribosomal DNA from Arbutus and related genera found Arbutus to be paraphyletic, and A. unedo to be closely related to the other Mediterranean Basin species such as A. andrachne and A. canariensis and not to the western North American members of the genus.
Arbutus unedo and A. andrachne hybridise naturally where their ranges overlap; the hybrid has been named Arbutus × andrachnoides (syn. A. × hybrida, or A. andrachne × unedo), inheriting traits of both parent species, though fruits are not usually borne freely, and as a hybrid is unlikely to breed true from seed.
Arbutus unedo grows to 5–10 m tall, rarely up to 15 m, with a trunk diameter of up to 80 cm. Zone: 7–10
The leaves are dark green and glossy, 5–10 cm (2–4 in) long and 2–3 cm (0.8–1.2 in) broad, with a serrated margin.The hermaphrodite flowers are white (rarely pale pink), bell-shaped, 4–6 mm diameter, produced panicles of 10–30 together in autumn. They are pollinated by bees. The fruit is a red berry, 1–2 cm diameter, with a rough surface, maturing 12 months at the same time as the next flowering. It is edible, though many people find it bland and meally and tasteless. The name unedo is attributed to Pliny the Elder, who allegedly claimed that “unum tantum edo“, meaning “I eat only one”.
It grows well in London’s cool wet summers.
Arbutus unedo is cultivated as an ornamental plant by plant nurseries. It is used as a single or multi-trunked ornamental tree, and as a specimen or hedge shrub in gardens and public landscapes. When grown as a tree rather than a shrub, basal sprouts are kept pruned off. The plant prefers well-drained soils, and low to moderate soil moisture.
Unlike most of the Ericaceae, A. unedo grows well in basic (limy) pH soils. In cold climates it prefers a sheltered position due to its late flowering habit.
Edward Step, F.L.S the English horticulturalist had this to say about the Strawberry tree.
Not in the woods or by waysides in Great Britain will the Strawberry-tree be found, though it may be seen in parks and gardens; but in parts of the Emerald Isle it is native. Killarney, Muckross, and Bantry are given by Hooker as its Irish stations, but we have also found it in the woods at Woodstock, Co. Kilkenny, in a situation where it seemed unlikely such a tree would be planted. It does not attain a large size—ordinarily about ten or twelve feet—though in cultivation it may attain to twenty or even thirty feet. The bark is rough and scaly, tinged with red, and twisted. The leathery leaves are more or less oval, two or three inches long, with toothed edges and hairy stalks. Although arranged alternately on the shoots, they present the appearance at a little distance of being clustered, rosette fashion, at the tips of the twigs. The creamy-white flowers are clustered in drooping racemes at the ends of the twigs, and are about one-third of an inch across, bell-shaped. When the seed-eggs have been fertilized the corollas drop off, so that in the flowering season (September and October) the ground beneath will usually be found strewn with them. The fruit is a round berry, of an orange-red hue, whose surface is completely studded with little points. As these berries do not come to maturity until about fourteen months after the flowers have dropped their corollas, we may see both flowers and almost full-formed fruit on the tree at the same time. They are not eatable until quite ripe, and even then they are not to everybody’s taste, on account of their austerity. In truth, we have it on the testimony of Pliny that the old Latin name unedo, now enshrined in the specific scientific name, was given to it because to eat one of these tree strawberries was a sufficiently extensive acquaintance for most persons.
It is perhaps unnecessary to add that, in spite of the name, there is no relationship existing between this tree and the Strawberry; nor is there more than a faint superficial resemblance between the fruits of the two plants. The Strawberry belongs to the great Rose family, whilst the nearest British connections of the Arbutus are the Bilberries and Heaths.
Wikipedia has this to say about the history of the Strawberry tree in gardens.
The first signs of its importation into northern European gardens was to 16th-century England from Ireland. In 1586 a correspondent in Ireland sent plants to the Elizabethan courtiers Lord Leicester and Sir Francis Walsingham. An earlier description by Rev. William Turner (The Names of Herbes, 1548) was probably based on hearsay. The Irish association of Arbutus in English gardens is reflected in the inventory taken in 1649 of Henrietta Maria’s Wimbledon: “one very fayre tree, called the Irish arbutis standing in the midle parte of the sayd kitchin garden, very lovely to look upon” By the 18th century Arbutus unedo was well known enough in English gardens for Batty Langley to make the bold and impractical suggestion that it might be used for hedges, though it “will not admit of being clipped as other evergreens are.”
The form A. unedo f. rubra and the hybrid A. × andrachnoides, have gained the Royal Horticultural Society’s Award of Garden Merit.
Outside of London in the UK the gardens at Dunster Castle include the National Plant Collection of Strawberry Trees—A. unedo. During the early 1980s the steep banks on the south side of the castle were planted with over four hundred specimens. With the nine cultivars that were acquired at a later date, this constitutes the “National Arbutus Collection”.
The genus arbutus consists of at least 14 different species of flowering plants and is listed in our flowering trees & shrubs section under Arbutus.
The following arbutus species class as hardy ornamentals suitable for London gardens, being not only listed by horticulturalists such as Angus Duncan Webster in his Hardy Ornamental Flowering Trees and Shrubs. But also because of their longevity of growing in our climate. The date being the earliest record of the species introduction to Britain according to Webster.
ARBUTUS ANDRACHNE.—Levant, 1724. This Mediterranean species is of stout growth, with narrow Laurel-like leaves, reddish deciduous bark, and greenish-white flowers that are produced freely in May. A hybrid form, said to have originated between this species and A. Unedo, partakes in part of the nature of both shrubs, but the flowers are larger than those of A. Unedo.
A. MENZIESII (syn A. procera).—Tall Strawberry Tree. North-west America, 1827. This is hardy in many parts of these islands, particularly maritime districts, and is worthy of culture if only for the large racemose panicles of deliciously-scented white flowers, and peculiar metallic-green leaves. The fruit is orange-red, and only about half the size of those of our commonly cultivated species.
A. UNEDO.—Strawberry Tree. Ireland. This is a beautiful evergreen shrub or small-growing tree, sometimes fully 20 feet high, with ovate-lanceolate leaves, and clusters of pure white or yellowish-tinged flowers appearing in September and October. The bright scarlet fruit, about the size of and resembling a Strawberry, is highly ornamental, and when borne in quantity imparts to the plant an unusual and very attractive appearance. Generally speaking, the Arbutus is hardy, although in inland situations it is sometimes killed to the ground in severe winters, but, springing freely from the root, the plant soon becomes re-established. In a young state it suffers too, but after becoming established and a few feet high, the chances of injury are greatly minimised. Three well-marked varieties are A. Unedo coccinea and A. Unedo rubra, bearing scarlet and deep-red flowers, and A. Unedo microphylla, with much smaller leaves than those of the parent plant.
A. UNEDO CROOMEI differs considerably from the former, in having larger foliage, larger clusters of reddish-pink flowers, and the bark of the young shoots of an enticing ruddy, or rather brownish-red colour. It is a very desirable and highly ornamental plant, and one that is well worthy of extended culture.
There are several others, to wit A. photiniaefolia, A. Rollissoni, A. Millerii, with large leaves, and pretty pink flowers, and A. serratifolia, having deeply serrated leaves. Deep, light loam, if on chalk all the better, and a fairly warm and sheltered situation, would seem to suit the Arbutus best.