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White Milkwood

Sideroxylon inerma

SA tree no: 579

English: White Milkwood, Milkwood, Sea Milkwood

Afrikaans: Witmelkhout, Melkhoutboom, Melkbessie

Xhosa: aMasethole, umQwashu

Zulu: aMasethole-amhlope, uMakhwela-fingqane

Venda: Mutaladzi-vhufa

Historical scientific names: Calvaria inermis, Sideroxylon atrovirens, Sideroxylon inerme var. schlechteri

Sideroxylon inerme, commonly known as White Milkwood or Witmelkhout, is an iconic indigenous evergreen tree found extensively along the South African coastline and into inland forest patches. It is a highly revered species, known for its dense, rounded crown of glossy dark green leaves, a characteristic milky white latex that oozes from damaged parts, and its small, purplish-black fruits. As a protected tree in South Africa, the White Milkwood is celebrated not only for its resilience in harsh coastal environments, providing essential windbreak and dune stabilisation, but also for its profound historical significance.

White Milkwood (Sideroxylon inerma)
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Distinguishing features:

A medium-sized evergreen tree with a dense, rounded, and often gnarled crown.
Features thick, leathery, glossy dark green leaves with a paler underside, sometimes with rusty hairs when young.
Produces milky white latex when any part of the plant is cut or bruised.
Bears small, inconspicuous, greenish-white flowers with a strong, often unpleasant smell.
Develops small, fleshy, spherical fruits that ripen to purplish-black.
Extremely hardy and tolerant of coastal conditions, wind, and drought.
Protected tree in South Africa, meaning permits are required for damage or removal.

Overall appearance:

Sideroxylon inerme typically forms a sturdy, often multi-stemmed tree with a characteristic gnarled trunk and a dense, rounded crown that casts significant shade. Its lush, glossy green foliage gives it a robust, established appearance, and while its flowers are small, the ensuing abundance of purplish-black berries adds subtle seasonal interest.

Height:

Typically grows 4 to 15 metres tall, but can sometimes be a smaller, multi-stemmed shrub in exposed coastal areas or grow taller in sheltered forest environments.

Width:

Forms a broad, spreading crown, usually 5 to 10 metres wide.

Leaves:

Simple, alternate, or sometimes clustered at the ends of branches.
Shape is typically elliptic to obovate (spoon-shaped) or ovate, 3–12 cm long and 1.5–6 cm wide.
They are thick, leathery (coriaceous), glossy dark green on the upper surface, paler green beneath.
Margins are entire (smooth).
Young leaves may have a reddish or rusty tinge and sometimes fine hairs that rub off with age.
When broken, the leaves and stems exude a characteristic milky white latex.

Flowers:

Tiny, inconspicuous, 5-petalled, greenish-white to yellowish.
Borne in small, dense clusters (axillary fascicles) in the leaf axils.
Possess a strong, somewhat fetid (unpleasant) fragrance, especially noticeable up close.

Flowering season:

Flowers primarily in late summer to autumn, typically from November to April, but can flower sporadically.

Fruits:

Small, spherical, fleshy berries (drupes), about 8–12 mm in diameter.
Initially green, ripening to a distinctive purplish-black when mature.
Smooth-skinned and juicy, containing a milky latex.
Borne solitarily or in small clusters.
Persist on the plant for many months, providing a long-lasting food source for birds.

Seeds:

Typically one, large, hard, shiny brown to black, ovoid seed enclosed within the fleshy fruit.

Bark:

Smooth and greyish-brown on younger stems, becoming thicker, darker grey to almost black, and characteristically fissured into rectangles or squares with age.

Stems:

Often thick, gnarled, and twisted, especially in exposed coastal conditions. Young branches can be covered with fine, soft, grey or rusty hairs. Exudes milky latex when damaged.

Wood:

The wood is extremely hard, heavy, and strong, hence the "ironwood" part of its Greek scientific name. Historically used for shipbuilding, bridges, mills, and various implements due to its durability.

Thorns:

This tree is thornless.

Roots:

Possesses a strong, extensive root system that effectively anchors it in sandy and coastal soils, playing a crucial role in dune stabilisation. Generally non-invasive in garden settings.

Soil type:

Highly adaptable to a wide range of well-drained soils, including sandy, loamy, and even rocky soils. It thrives in coastal soils but also grows well in inland areas with sufficient moisture. It tolerates poor soil fertility.

Aspect:

Thrives in full sun but can tolerate semi-shade. It is extremely hardy to wind, salt spray, and drought once established. It is moderately frost-hardy, tolerating light to moderate frost, though severe frost can cause some defoliation or damage to young plants.

Edibility:

The fruits are edible for humans, tasting somewhat like a grape once peeled of their outer skin. They contain a milky latex.

Toxicity:

Considered non-toxic. The fruits are edible, and extracts from the bark and roots have traditional medicinal uses.

Uses:

Ornamental Tree: A highly valued ornamental tree, particularly for coastal gardens, due to its attractive dense crown, glossy foliage, and hardiness. Provides excellent shade.
Coastal Stabilisation: Crucial for stabilising coastal dunes and preventing erosion due to its robust root system and wind tolerance. Often forms dense thickets in dune forests.
Wildlife Garden: The fruits are a major food source for a wide variety of fruit-eating birds (e.g., Red-winged Starlings, Cape White-eyes, turacos, bulbuls) and other wildlife (e.g., monkeys, bushbuck). The dense canopy provides nesting sites and shelter.
Historical Significance: Several individual White Milkwood trees in South Africa have been declared National Monuments due to their exceptional age and historical importance (e.g., the Post Office Tree in Mossel Bay, the Treaty Tree in Woodstock, Cape Town, and the Fingo Milkwood Tree near Peddie, Eastern Cape).
Traditional Medicine: The bark and roots have been traditionally used in various medicinal preparations for ailments such as broken bones, fevers, and to dispel nightmares.
Firebreak: Due to its dense, evergreen foliage and resilient nature, it can act as an effective firebreak.
Bonsai Subject: Its gnarled trunk and dense foliage make it a good subject for bonsai cultivation.

Ecology:

Pollination: The flowers, despite their inconspicuous appearance, attract insects, including bees, for pollination.
Seed Dispersal: The fleshy fruits are a highly sought-after food source for numerous bird species, bats, monkeys, and other small mammals, which are the primary dispersers of the seeds (endozoochory).
Habitat Provision: Provides vital shelter, shade, and nesting sites for a wide range of coastal fauna due to its dense canopy. It is a keystone species in many coastal dune forest ecosystems.
Host Plant: Larval host plant for the Pallid Emperor moth (Cirina forda).

Distribution and habitat:

Sideroxylon inerme is widely distributed along the southern and eastern coastline of South Africa, extending northwards into tropical Africa.

South African Provinces: Western Cape, Eastern Cape, KwaZulu-Natal, Mpumalanga, Limpopo. Also found in Swaziland, Mozambique, Zimbabwe, and further north.
Habitat: Primarily found in coastal dune forests, evergreen forests, coastal bushveld, and along riverbanks near the coast. It is particularly characteristic of the transition zone between dunes and inland vegetation. It can form dense, almost impenetrable thickets.

Derivation of name:

The genus name Sideroxylon is derived from the Greek words 'sideros' meaning "iron," and 'xylon' meaning "wood," referring to the exceptionally hard and dense wood of this tree.
The species epithet inerme is Latin for "unarmed" or "without thorns," referring to the lack of thorns, which distinguishes it from many other thorny coastal species.
The common names "White Milkwood" and "Witmelkhout" refer to the milky white latex that oozes from its bark and leaves when damaged.

Historical aspects:

The White Milkwood holds immense historical and cultural significance in South Africa. Its remarkable longevity means that individual trees have witnessed centuries of history. Three specimens have been declared National Monuments: the Post Office Tree in Mossel Bay (where a Portuguese explorer left a letter in 1500), the Treaty Tree in Woodstock (where the Cape was formally handed over to the British in 1806), and the Fingo Milkwood Tree near Peddie (where the Fingo people affirmed their loyalty to the British Crown in 1835). This deep historical connection underscores its protected status.

Interesting facts:

The "White Milkwood" is a true living legend in South Africa, with some individual trees being hundreds of years old and even holding National Monument status because of their role in history!
If you scratch its bark or break a leaf, a milky white sap will ooze out, which is where it gets its common name – but don't worry, it's not poisonous!
This amazing tree is a natural superhero for our coastlines; its incredibly strong roots help to hold sandy dunes together, protecting them from erosion by the powerful ocean winds.

Growing tips:

Propagation: Best propagated from fresh seeds. Seeds can be slow to germinate (a few months to over a year) and benefit from cleaning the fleshy pulp off and soaking in warm water for 24 hours. Sow in well-drained, sandy loam. It can also be propagated from large truncheons (thick cuttings) taken in winter, which should be allowed to form a hard layer over the cut ends before planting deeply.
Planting: Prefers a sunny position and well-drained soil. While tolerant of coastal conditions, it benefits from some protection from direct, salt-laden sea winds when young. Allow ample space for its broad, spreading crown.
Watering: Water regularly when young to establish a strong root system. Once established, it is extremely drought-tolerant and requires minimal supplementary watering.
Frost: Moderately frost-hardy. Young plants may need protection from severe frost. Mature trees can withstand light to moderate frost.
Maintenance: Low maintenance. Prune only to shape, remove dead/damaged branches, or to lift the crown for clearance. Remember, it is a protected tree, so any significant trimming or removal requires a permit from the Department of Agriculture, Forestry, and Fisheries.
Pests/Diseases: Generally robust and resistant.