Euphorbia altissima (tall spurge) — Clump-forming, upright or spreading sub-shrub

Overview

Euphorbia altissima is a clump-forming, upright or spreading sub-shrub perennial in the genus Euphorbia, part of the Euphorbiaceae family, with evergreen, semi-evergreen or deciduous; narrow, often blue-grey or glaucous, sometimes red-tinted in autumn foliage. Euphorbia altissima grows best in full sun to partial shade; the woodland species tolerate dry shade, and tolerates light to moderately fertile loam and sand or chalk soils and acid and neutral or alkaline pH. Its UK hardiness is rated H4-H7. Suggested uses include borders, wild gardens and naturalized areas. It is native to South Africa.

About

Euphorbia altissima is a clump-forming perennial spurge with an upright to spreading sub-shrub habit and narrow, often glaucous leaves. Foliage can be evergreen, semi-evergreen or deciduous, sometimes taking a red tint in autumn. It flowers from May to September and suits well-drained soils on loam, sand or chalk. The milky sap is a skin and eye irritant, so wear gloves when handling.

About the genus

Euphorbia is a large and diverse genus of flowering plants, commonly called spurge, in the family Euphorbiaceae.

Wikipedia contributors, "Euphorbia", CC BY-SA 4.0 — Euphorbia

In the garden

Euphorbia altissima comes from South Africa and grows as a clump-forming, upright or spreading sub-shrub with narrow, often blue-grey (glaucous) leaves that may redden in autumn. It produces its flowers between May and September and can behave as evergreen, semi-evergreen or deciduous depending on site and winter severity. Plant it where it receives full sun to partial shade; woodland forms will tolerate dry shade. It prefers light to moderately fertile loam, sand or chalk and dislikes winter wet, so free-draining soil is essential. Aspect can be any and it will cope in both exposed and sheltered positions. Hardiness ranges from H4 to H7 (average to fully hardy), so it will survive typical UK winters provided crowns are not waterlogged. Use tall spurge in mixed borders, wild or naturalised areas and sunny gravelly corners where its glaucous foliage provides structure through the year. Give a sheltered hole of gritty mix if your soil is heavy clay, and avoid low-lying wet spots. Take care when pruning or cutting seedheads: the milky sap can irritate skin and eyes and contact should be avoided during late-summer work.

Growing conditions

Best soil and position for Euphorbia

Sunlight: Full sun to partial shade; the woodland species tolerate dry shade
Soil type: Light to moderately fertile loam, sand or chalk
Soil pH: Acid, neutral or alkaline
Soil moisture: Well drained; most dislike winter wet
Aspect: Any
Exposure: Exposed or sheltered
UK hardiness: H4-H7

Plant details

Euphorbia altissima size, habit and characteristics

Plant type: Perennial
Habit: Clump-forming, upright or spreading sub-shrub
Foliage: Evergreen, semi-evergreen or deciduous; narrow, often blue-grey or glaucous, sometimes red-tinted in autumn
Suggested uses: Borders, wild gardens, naturalized areas
Native to: South Africa
Toxicity: The milky sap is a skin and eye irritant

Care notes

Pruning and caring for Euphorbia altissima

Cultivation: Easy and largely self-sufficient given drainage. The milky sap is a genuine irritant to skin and eyes, so wear gloves and eye protection when cutting back and never handle the plant in strong sun. Most flower on stems produced the previous year, which makes correct timing of the cut essential. The spreading species can be invasive in loose soil, so site them accordingly.
Pruning: On the shrubby evergreen kinds, cut flowered stems right to the base once the bracts fade in summer, leaving this season's new shoots to flower next year. Cut herbaceous species down in late autumn.
Propagation: Divide herbaceous kinds in spring. Take basal cuttings of shrubby species in spring and rinse the cut end to stop the latex sealing it. Many self-seed freely.
Pest resistance: Rarely troubled by pests; aphids occasionally gather on soft new growth.
Disease resistance: Generally healthy. Euphorbia rust causes orange spotting and distorted shoots on some species and affected growth should be removed.

Frequently asked questions

How do I grow Euphorbia altissima?

Easy and largely self-sufficient given drainage. The milky sap is a genuine irritant to skin and eyes, so wear gloves and eye protection when cutting back and never handle the plant in strong sun. Most flower on stems produced the previous year, which makes correct timing of the cut essential. The spreading species can be invasive in loose soil, so site them accordingly.

Where is the best place to plant Euphorbia altissima?

Euphorbia altissima prefers full sun to partial shade; the woodland species tolerate dry shade. It suits exposed or sheltered positions.

What soil does Euphorbia altissima need?

Euphorbia altissima grows best in light to moderately fertile loam and sand or chalk soil. It prefers acid and neutral or alkaline soil. Aim for soil that stays well drained; most dislike winter wet.

How do I prune Euphorbia altissima?

On the shrubby evergreen kinds, cut flowered stems right to the base once the bracts fade in summer, leaving this season's new shoots to flower next year. Cut herbaceous species down in late autumn.

Is Euphorbia altissima hardy in the UK?

Euphorbia altissima has an RHS hardiness rating of H4, meaning it is hardy through an average UK winter, tolerating -10 to -5°C.

How do I propagate Euphorbia altissima?

Divide herbaceous kinds in spring. Take basal cuttings of shrubby species in spring and rinse the cut end to stop the latex sealing it. Many self-seed freely.

Is Euphorbia altissima toxic?

The milky sap is a skin and eye irritant.

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