New Zealand-bur: complete guide

Overview

New Zealand-bur (Acaena novae-zelandiae) is a low-growing perennial herb native to New Zealand, Australia and surrounding Pacific islands. This herbaceous plant belongs to the Rosaceae family (rose family) and is renowned for its distinctive red spiny fruits and compact, seed-dispersing growth pattern. The plant grows naturally in mountain areas, alpine meadows and rocky coasts of New Zealand at elevations up to 1500 metres.

New Zealand-bur typically reaches only 10 to 20 centimetres in height, forming dense mats or turfs through underground runners. This is an exceptionally valuable plant for those seeking compact groundcovers in dry, alpine environments. The plant is also well-known for its characteristic spiky fruits that are dispersed by animals, especially birds.

Appearance and bloom

New Zealand-bur displays very fine, small leaves in greenish to grey-green colour. The leaves are compound and very densely packed on stems, giving the plant a fine texture. Some cultivars have bronze to reddish-coloured foliage, providing additional visual interest.

Flowers are extremely small (approximately 2-3 millimetres), yellow-green and inconspicuous, appearing in small, compound clusters May-June. These flowers are not spectacular but attract insects. Following pollination, the characteristic fruits develop: small, spherical fruits (approximately 5-8 millimetres diameter) surrounded by stiff red spines.

The red spiny fruits ripen July-August and remain attractive for long periods. These fruits are highly conspicuous against the grey-green foliage and immediately catch the eye of bird enthusiasts. The spines of the fruit hook into animal fur, enabling dispersal.

Ideal location

New Zealand-bur grows best in full sun to half-shade. Ideally, position it where it receives at least 5 to 6 hours of direct sunlight daily. The plant tolerates partial shade but blooms and fruits better in full sun. In very warm climates, some afternoon shade can be beneficial.

Plant this groundcover between rocks in rock gardens, on dry slopes, along borders with other alpine plants, or as floor coverage under small shrubs. New Zealand-bur also works well in wild corners, in balcony planters, and in rock gardens where drought-loving plants are desired.

Soil

New Zealand-bur is very adaptable to different soil types, provided they are well-draining. The plant grows in both acid and neutral to slightly alkaline soils (pH 5.5 to 7.5). This alpine plant tolerates lean, poor soils well, making it exceptionally valuable for rock gardens.

Heavy, moisture-retaining clay soils are less suitable without improved drainage. Add coarse sand, gravel or perlite at the planting hole to improve drainage. The plant grows even in chalky soils without problems. Once established, the plant is very adaptable.

Watering

New Zealand-bur is extremely drought-tolerant once established. Water regularly only during the initial growing phase (April-May). Once actively growing, this plant can survive in dry conditions thanks to its shallow but extensive root system.

During very dry summers, provide occasional water, especially for young plants. But waterlogging is fatal for this plant. In rainy climates, the plant tolerates moist conditions well, as long as drainage is adequate. Monitor moisture carefully in container plants.

Propagation

New Zealand-bur can be grown from seed or easily propagated by detaching underground runners and planting separately. Seed can be sown directly into ground in spring (March-April) or in small pots for further cultivation.

The plant usually spreads via underground runners, so it is easy to collect plant material from established plants. Sever runners and replant separately. The plant grows quickly and makes new plantlets.

Maintenance calendar

January to February: Prepare for growth. Plant new specimens.

March to April: Growth accelerates. Monitor moisture.

April to May: Active growth. Small yellow flowers appear.

May to June: Flowering. Fruit development begins.

July to August: Fruits ripen to red. Very attractive.

September to October: Fruits remain attractive. Plants spread seeds.

November to December: Growth slows. Winter preparation.

Winter hardiness

New Zealand-bur is modestly winter hardy and grows without much difficulty in USDA hardiness zones 7 to 9 (approximately -17 to 0 degrees Celsius in winter extremes). In colder zones (5-6), the plant may struggle in very severe winters but normally regrows in spring.

In zone 4 and colder, plant it in protected locations away from damaging winds, or protect with mulch in winter. In very warm zones (10 and higher), the plant grows better at higher, cooler locations.

Companion plants

New Zealand-bur pairs well with other alpine groundcovers:

• Sedum species (stonecrops)
• Thymus (thyme)
• Saxifraga (saxifrage)
• Draba (draba)
• Armeria (thrift)

Also combine with drought-tolerant grasses for texture.

Final thoughts

New Zealand-bur is a splendid choice for those seeking unique groundcovers with striking fruits. Plant in groups of at least 3-5 for best effect. The plant will slowly expand via underground runners. This is a very interesting, long-lived plant requiring virtually no maintenance.

Specialized nurseries stock young plants of this New Zealand species. Plant in dry locations where other plants struggle. The red spiny fruits attract considerable bird attention and the plant supports local insect populations well.