Colenso's Speargrass

From Seed

Growing Aciphylla colensoi from seed is a test of patience. Germination is often low and can be very slow, sometimes taking up to 18 months. Use only fresh seed collected in late summer.

Sow into a tray of very gritty compost-a mix of 50/50 sharp sand and peat-free compost is ideal. Cover with a layer of grit. The seeds likely require a period of cold stratification to simulate a winter dormancy before they will sprout. You can achieve this by placing the sown tray in a refrigerator for 4-6 weeks, or simply by leaving the tray outdoors in a protected spot over winter.

Keep the seed tray moist but never saturated. Once seedlings appear, they are slow-growing. Prick them out into deep 'long tom' pots to accommodate their developing taproots without checking their growth. Grow them on for at least two years before planting out into the garden.

From Division

For established clumps, division is the most reliable method of propagation, though it is physically demanding. Aciphylla colensoi forms large, multi-crowned clumps over time. Division is best undertaken in early spring or late autumn.

You will need thick gloves and protective clothing! Lift the clump carefully to preserve as much of the root system as possible. Using a sharp spade or a strong knife, separate the rosettes, ensuring each division has a solid piece of root attached. Older, woody parts of the rhizome should be discarded.

Plant the divisions immediately. If the roots were damaged during separation, trim the foliage back slightly to reduce water loss while the plant re-establishes. Water well initially, but ensure the soil is extremely free-draining to prevent the onset of rot in the wounded rootstock.

Cultivation Notes

Aciphylla colensoi is a plant of the montane and subalpine zones, accustomed to high light, strong winds, and cool temperatures. In the garden, it requires an open, sunny position. It will not tolerate shade or competition from overcrowding plants.

Soil preparation is key: incorporate plenty of grit, gravel, or sharp sand to ensure drainage is instantaneous. While it tolerates dry conditions once established, it appreciates a "cool root run"-moisture deep down in the soil that is accessible to its taproot. A mulch of stones or gravel helps achieve this while keeping the crown dry. It is generally very hardy to frost and snow, making it an excellent architectural plant for rock gardens in colder regions.