Cannomois grandis is one of the few species of Cannamois that is easy to grow from seed. Fresh seed, i.e. up to a year old, is smoked in late summer or autumn using old or semi-green, fynbos or smoke extract. In other regions it should probably be germinated at the beginning of the growing season. Treatment with smoke or smoke extract greatly enhances germination, where up to 70% has been regularly achieved. Germination diminishes the older the seed gets. The seed takes about 6 to 10 weeks to germinate. The young seedlings should be protected from heavy rainfall and direct sunlight, by placing the trays under cover while still providing good light and aeration. Allow the young plants to grow to about 10 mm tall before planting them out into multi-trays or small pots or bags. Plants should be grown up to at least 300 mm high, before planting out in the garden.

It can also be propagated by division in winter. Dig up mature plants and divide the rhizomes into large chunks. Remove the ‘leafy’ culm growth. Plant into well-drained soil and keep moist. Treatment with a seaweed extract once a month will encourage new root and shoot growth in spring, once the weather warms up.

It is generally found in dampish soils or seeps, so it is important to keep this plant moist during the summer. Apply additional water in areas where the winters are dry.

It should do well in most gardens in South Africa where the humidity is not too high and where there is little or no frost. They should do well in coastal gardens as long as the soils are acidic and they are not exposed to direct salt-laden wind. It grows well in various garden aspects, including open beds, rockeries and on slopes.

Feed before flowering with slow release 3:1:5 or monthly with a good organic seaweed-derived fertilizer. Be careful not to disturb the roots and water regularly, as summer drought is generally the cause of losses. Good results have also been achieved when applying controlled release fertilizers suitable for fynbos. Be careful not to exceed dosage. Use liberal amounts of compost to improve the soil. You can also apply an organic fertilizer low in phosphates twice a year for lush green growth, although this is not essential. Cannomois grandis is generally free from pests and diseases.

Plant Cannomois grandis in a sunny position in well-drained soil and water regularly. Plants require a large area to grow because of its size. Tidy up plants by removing straggly and dead culms as they appear. If plants are looking old and tired, stimulate new growth by cutting the culms down to the ground in late autumn. This emulates what a fire would do in nature.

Cannomois grandis is suited to an informal garden style where the branching willowy culms will create texture and movement in the garden. Combine it with sturdy plants that will be able to grow above and through the spreading rhizomes. A few examples of planting companions are Agathosma ovata, Watsonia borbonica, Berzelia abrotanoides, Protea repens, Leucospermum cordifolium, Podalyria calyptrata and Erica scabruiscula.

It is grown overseas where it is reported to tolerate temperatures down to -6ºC. Give it a good organic mulch in late autumn to protect it over the winter.