By Mark Thomas
There is a general belief amongst many home gardeners that yaccas or grasstrees (not to be confused with South American Yuccas) are too slow growing to be a worthwhile garden plant. The species that grow trunks will do so slowly at the rate of about 2-3cm per year; however the skirt of fine foliage will grow much quicker, creating an amazing feature. They belong to the genus Xanthorrhoea in the lily family, with 28 species and 5 subspecies.
The advanced specimens with trunks for sale in nurseries have been taken from bushland interstate, where it is permitted and they may be hundreds of years old. This practice is unsustainable and leaves the customer with a plant that may be slowly dying, although outward signs of poor health may take more than 12 months to show.
Growing yaccas can be easy and rewarding if you follow a few general principles.
- Sunny position for most species, although Xanthorrhoea semiplana does well in strong dappled light and under open canopied trees.
- Drainage should be good and raising plants on a mound will help if you have heavy soils. Add gypsum and dig in compost to your soil when preparing your hole. A good species for clay soils is one of the local species X. quadrangulata (Mount Lofty grass tree).
- pH can be important, particularly if you are growing a species from interstate. If your soil is alkaline and heavy X. quadrangulata (Mount Lofty grass tree) may be your best option.
- Protect small plants from rabbits, kangaroos or trampling with a tree-guard. Tube-stock plants will take about 3-5 years to be a robust plant.
- An open position away from eaves, solid structures and other plants.
- Use a low phosphorous (P) native fertiliser in late winter and early autumn.
Advanced 5 year old plants with a 50-60 cm skirt of foliage can be purchased from several of Adelaide’s specialist native nurseries. The plants are grown in the nursery from seed to a size that suits your needs. 5 year old plants sometimes send up a flower spike while still in the nursery. I had mine at home flower within 18 months of being planted, giving a bonanza of nectar for the native birds.
By Mark Thomas
Every autumn, bulbs begin shooting, sending up delicate foliage and bright flowers en masse before they die back down in the heat of summer. Many gardeners would be surprised to learn there are many species of native bulbs, most of them lilies and easy to grow.
In this alternative method of drought resistance plants producing bulbs avoid the desiccating heat by retreating underground where temperatures remain more stable for summer dormancy. Moisture is conserved inside the bulb and the lack of summer rainfall becomes inconsequential.
Native lilies inhabit most habitats across South Australia, from forests and woodlands to wetlands and mallee. A species that would have been very common over much of southern SA is Arthropodium strictum (chocolate lily/ vanilla lily). Basal rosettes of foliage arising in mid- autumn are followed by flower spikes reaching up to a metre tall in winter. The numerous mauve flowers are sweet scented reminiscent of chocolate or vanilla as the common name suggests, and sometimes last right up to the beginning of the hot weather if there has been good rainfall.
Calostemma purpureum (garland lily) can still be found in many of the areas with reasonable native vegetation. The mass of flowers can be a spectacular sight in years where there has been heavy, late summer rainfall such as this February and accentuated by the lack of other flowers in very early autumn. Red-purple flowers are borne on stalks up to 50cm tall, arriving naked before the foliage, just as their non-native cousin Amaryllis belladonna (Easter lily). The seed of this species is large, up to pea sized and it is not uncommon for the seed to germinate as soon as it has fallen from the flower stalks.
Flowering through late winter to spring is the bright yellow Bulbine bulbosa (bulbine lily). The terminal groups of flowers stand atop a fleshy green stalk up to 50 cm tall and are surrounded by an open skirt of tubular foliage.
All of these native lilies can be used to great effect in your garden, providing a seasonal display of bright colour and nectar for native insects such as butterflies and important predators like hoverflies. Mass –planted and grouped along garden borders is a great way to use these plants or scattered randomly through bush gardens to increase colour and diversity.
There are too many bulb forming lilies to mention here, and it is worth taking a closer look at local parks and roadside reserves to see what does well in your area. Surprisingly small populations of plants have survived urbanisation and are being conserved by local volunteers and councils to increase numbers. A great place in the southern suburbs to see them growing in the wild is the Black Road side of Minkarra Park at Flagstaff Hill or Beaumont Common in Burnside.