Growing Yaccas in the Home Garden

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.

Xanthorrhoea quadrangulata

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.

Xanthorrhoea quadrangulata

Nectar of the Gods; Nectar Plants for Native Wildlife

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By Mark Thomas

Attracting native wildlife to your garden is rewarding and fun as well as educational. As I type this article, eastern spinebills and New Holland honeyeaters are battling it out for air supremacy, feeding from various nectar plants in our garden and cautiously flying from shrub to shrub. A large variety of native plants are available producing suitable nectar for wildlife without the risk of spreading diseases that can be prevalent when using feeders.

The Proteaceae family (Grevillea, Banksia, Hakea, Adenanthos etc.) have many fantastic nectar producing species and cultivars that wildlife will relish:

Grevillea “Ned Kelly” and G. “Robyn Gordon” have beautiful big, pink flowers year round. A wide range of nectar feeding birds and mammals such as ringtail and brush tail possums will delight in the flowers and new growth tips. The plant needs good drainage and direct light but may suffer from chlorosis (yellowing of the foliage) in soil exceeding pH8.5.

Grevillea ‘Robyn Gordon’

Banksia marginata and B. praemorsa have large yellow flowers as well as a wine red form of B. praemorsa also being available. Eastern spinebills, New Holland honeyeaters, wattlebirds and other species of honeyeaters feed directly from the flowers while clinging on to them. Possums, pygmy possums and feathertail gliders will enjoy the nectar. These particular Banksias will grow in most soil types if given good drainage and plenty of sun.

Callistemon or bottlebrush is a genus that produces great nectar from copious flowers, attracting a large range of nectar feeding birds and mammals. Callistemon citrinus “Splendens” is a large shrub with lime green foliage, bronze- red new tips and bright red flowers for most of the year. It will grow in all soil types including waterlogged areas.

Calothamnus, netbush or one sided bottlebrush is a smaller genus of plants with the most commonly grown species being Calothamnus quadrifidus. They have fine needle-like foliage and bright red or yellow flowers through spring, summer and autumn. The plant is tolerant of most soil types if given full sun and attractive to all the wildlife mentioned previously.

Correas such as Correa pulchella are South Australian endemics (grow naturally only here). They have a wide range of forms from ground-cover to shrub and are attractive to nectar feeding birds, particularly the eastern spinebills which regularly seek them out when in flower. Flowering on various forms is from late summer through spring. Plants will do best in part shade or protection from afternoon sun and tolerate most well drained soils.

Correa pulchella ‘Big Red’

Native Bulbs for Winter Colour

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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.

Calostemma Purpurea

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.

Bulbine Bulbosa

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.

Mycorrhizal Fungi as Beneficial Organisms to Plants

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By Mark Thomas

Fungi, although not plants themselves are often closely linked to the survival of plants through the formation of symbiotic relationships, these are called Mycorrhizal Fungi. Up to 90% of plant species rely on such symbiotic relationships with fungi for the increased uptake of essential nutrients, increased disease resistance and drought tolerance. It has been estimated that up to 15% of the biomass of all plant roots are actually fungi¹. Some individual fungal colonies can be massive with sizes of up to 15 hectares and weighing 100 tons¹.

Fungi do not contain chlorophyll; the photosynthesising pigment found in plants and so must rely on the nutrients obtained from the breakdown of organic material. Mycorrhizal Fungi, like many other types of fungi have filamentous hyphae that form a web- like network called mycelium which release enzymes into the organic matter substrate and re-absorb the released nutrients. The difference is that in the case of the mycorrhiza these nutrients are transferred to the plant via a beneficial infection directly to the roots of the plant either outside of the root (ectomycorrhizae) or through the cell wall of the outer roots (arbuscular mycorrhizae).

Mycorrhizal Fungi Photo: Mark Thomas

The fungi in mycorrhizal associations act as extensions to greatly increase the surface area of the plants root- system and increase soil contact. Nutrients such as phosphorous, zinc, copper and several forms of nitrogenous compounds are transferred from the fungi to the beneficially infected plant in exchange for sugars produced by the plant via photosynthesis². Many authorities suggest that the increased surface area also extends the ability of the plant to uptake more moisture in the soil, increasing drought tolerance⁴. Dominance of the rhizosphere or root- zone of the soil by beneficial fungi interacting with the plant can act as a powerful defence mechanism.

Harmful fungi can be kept from infecting the roots of the plant if a beneficial infection already exists³. More than one species of fungi can infect the roots of a plant with many fungi infecting and in so doing connecting large numbers of plants in one area¹.

The difference in soil texture may also be important for mycorrhizal fungi as lighter or more open soils are easier for the hyphae to penetrate and extend the root zone. There would be a definite benefit for heavier more compacted soils if organic matter such as compost was incorporated into the soil to encourage the rapid expansion of the plant- fungi association. The beneficial infection is very important in phosphorous depleted soils such as those throughout much of Australia as small amounts of the nutrient can be quickly cycled back to plants from dead organic matter. Some plants don’t have such a relationship with fungi, for example some native families; Proteaceae, Chenopodiaceae, Cyperaceae, Juncaceae. These plants have alternative methods for dealing with the cycling of small amounts of vital nutrients such as the Banksias, which have proteoid roots that have a very large combined surface area. They can uptake nutrients directly for the plant in a similar way to the fungi through exploiting organic matter that is not yet decomposed.

1– Raven,P, Johnson,G., Losos, J.& Singer, S. 2005, Biology,7th Ed,Mc Graw- Hill,U.S.A
2– Fuhrer, B 2005, A Field Guide to Australian Fungi, Bloomings Books, Melbourne
3– Marschner,P.2004, Soil Ecology & Nutrient Cycling lecture notes, University of Adelaide
4– Buchanan, R.,1989 Bush Regeneration, Recovering Australian Landscapes, Tafe N.S.W.

Gardening Under Established Trees

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By Mark Thomas

Gardening under trees can be difficult due to factors such as shade, root competition, reduced moisture, reduced nutrients and in the case of some trees allelopathy. Allelopathy is an ability some trees such as Eucalypts possess whereby chemicals secreted from the root system blocks growth and germination of other plants.

It is tempting to give up or plant the whole garden to Agapanthus as many gardeners in the Eucalyptus dominated areas of the hills currently do. An alternative is to use plants that naturally grow under trees that can cope with all the limitations while still looking great and attracting wildlife to your garden.

One of the most versatile groups of plants for this situation is the Correas, with many colours, sizes and forms available thriving in dappled light and semi- shade as well as coastal conditions. Where height is needed for screening or structure Correa alba var.alba is reliable in any well drained soil including clay that has had gypsum treatment. The bell shaped flowers are a magnet for nectar feeding birds and the dark green leaves have a contrasting light undersides.

Lower and with lots of bright colour are Correa “Jezabell” and Correa “Catie Bec” for highlighting garden edges and rockeries with pink bell flowers. There are even a few groundcover forms such as Correa pulchella “Autumn Blaze” with bright orange flowers found originally growing on Kangaroo Island.

Goodenia thrive in understorey conditions, most with masses of bright yellow flowers and fantastic for cottage style gardens as well. With many different species and forms available there are choices of large shrubs down to groundcovers. One species that would have grown on the Adelaide plains but still grows in some areas of the hills and coastal areas is Goodenia amplexans. With large leaves and fast growth this plant is very attractive, great cover for rockeries and likes being pruned which keeps the plant growing tightly.

Doryanthes are large lilies from Eastern Australia with leaves of mature specimens reaching 2-3m and masses of flowers on tall stalks. Both species are best suited to large spaces and are happy growing at the base of tree trunks. These plants are bold statements with strong architectural form.

Lomandra are generally smaller members of the lily family and most species are right at home with dappled light. They are ideal for edging and borders or just creating foliage contrast, especially if you have used a lot of shrubs in your design. Lomandra confertifolia “Little Pal” has a soothing and graceful lime green foliage that is soft to the touch. Lomandra multiflora ssp. dura is a local species little known or used in horticulture but with great potential. It has stiff silver –blue foliage with contrasting yellow flowers and the ability to cope with long periods of drought when established. Butterflies love the flowers and the foliage is host to the rare Phigalia Skipper butterfly while the seed is food for skinks.

Using plants that suit your conditions will always produce better results than trying to change your garden to grow plants that are incompatible. There are usually a large number of native plants that could suit any garden situation while saving water, providing food for wildlife and unique beauty.

Gardening Under Established Trees

Weevils and Associated Damage

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By Mark Thomas

During prolonged dry weather some plants may begin to exhibit mysterious damage to leaves, shoots and stems. The damage can seem to appear without any apparent culprit and become increasingly more intense each day the plant is inspected. What can be most frustrating is that much of the damage appears on the fresh new growth, disfiguring foliage with irregular holes or grazing of the upper green tissue of leaves and stems. Sometimes leaf blades or stems are left hanging limp after being partially chewed through. If you have plant damage that fits this description weevils are one very likely culprit, although crickets, grasshoppers and katydids can also produce similar damage.

Weevil feeding on a Correa

Weevils are stealthy plant predators that come out of the mulch at night to feed by crawling along the stems and chewing the surface of the leaf leaving white patches that dry up and become paper- like in appearance. A couple of individuals may be responsible for all of the damage to one plant with the accumulated effect being substantial. Their small size and camouflage colouring make them difficult to see, along with their nocturnal preferences. They have a distinctive elongated proboscis which makes telling them apart from other beetles easy. When frightened or touched they will pull their legs in and drop to the ground where they are nearly impossible to find and will resume feeding when danger has passed. Correa species are particularly attractive to attack although anything with soft or slightly fleshy foliage can be attacked such as Myoporum, Stylidium, Acacia and many others.

Detail of a weevil showing the distinctive long proboscis

Control is probably best by hand removal at night with a flashlight and something to hold beneath the shrub to catch any that fall. Most literature also recommend Carbaryl, Maldison or Pyrethrum if numbers of weevils become too high^{1 2} although only in extreme situations as these chemicals can effect natural predators as well. Application of chemicals is also made more difficult due to the nomadic nature of the weevils. Such chemicals should only be used strictly as per the instructions on the container as toxicity to humans is possible also. Natural predators to weevils include lizards, frogs, birds, rodents, some marsupials, wasps, fungi and bacteria. The response time from natural predators may not be as quick as many people would like but if allowed to do their job natural predators and hand removal should usually take care of the problem and keep the natural balance in your garden.

¹Jones,D. & Elliot R. 1986, “Pests, Disease & Ailments of Australian Plants” Lothian Books, Melbourne

²McMaugh, J.1985,” What Garden Pest Or Disease Is That: Every garden problem solved, Landsdowne Press, Sydney

The Native Grass Lawn – It is Possible

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By Mark Thomas

With lawns well established in the urban landscape and water scarcity an issue, people are looking for alternatives to traditional lawns and the maintenance needed for their upkeep. One possibility is to convert lawn areas to garden beds utilizing low water use Australian native plants. Alternatively an Australian native grass patch could be established for areas that require pedestrian access such as children’s play areas, under clotheslines or just for a patch of soothing green. Australian native grasses have a different character, usually forming natural tussocks or spreading rhizomes in a wide array of shapes, colors and textures.

For semi-shaded areas or where there is dappled light Weeping Rice Grass (Microlaena stipoides) would be a useful, low, rhizome spreading species that will take mowing. This species will require a couple of summer soakings to stay green. In similar areas Dichondra repens could be used. This species has round leaves to approximately thumbnail size with a very low habit growing along creeping stems that root at the nodes. It can be used exclusively or mixed with other shade tolerant species to fill in areas under trees. Dichondra will require regular watering to remain green through the hottest part of summer although if allowed to brown off it will return with moisture.

Dichondra repens

Kneed Wallaby Grass (Danthonia geniculata) could be used in open areas with cool climates and mowed. Care would need to be taken to allow the seed heads to remain until after autumn to reseed the grass-patch. In areas that receive more direct sun species such as Red-leg Grass (Bothriochloa macra) can be used. This grass has a low, spreading, tussock habit with red tinted stems and leaves.

Microlaena stipoides

At Gondwana Landscapes and Consultancy we recommend treating the area to be sown or planted with grass tube stock as a revegetation area and getting firm control of weeds first. A weed-free patch will require less mowing to remain looking good, giving you more time to enjoy your garden.

Butterflies in Small Gardens

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By Mark Thomas

Common brown (male)butterfly feeding on nectar of Senecio odoratus

Attracting butterflies to your garden, particularly native Australian species can be very rewarding and take little effort. With a little planning and an understanding of the butterflies needs you can attract butterflies to live and reproduce in your garden instead of being an occasional visitor. It is important to stress here that the larval stage of butterflies or caterpillar will feed on plants in your garden leaving chewed leaves and “damage’ to plants. Some grazing will have to be tolerated if butterflies are to proliferate in your garden.

Incorporate some locally indigenous plant species in your garden as sources of nectar and host plants or food for the caterpillars, these may be on separate plant species and can sometimes be very specific. A diversity of plants with different flowering times throughout spring to autumn are the best way to attract a wide range of butterflies.

Grass areas that are a little neglected and un-mowed can be beneficial to some butterflies, especially native species such as: Microlaena stipoides var. stipoides, Themeda triandra, Austrodanthonia species and Poa species. Grasses can be valuable food and habitat for the caterpillars that will eat the leaves.

Some open areas for the butterflies to warm up in sun with rocks or paving to allow them to absorb the heat from surfaces. When designing gardens for butterflies, large unprotected areas of paving should be avoided.

Some shade or dappled light, this can be supplied by nectar plants that will also produce shelter.

A source of water, particularly ponds, dams, water- bowls or frog ponds allow the butterflies to drink or cool down when temperatures exceed 35^oc. Sedges can be incorporated into wet areas as many native species perform the role of host plants and look great.

Consider adding extra layers of vegetation to gardens that lack understorey. Gardens with only trees and shrubs would benefit from groundcovers and grasses as well as appear more natural.

Below are two short lists of plants to try in your garden, however there are many others to add.

Shrubs/ groundcovers for butterflies (nectar):

Acacia species –most
Atriplex species- most
Bursaria spinosa
Cullen australasicum
Goodenia species-most
Hardenbergia violacea
Indigofera australis
Myoporum species -most
Swainsona formosa
Templetonia retusa

Shrubs/ groundcovers to host caterpillars:

Adriana quadripartita
Chrysocephalum apiculatum
Eutaxia microphylla
Kennedia prostrata
Rhagodia candolleana ssp.candolleana
Scaevola species- most
Senna artemisiodes ssp. coriacea

Resources:

“Attracting Butterflies to Your Garden, What to grow and Conserve in the Adelaide Region” Hunt, L , Grund, R, Keane, D & Forrest,J 2007.