Monthly Archives: March 2014

Gardening Under Established Trees

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

Gardening Under Established Trees

Weevils and Associated Damage

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

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

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 high1 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.

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

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

The Native Grass Lawn – It is Possible

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

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

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.