May Hints

Ash Whitefly is becoming a significant pest of ornamental trees and shrubs, mostly by the copious amounts of honeydew secreted by juveniles and deposited on cars parked under a tree. As Ash trees lose their leaves, the whitefly will move to other plants to over-winter. There are over 60 ornamental plants identified as hosts to Ash Whitefly. Among the more susceptible are citrus, photinea, apple and pear and pomegranite. Spraying with insecticides may help to control this relatively new pest, but the best control is garden hygiene. Rake and place fallen Ash leaves in plastic garbage bags and leave them in the sun to “solarise.” If temperatures are warm enough this will kill many of the eggs. If the leaves are left on the ground or put on the compost pile the whitefly eggs will survive until next spring to invade your garden all over again.

Remove deciduous leaves that have fallen onto lawns. They block sunlight from the grass at a time when the number of daylight hours are reducing, preventing the turf chlorophyll factory from producing sugars via photosynthesis.

Soursobs have commenced to grow and are quite susceptible to herbicide sprays now.  Best results will be obtained by using metsulfuron, but as this is difficult to obtain in small quantities for the home gardener, and the amount of chemical needed to cover 100 square metres is a minute (0.05 of a gram!), we recommend asking your local ALMA contractor to apply this for you.  The bonus is that metsulfuron will also eradicate other broadleaf weeds that are present in your lawn.


Deadnettle and chickweed are two winter annual weeds that continue to thrive in lawns. Deadnettle is an upright plant that produces a characteristic small purple flower. Chickweed is a low growing weed that forms a dense mat. The leaves are bright green with somewhat woolly leaves and a white flower. These weeds are quite obvious this time of year in thin areas of the lawn.


Bridal creeper is proclaimed for active control throughout the State. Sale and transport of the plant is prohibited. Advice on recognition and control of noxious weeds can be obtained from local Councils, the State Herbarium Home Garden Advisory Service or the South Australian Animal and Plant Control Commission. Bridal creeper, Asparagus asparagoides, is a native of southern Africa and is a major environmental weed in southern Australia. In dense infestations the underground tubers, representing up to 90% of the weed’s biomass, form ‘mats’ under the soil surface that prevent native seedling establishment.

Commence pruning hydrangeas as the leaves yellow and drop and new buds start to form. Prune older stems back to half their original length, cutting to a new bud. Thin congested stems to open up the shrub and encourage healthy new growth.

Pink hydrangeas will produce blue flowers if the soil pH is below 5.5. Apply a pH lowering agent (agricultural sulphur, alum, sulfate of iron, Lawn B etc) every four weeks from pruning time until flowering has finished at the end of summer.