The hot weather, followed by humid, showery days is ideal for the formation of powdery mildew and black spot, on a wide variety of plants. Powdery mildew is easily recognised by the appearance of a covering similar to talcum powder over the leaves, stems and flower buds. Leaves covered with powdery mildew will become misshapen and eventually wilt and collapse. Flower buds will often fail to open properly. Vegetables affected by powdery mildew will give very low yields of fruit.
Powdery mildew affects large-leafed vegetables such as pumpkins, zucchini and cucumbers, as well as flowering plants, including roses, crepe myrtles and hydrangeas.
Newer varieties of crepe myrtles and hydrangeas have been bred to be resistant to powdery mildew so it is worthwhile to select these.
Because the mildew results from the weather conditions, it is sometimes difficult to control and often appears very quickly. An older style remedy that can be tried is spraying the plants with a mixture of five parts of full cream milk, diluted with one part of water. This will need to be reapplied every couple of days.
The butterfat from the milk stops the spores in the mildew from germinating.
Alternatively, fungicides that have been developed especially for the control of powdery mildew can be used. It is important to use follow-up sprays at the recommended strength and time intervals.
Some plants, such as crepe myrtles, have varieties that have been specially developed as powdery mildew resistant varieties.
The provision of a good air flow around plants will also assist in the control of powdery mildew.
Black Spot is a mildew disease appearing firstly as black spots on the leaves. The spots then turn yellow, giving the leaves an unsightly appearance. The leaves will eventually shrivel and then fall from the plant. The fallen leaves are still covered in the fungus spores, which can then spread to other healthy leaves. For this reason, diseased leaves should be removed from the ground under the plants and then disposed of in the garbage.
Certain varieties of roses have been bred to be 'black spot resistant / free'. A visit to local gardens or plant nurseries will indicate varieties that perform better in the weather conditions that are common in Australia at this time of the year.
Avoiding the watering of leaves on roses will help control black spot problems. Feeding the plants with sulphate of potash, at the rate of about 100 to 150 grams per bush about four times a year, will ensure stronger, healthier plants that will be more resistant to black spot. Spraying the plants will still be required A mixture of two teaspoons of bicarbonate of soda in 5 litres of water, with a couple of drops of detergent will make an effective and inexpensive spray. One of the commercially available copper based fungicides can also be applied.
Potted plants can make ideal Christmas gifts as the pleasure that is obtained from them will last for many weeks and may even be repeated in following seasons.
Foliage plants, such as ferns, ivies or succulents basically need just light and water in order to flourish. Brightly coloured leaves feature on plants such as crotons and coleus. These plants have multi-coloured leaves that often display a distinct pattern that is different from the others on the plant. A well-lighted position is necessary.
Poinsettias, with their deep / bright red bracts, have now almost become synonymous with Christmas decorations, due to the fact that they are available for purchase at this time of the year. The bracts will last on the plant for many months, provided that the plant has been placed into a position that receives a good supply of indirect sunlight. A wide variety of flowering plants is also available now. Mini roses grow successfully as potted specimens and they will provide flushes of blooms over quite a period of time. The colours of flowers are mostly in reds, pinks, yellows and whites. Many grow to approximately 30cm in height. Plants will be easy to prune as they will in general only require an all-over trim.
Potted annuals, such as petunias, marigolds, dwarf dahlias, gerberas, impatiens and phlox are ideal for people who have limited space, such as a small balcony, or those who are unable to care for more permanent plants but enjoy the beauty of flowers.
Other suggestions for indoor or balcony plants might include ferns, palms, begonias, philodendrons and begonias. A good supply of light is essential and plants such as ferns will benefit from being placed into an area with some increased levels of humidity, such as a bathroom.
Friends or relatives who enjoy cooking might appreciate a collection of potted herbs, or a Bay tree. These can be placed near the door so they are readily accessible when required for cooking, whether that be indoors, or outdoors such as a barbecue.
More experienced gardeners might enjoy receiving a more unusual variety of certain garden plants, such as one of the different varieties of hydrangea that are available. Some of these produce flowers that are quite different in shape, colour or form from the more common varieties. The "Endless Summer" range of hydrangeas, for example, flower on new growth and so have multiple flowering flushes throughout the growing season from late spring through to autumn.
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