Gardening | You want healthy plants? Start thinking about nutrients

Nutrients play a key role in ensuring the health of your plants.
Nutrients play a key role in ensuring the health of your plants.

Healthy plants require a wide range of nutrients, in varying quantities. However, there are three main (primary) nutrients that are essential for good plant growth and productivity - Nitrogen, Phosphorous and Potassium.

The proportions of these elements in fertilisers are stated as percentages, using the respective symbols of N, P and K. Each element has a particular effect on plants, and fertilisers have varying proportions according to the primary purpose of the fertiliser. These include feeding, growth, flowering and fruit production.

However, a correct balance in these elements is also necessary.

Soil testing kits may be purchased, and nurseries offer testing of soil samples.

Nitrogen is a vitally important element, necessary for the green parts (chlorophyll) of leaves and good leaf growth. A deficiency in nitrogen will display as pale green to yellow leaves, with stunted growth. Leaf drop may also be present. If too much nitrogen is present, then leaves may be wilting and dead spots may appear on the leaves of young plants. There will be an excess of leaves that will probably feel soft and appear deep green in colour. Plants are often to attacks from pests and diseases.

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Organic means of adding nitrogen to soils include using composted manure, green manure and coffee grounds. Commercially produced fertilisers are also suitable.

Phosphorus is important for many areas of plant growth. As plants grow and cells divide, phosphorus promotes the growth of seedlings and roots, as well as the formation of flowers, fruits and seeds.

If plants are deficient in phosphorus then that may have a poorly developed root system, evidenced by slow growth, and leaves may have a purple tinge.

Excess phosphorus will lead to browning and dying at the tips of leaves, with the affected leaves falling from the plant. Yellowing of young leaves may be seen. Some Australia native plants, including those from the Proteacae family (banksias and grevilleas) may be affected by excess phosphorus.

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Superphosphate, added at appropriate levels, and animal-based manures are good sources of phosphorus.

Potassium is very important in plants to help them develop resistance to disease. It assists plants to produce chlorophyll, to make new cells stronger and to help water move through the plant's system. Potash is a source of potassium. Compost made primarily from food by-products is a good source of potassium, as well as banana skins.

If pots of Zygocactus plants were placed into areas where they only received natural light, once they had finished flowering last year, they should now be coming into full bud. Some earlier varieties may even have commenced flowering.

Zygocactus and certain other plants such as chrysanthemums and poinsettias set their flower buds when the hours of darkness reach a certain level.

Zygocactus are also known as Crab's claw cactus and Christmas cactus, as they flower at Christmas time in the Northern Hemisphere.

Pots of Zygocactus can be enjoyed indoors if they are placed in a well-lit position while they flower. Their pendulous stems and flowers make them most attractive subjects for hanging baskets, growing in a good draining potting mix. Plants perform best when the soil is kept evenly moist. Good air circulation in a position of filtered sunlight is ideal. Light feeding of a soluble fertiliser can be applied during spring and summer. Once the flowers buds begin to appear, the fertilising should be stopped, but it can be started again when the flowers have finished.

In order to enjoy the same display next year, it is important to again place the pots into an area of natural light.

CAULIFLOWER

Cauliflower is a very popular vegetable, particularly when added to cooked meals, although it is also most suitable for use as a raw vegetable in salads. However, it can be more difficult to grow as it can be frost sensitive as well as being intolerant of extreme heat. Cooler areas are the most suitable. A leaf should be broken and placed over the maturing head to prevent it from discolouring.

Plants form a white curd or flower in the centre of large cabbage-like leaves. Seeds should be sown in seed trays. They can then be transplantation out when they reach a suitable size. Plants will reach maturity in approximately 5 months from planting. Young plants should be spaced about 80cm apart. Cabbage white butterfly are the main pest of cauliflowers.

STRAWBERRIES

Strawberry plants can be planted out now, ready for the production of fruits in October and November.

Compost or aged poultry manure should be dug into the garden bed. Strawberry plants can be purchased in pots or punnets. These plants will be guaranteed to be free of virus diseases. Runners (long, thin shoots that are produced from parent plants) may also be used.

The new plants should be spaced about 30cm apart. An application of mulch will help in preventing weeds from growing near the plants. It will also keep the fruit clean.

As the plants grow they will eventually produce flowers. At this stage of the plant's growth an application of a liquid fertiliser, such as Nitrosol, should be made every few weeks.

Strawberry plants will continue to be at their most productive for about three years. After this time, new plants should replace the old plants, being planted out in autumn.

Strawberries can be grown in pots or hanging baskets, provided moisture and feeding is maintained.

GARDENING TIPS

  • As dahlias finish their flowering season and begin to die down, the stems should be cut off near to the ground, with the tubers then lifted and kept dry.
  • A new compost heap could be started now, using fallen autumn leaves as a base.
  • Select winter flowering fragrant shrubs, such as daphne and osmanthus, for an extra dimension in the garden landscape.

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