With spring now with us I thought it opportune to discuss some issues that are most relevant to this period in the gardening calendar. Plants expend an enormous amount of energy in spring doing their things, like flowering and developing their fruit, or extending their size through new growth. Now is the time to help them along with some additional nutrients.
There are some fertilisers that can be applied to nearly all plants, like blood and bone, but these don’t have all the nutrients available that are specifically required by a particular group of plants.
Native plants are not fond of phosphorus for example whereas roses prefer a fertiliser high in potassium that helps them with lush and healthy blooms. Flowering annuals and vegetables prefer a higher rate of both nitrogen and potassium for both lush foliage and big and healthy flowers.
Plants that are grown in containers require care in the application of fertiliser as they can be severely affected by the incorrect application of certain fertiliser types. Powdered or granulated fertilisers should never be applied directly to the surface of the soil in the pots as most plants in pots are surface rooting and nutrient burn of these plants can be fatal. Use a slow-release pellet or liquid feed and again use fertilisers specific to the plant group. Keep in mind that nutrient depletion in pots is far quicker than for soil-grown plants so the process must be repeated more often to have the plants looking healthy all the time.
For those of us who prefer an organic garden there are many fertilisers now available that are BFA-certified organic.
All fertilisers should be well watered in, so the plant has immediate use of the nutrients. If you have mulch down around your plants rake it back, apply the fertiliser, water in then place the mulch back around the plant.
After the fertilising process has been completed the next important task is to apply either new mulch or to top up older mulch in preparation for the drier months ahead. I have mentioned in previous columns the types of mulches available and these range from shredded cow manure to sugar cane and lucerne mulch and other mulches from trees like pine bark and eucalypt chips.
The softer mulches like sugar cane and lucerne will decompose down over a shorter period than the wood mulches and, therefore, will require more frequent application. They are more beneficial to the soil as they improve the structure and texture of the soil as they break down. Wood mulches will tie up more of the nitrogen in the soil as they decompose than the softer mulches, so a keen eye needs to be kept on fertiliser application to ensure the plant is not depleted of this important nutrient.
For those of you in high-risk fire areas, a gravel mulch can be used and, although it hasn’t any nutrient value, it doesn’t burn or break down.
Finally, I need to mention the pests that start to invade the garden as the days start to warm and the sap is well and truly flowing. Sap-sucking or leaf-eating pests like thrip, aphid and caterpillars should be controlled as they can reduce the vigour of the plants which weakens the plants and allows other pests to invade.
There are two great control methods that are available to control these pests and are available now.
The first is a synthetic pyrethrum that is for use with the sap suckers and the other is a control that is derived from beneficial soil bacteria and is useful in the control of the chewing pests like caterpillars and other leaf eaters.
Call into your local nursery and check out all the new products that are available to make gardening more pleasurable and safer for our environment.