Summer boom-time is over, but this is not a go-ahead to retire to the couch. Autumn can be busy and productive in the garden, and it's a nice time to be out in the crisp air. In autumn, deciduous trees stop producing green chlorophyll in their leaves as they face the cold winter. The trees conserve their resources, and the leaves turn yellow and drop off. Evergreen leaves tend to be more leathery and will resist damage from the cold, so remain on the tree. Most New Zealand native trees are evergreen.
Autumn leaf litter is a way for nutrition to return to the soil. Macro and micro invertebrates such as earthworms, slaters, mycorrhiza (beneficial soil fungi) and bacteria help to break down old and decaying plant material, and return it to the soil, adding carbon via organic matter and building topsoil, while increasing soil nutrients.
This is often the best time to prepare the ground for planting trees and shrubs, whether they're ornamentals or edibles. If it's rained recently the ground should be soft enough to dig. If your soil is still rock-hard leave it until you've had another good rain and see if that makes a difference. If not, winter may be your best bet for planting and garden development.
For those who already have damp soil, planting now is better. Leave it until winter or early spring and your soil will likely be heavy and gluggy and you will damage its structure digging in such conditions. As mentioned a couple of weeks ago in my story on green crops, using hay is an excellent way to help prepare soil for planting, particularly if you are planning deciduous fruit trees, which often aren't available to purchase until winter. A quarter bale of spent hay, placed where you plan to plant your tree, will, in a couple of months, have rotted well underneath. The rotting hay and topsoil will be full of worms and the soil loosened, perfect for planting in. Just prise the bale apart and plant into the soil below.
In the ornamental garden, autumn is an important time to clean up. Remove spent or dead stems from flowering perennials such as salvia.
Passionvine hoppers seem to favour members of the salvia family to lay their eggs on, so removing the old stems will reduce the numbers of the pest next summer.
Evergreen hedges can have a final trim before winter. Avoid trimming spring flowering shrubs. I've left the new growth on our manuka hedge to ensure we get a great display of flowers in spring. Hibiscus can be lightly pruned back after flowering. Pruning too hard before winter may encourage new growth, which will be frost sensitive. New hibiscus foliage tends to go yellowish in winter, giving the illusion it is suffering from nutrient deficiency in response to the cold. But once it grows again in summer they come back to their old selves with lush, dark green foliage.
Spreading a little slow release organic nutrition around perennials, trees and shrubs, such as sheep pellets, rock dust and a little dolomite will ensure that, come spring, the plants will have the nutrients they need. The soil temperatures are warmer now than they are in spring, so soil organisms will still be active to break down organic material and rock minerals into plant-available nutrition.
Using natural rhythms takes time in the garden. It is certainly a better, more sustainable approach than pouring quick-fix fertilisers on your plants in spring and summer.
* Stop dead-heading roses so rose hips form. They contribute autumn colour to the garden.
* Trim hedges, sow new lawns, or resow patchy lawn after lightly tilling soil.
* Plant bulbs, sow spring flowering annuals like sweet pea, aquilegia, poppy, calendula, ornamental lupin.
* Cut back spent summer perennials, divide clumping species, replant. Take woody
* Wait until leaves have all dropped off deciduous shrubs and trees before pruning - mid-winter is best.
* Now is a good time to make compost; add garden clean-up materials. Pull out dry, dead annuals, and layer in the compost. These will ensure compost isn't too wet and gluggy.