Choose trees for autumn colour

If you want to plant trees with stunning autumn colour, have a good look around your neighbourhood before it’s too late.

Catalogues are great, but they usually show a species at its very best, under optimal conditions, and it is important to remember that not all trees deliver a full autumn fanfare in all regions.

Some of the best autumn foliage is delivered by the maple (Acer) clan (pictured). It’s worth finding one to suit your locale and situation because there are many sizes – from giant to dwarf – within this genus. Sugar maples (Acer saccharum) grow well in Auckland but may fail to deliver much in the way of autumn colour.

My Japanese maple (an unnamed Acer japonicum variety) coloured beautifully in many shades of plum purple last year but this time around the leaves are turning brown and crisp before showing autumn colour.

DIY FROST PROTECTION

The climatic differences between gardens in the north and the south can be hugebut frost affects nearly every region, and a light frost in Northland can cause significantly more harm than a heavy frost in Southland (ff you’ve had your first frost already, let us know and send photos to inbox@getgrowing.co.nz).

Frosts are most likely on nights when the weather is clear, dry, still and bitterly cold. Protect seedlings until they establish themselves. This can be as simple as pegging a few sheets of newspaper as a cover, or buying a roll of frost cloth to keep on-hand for when frost threatens.

Drape old net curtains, bubble wrap, clear plastic or horticultural mesh over wire hoops to form a tunnel for protecting plants in winter.

Curtains and mesh allow water to pass through but remember to water plants under plastic.

Rescue old plastic bottles from your recycling and cut the bottoms off to make mini cloches for seedlings. Make holes around the bottom with a hole punch so you can secure the bottles in place with wire staples.

And frost isn’t all bad. A good frost actually sweetens the taste of swedes, broccoli, cabbage, kohlrabi, parsnips, kale, swedes and brussels sprouts. This is actually a survival mechanism. When frosts hit, these plants start converting the starch in their cells to sugar (a natural antifreeze) to reduce the water content.

TAKE CUTTINGS FROM FROST TENDER PLANTS

Frost blackens perennials such as coleus and pelargoniums. As insurance, take cuttings now so you have lots of sturdy plants to transplant in spring. Autumn is also a good time to take cuttings of rosemary, lavender, fuchsias, hydrangeas and other shrubs and hedging plants.

When taking cuttings, choose a sturdy stem and cut just above a node (where leaves or buds are attached). Nip off any flower buds and remove the lower leaves. Dip the cut end in rooting hormone powder or gel if you have some handy, although it is not essential.

Insert cuttings around the edges of containers of potting soil mixed with pumice or perlite for good drainage.

Place in a well-lit but sheltered, frostfree spot and keep moist. When roots show at the drainage holes, repot into individual pots.

LET DAHLIAS DIE BACK NATURALLY

Autumn is a critical time for boosting tubers so they flower well next year. dahlias should still be in leaf in nearly all parts of New Zealand, although

GET GROWING

This column is adapted from the weekly e-zine, get growing, from New Zealand Gardener magazine. For gardening advice delivered to your inbox every Friday, sign up for Get Growing at: getgrowing.co.nz flowering will be coming to an end now. Do not cut dahlias back, let them die back naturally.

Paul Hoek from NZ Bulbs recommends treating powdery mildew (a white coating on the leaves) if present. Not because the tubers will get infected but because now is the time that the dahlia plants put energy into tuber production rather than flowering. If left untreated the mildew will reduce the ability of the leaves to make energy to feed the developing tubers.

Powdery mildew is easily controlled using either a combined insecticide and fungicide spray or a more natural fungus spray containing copper and sulphur.

You can also spray with baking soda using half a teaspoon to a litre of water.

Add half a teaspoon of washing-up detergent to help it stick to the leaves.