Gardening: Wise up on weeds

Chemical warfare should be a last resort for clearing out weeds. Other 'greener' methods are more effective. Photo / Meg Liptrot

You'll be surprised at how weeds can be used in your garden, says Meg Liptrot.

The extra rain this summer can be seen two ways. It is a blessing for gardeners, there is less need for irrigation, and therefore a cheaper water bill, or a curse because of all the extra weeding.

What constitutes a weed, of course, is in the eye of the beholder. A close friend of mine makes beautiful ink drawings of these often maligned and forgotten-about plants. It can also help to think of a weed as a plant in the wrong place, instead of turning to chemical warfare to deal with the "problem". Synthetic chemicals should be seen as a last resort for dealing with weeds, and it is certainly not an option in an organic garden.

Some weeds are useful indicators of the status of your soil. If your garden has plenty of creeping buttercup, it shows your soil is wet and has poor drainage. Some weeds are rich in certain nutrients. Black nightshade (inkweed), for instance, is full of potassium, and can be composted to increase potash for crops.

If you find you're growing a better crop of weeds than veges this year, don't despair, some weeds can be eaten. Dandelion and chickweed leaves can be added to a salad. Dandelion roots are commercially dried and baked then ground as a coffee substitute. Dogs love to snack on cleavers (biddibid) and it can also can be made into a healthy tea, as can nettle. If eating weeds isn't your thing, chooks will eat chickweed (it grows in the colder months) and they also do a good job clearing out tradescantia (its former common name was "wandering jew").

In home gardens, oxalis and couch (twitch grass) are some of the more annoying weedy perennials. Oxalis is abundant in summer, fortunately dying back as the temperatures cool, but the bulbs remain in the ground, waiting to emerge next summer. Couch grass has underground rhizomes which are relatively dormant in winter, becoming rampant in summer. It is native to temperate Europe, India and surrounding regions. Kikuyu grass is native to Africa. Both have excellent drought-proof qualities and make good turfgrass. They are tenacious when growing in the wrong spot, underneath prickly rose bushes, for example.

Rather than end up with backache and sore knees, the most time-efficient way to deal with these perennial weeds is to cover them. I don't recommend using woven plastic weedmat in border gardens, because the matting is there permanently, and a real nightmare to remove or dig through. Leaf material decomposes into compost on top of weed mat, becoming a perfect spot for windborne weed seeds to take root, defeating the mat's purpose.

I've found the best and cheapest option for weed suppression is to use plain brown unprinted cardboard, and it's a great way to re-use cardboard boxes. When you have collected enough boxes, open them up to a single layer and soak the cardboard for a few minutes in a wheelbarrow filled with water. Then place the cardboard around your garden plants, overlapping the edges. Apply shredded bark mulch 15-20cm thick (available in large quantities for a small price from arborists). Ensure you don't pile up the mulch against the base of woody trunks, as this can kill shrubs and trees. It is also best to use this technique after a heavy rainfall, or in the cooler seasons when the soil is moist.

Now you'll have plenty of time to enjoy your garden, instead of being a slave to the weeds.

Top weed tips

* Prevention is better than cure. Catch weeds before they seed. Always mulch bare soil as weeds need sunlight to germinate. Use spoilt hay as mulch to suppress kikuyu grass around young trees.

* Use a Dutch hoe to skim off weed seedlings on a hot, dry day. Simply disturb the surface to uproot them, the hot sun will do the rest.

* For paving where weeds are tricky to get out, use a Niwashi (Japanese garden tool) or carefully pour salted boiling water over stubborn weeds.

* Keep your lawn longer (adjust the blade on your lawnmower) as longer grass will smother daisies and other broadleaf lawn weeds.

* Got a weedy patch of bush at your place? Target one area at a time. Dig out Kahilli ginger roots and place in a barrel of water. Cover and allow to rot, then apply the resulting gloop back to the soil as fertiliser. For tradescantia, fill up a lightfast bag or container, then allow to rot, too. Add a compost activator to hasten process.

* For more information on dealing with weeds in native bush, contact the Weed Free Trust. Its War on Weeds campaign is on in west Auckland this month.