Little and often is an effective strategy when it comes to keeping on top of garden weeds.
My garden is heavily covered in mulch. Of all my chores, mulching is the one I’m least likely to neglect, and although I couldn’t claim my garden is weed free, I haven’t had to spend the whole winter weeding. It’s that pleasant three-month 
reprieve nature gives us when our gardens creep along slowly, appearing to be under our control.
Already, though, I’ve noticed the weeds are on the comeback. Convolvulus is snaking through the hedge, sneaking out here and there as if I won’t notice. Wandering willy has shifted into the darker areas, and although I curse it, I know that yanking it out and leaving the pieces in full sun will see them turn to mush.
My rock walls are a protective host for oxalis, and I have no option but to ferret out its nasty little bulbs, which lurk like squirrelled hazelnuts, ready to burst into more.
At this stage, the situation appears to be under control, and it’s tempting to procrastinate a while longer, but I’m well aware that a day or two of thorough weeding now is going to save some back-breaking work later. It’s not just the rapidly increasing volume of weeds you need to think about at this time of year, it’s also the fact that the longer you leave them to become established, the worse your garden looks when you pull them out. Late-season weeds leave unpleasant gaps as well as unsightly defoliated areas on the sides of plants that have been shaded out by these opportunist competitors. The weeds are also stealing some of that money you’ve put into buying sheep pellets or liquid feed by soaking up the fertiliser as fast as you can spread it.
Although weeds may be unwanted, it’s worth taking the time to identify what you’re pulling out, as this can provide valuable information on control as well as an understanding of why it has weed status.
A handy and comprehensive guide is An Illustrated Guide to Common Weeds of New Zealand, by Ian Popay, Paul Champion and Trevor James. Reading through the botanically listed plants, you could at times feel as if you’re reading a plant-order catalogue: papaver, myosotis, olea, thymus, clematis, laurus, acaena … Usually it’s just one or two of each species that makes the list, but it indicates the source of most weed problems originated with us, the gardeners.
It’s not just the exotics that make the list; natives such as Leptospermum scoparium (manuka) and (the scented fern) are included. If you’re a farmer dependent on pasture, the country of origin doesn’t determine what makes a pest.
The illustrated guide is great because it specifies the area in which the plant is a problem. Thyme, for instance, can be readily grown in Auckland gardens without fear of a takeover, but in Central Otago and Canterbury it’s considered a weed that requires management. As climates shift and change, we need to remember there’s a possibility of innocuous plants becoming problematic. For these borderline plants, refer to your local council’s recommendations, as most councils keep lists of plants considered harmful or aggressive. This could be because of the damage they cause to areas of conservation value or, in some cases, because of a plant’s toxicity and track record in poisonings. Quite often these plants have bright-red or blue berries, such as many of the solanums, which are attractive to young children.
Many weeds are simply annoying, creeping from backyard to backyard, but when kept under control some can be useful as companion plants when grown near a vegetable patch. Borage and nasturtium are two examples.
For most plants that are pretty but troublesome, there is usually a closely related alternative that is less vigorous.
The importance of identifying weeds isn’t just about understanding the impact they may have on the surrounding environment or being aware of poisonous species that need to be kept away from children, pets or livestock. What you think is a weed may be a closely related treasure.
When we visited Hinewai Reserve on Banks Peninsula, a nature reserve managed by Hugh Wilson, we travelled through misty wet into icy wind. Sadly, we spent most of the time close to the hut, although there was the bonus of finding Hugh home and bombarding him with questions. There was plenty to learn. I noticed, for example, a white convolvulus floating over the trees and was surprised to see this pest in such a special place. Hugh pointed out it was a native species. Had this turned up in my garden, I would surely have removed it at once, despite its appeal.
Instead of using a book for weed identification purposes, try taking a weed sample to your local garden centre. Take a decent amount of the plant – ideally including a leaf and a flower – and make sure the sample is fresh. Having previously worked in garden centres, I can assure you a sample that’s been composting in the car for a week comes second only to no sample and a description of colour. A digital photo can also help with identification, especially one that shows the plant’s form.
In The Art of War Sun Tzu teaches us to know our enemy. Identifying weeds makes it far easier to know the best form of attack. Most weed advice offers information along these lines. Remember, the worst weeds are best kept out of the compost when they are in seed or if they divide readily and thrive in dark spaces, such as wandering willy.
That’s why it’s a great idea to get stuck into the weeding now before anything goes to seed. Now all I need is the time.