How to deal with invasive weeds

Invasive weeds can destroy the most carefully planned and executed garden – and blight the whole neighbourhood! In this article, horticulture expert Jon Muller reveals his top tips for dealing with them – and some ideas landscapers can use to turn a one-off job into an always-on stream of work

I have a slightly obsessive thing about weeds. Whenever I visit friends, I check the gardens

and note any weeds they might have. For example, when staying in Northland recently, I couldn’t help but note the infestation of woolly nightshade and wild ginger, so I got to work trying to contain its spread before it flowered.

Weeds are a particular problem in Auckland and Northland. Did you know that Auckland is the

weediest city in the world – and Waiheke Island is the second most weedy island!? That’s not a great endorsement for the green spaces in the region, so I like to do my bit whenever I’m there.

You don’t often read about weeds or soils in gardening books, but I made a point to include both in my Wellington Gardens book, as so many of my clients have issues with weeds.

Get on top of them before they get on top of you

There is a saying: ‘one year’s seeding, seven years weeding’. Once you let the weeds seed, you have let the horse bolt, as it were. I recently contacted our local council regarding one of their new gardens that needed weeding – but, when the job was finally done, the weeds were all beginning to re-emerge, as the seeds were established in the soil. Perhaps the correct motto should be ‘weeding in time saves nine’!

If you are planting a garden for a client, in the initial stages it is imperative that you allow the good plants to grow at the same time as controlling the weeds. Weeds compete with plants for light, moisture and nutrients, and can harbour pests and diseases.

Weeds are also opportunists, so, if you leave any bare soil, nature will find a way of growing a plant in it. Most likely the weed will be hardier than your ornamental plant, so you need to favour your desirable plants until they cover the soil and not let weeds get a foothold.

Always have a plan... a maintenance plan

If I install a garden, I make sure to organise the maintenance or ensure the client has the skills, knowledge and time to prevent weeds from flourishing. One way to do this is by handing out maintenance notes once the garden is complete. Another way you could make sure clients prevent weeds from establishing themselves (and possibly secure yourself additional work) is by offering free WOF checks on their gardens. It’s especially important to seize the opportunity for downstream work, such as maintenance, during quieter economic periods.

I recently offered the WOF check for several clients and was employed for monthly maintenance by those having weed issues as a result. A few months down the line, the gardens are looking great and relatively weed-free. There is nothing worse than seeing a garden you installed with weeds knee high. It’s not a good advertisement for you or your

services either!

As landscapers, the proof of the pudding is in the seeing. That means the gardens or structures we leave behind can do your marketing for you. Potential clients can see them every day, and you should want the work you do to be presented in the best way possible! For gardens, that means helping your clients to keep them weed-free and looking great.

If you are thinking of entering a garden in the Landscapes of Distinction awards, then make sure it is well maintained. Apart from weeding, this includes fertilising, watering, pruning and pest control. As part of my job, I explain to clients that weeds can be found in the original soil, but many are airborne – so just putting down a weed mat doesn’t ensure your garden will be weed-free.

Old man's beard is not a one-person problem

It’s important to factor the environment into your weed-free plans. For example, even if your client’s garden – and most others in the neighbourhood – are weed-free, if one garden on the street isn’t, the weeds can migrate.

This is especially the case with noxious weeds like old man’s beard (Clematis vitalba), blackberry (Rubus fruticosus) or bindweed (Convolvulus). It then becomes a constant battle to keep your property weed-free. We have neighbourhood groups who work on controlling old man’s beard in Wellington, but it’s annoying if one property infests all the others.

One group, Old Man’s Beard Free Wellington, is voluntarily working on eradicating this problem. Check their website www.ombfree.nz for more information.

Kaitiaki o te Ngahere (Guardians of the Forest) is another organisation that manages natural spaces, including weed control around Wellington.

You should have similar groups in your local area. As professionals, we can work in tandem with councils and neighbourhood groups, as well as our clients, to combat our weed problems! Hopefully Auckland can cease to be the weediest city in the world as well!

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Jon Muller has owned Wellington Gardens Ltd for 24 years. He practices landscape design and

construction, with an emphasis on planting design. He has taught at polytechnics and university, mostly in soft landscape subjects. He has written six gardening books, including Wellington Gardens, and enjoys helping clients find landscape solutions. He also helps students and workers studying for their landscape qualifications.