In the Garden this Fortnight: January 26, 2012

A fortnightly series first published in the Weekend Gardener and reproduced here with their permission.

The dreaded Onehunga weed needs active management

The dreaded Onehunga weed needs active management

Onehunga weed is that innocent looking but prickly interloper to the lawn which makes walking in bare feet a misery. It is an annual weed and the prickles are part of its seed setting cycle. We had an invasion of it in some areas and rather than spraying, we tried scalping the lawn just before Christmas. By scalping, I mean cutting on a very low level and removing all the clippings to the compost heap. We normally mulch the clippings back in to the lawn. The lawn looked patchy for the next few weeks but the Onehunga weed was gone – including the new crop of seed heads. There is a risk element to this approach. Had we then struck a prolonged period of high temperatures and sun, we would have had to have started watering the lawn or watched a dust bowl develop. Scalping a lawn in early to mid summer is not usually recommended. As it happened, we had plenty of torrential rain to green up the lawn again.

You can spray for Onehunga weed (though you need to do it earlier in the season before the plants flower and set prickles) but we are increasingly reluctant to use lawn sprays, leaning to the view that maintaining one’s lawn chemically is getting close to environmental vandalism. Recent research from Massey has found a new strain of Onehunga weed which is resistant to the usual lawn sprays -another warning, perhaps, about gardening strategies that depend on chemical intervention. The weed generally germinates in autumn and grows through winter to flower and die in summer. If you have a lush, healthy lawn, it will find it harder to get going in competition with established grasses. Lifting the mower a notch or two higher can help keep a lawn in better condition (a scalped or shaved lawn is never a healthy lawn) and we are big advocates of using a mulcher mower, thereby avoiding having to feed the lawn. Where we need to over sow or renovate areas, we use homemade compost rather than proprietary fertiliser. Our lawns don’t look like bowling greens but they are generally healthy and green.

Onehunga weed is shallow rooted so if you only have a small area of grass, you can hand weed it. It is always better to get in early before it spreads – which it will do at alarming speed if you ignore it.

This one is auratum Flossie - all the lilies are opening now
This one is auratum Flossie – all the lilies are opening now

Top tasks:
1) An emergency staking round on some of the top heavy auratum lilies. We grow a lot of these for summer fragrance and blooms. Because they are garden plants and not show blooms, we support the flower heads on neighbouring plants where possible, but some just have to be staked. Home harvested, fresh green bamboo stakes are less visually intrusive than bought bamboos stakes. We shun plastic stakes but will use rusty old steel on occasion.

2) The rose garden is looking tired. I have major plans for a renovation of this area in winter but will start by lifting and dividing some of the stronger perennials, potting them to planter bags and keeping them out of sight and under irrigation while they recover. It takes many more plants than anyone ever expects to furnish a garden which has been gutted out. I need to start now to have sufficient plants to do a major rework and replant in winter.