A weed can be any plant growing where you don’t want it to, but there are some particularly weedy species to keep an eye out for. Weeds come in all sizes, shapes and growth forms, and are found everywhere, not just in your garden. Different types of weeds have different impacts.
Dealing with weeds is an important part of caring for your garden. If left unchecked, they can quickly overwhelm, disfigure, or kill your wanted plants and lawns.
Here in New Zealand, we have some of the best growing conditions for weeds. While it would be nice to call that an achievement, it means we’re fighting a losing battle against common lawn weeds.
There are several weed species that thrive in NZ lawns, many look very similar to each other, yet vary considerably in their susceptibility to chemical control. Most weeds integrate well with other plants in a new ecosystem, but some species become invasive, crowding out native plants. New Zealand has it all. Clearly the correct identification is vital before any treatment is applied.
To help you identify weeds on your lawn, here are the five most common ones we encounter on a regular basis.
Some of the most common lawn weeds in New Zealand
Clover is a perennial weed that is low growing and found in most lawns. Farmers in NZ go to a lot of trouble to get clovers growing in their pastures; Green keepers go to as much trouble to remove them from turf. Some D.I.Y gardeners like white clover in their lawn but Green keepers generally try and remove it for a number of reasons including the patchy appearance they give turf and the prominent flowers they produce. If turf can be kept dense and competitive during autumn when the annual clovers are germinating, establishment of the seedlings is less likely to be successful.
If you’re a farmer, you’ll love clover. But if you’re a homeowner, you’ll be trying to get rid of it. Clover can take over quickly and is one of the most common lawn weeds in the country. It’s also a legume, which is why farmers love feeding it to their livestock. When it takes over your lawn, it’s slippery to walk on and attracts bees.
Clover has three leaves and white flowers. Sometimes, it has four leaves.
How do I control it?
On a farm, you can let livestock feed on it. To combat clover head on – Dig out clover by hand (ensure all roots are pulled out) or apply a selective herbicide to the lawn, this will kill the clover without harming the surrounding grass. Depending on the degree of infiltration a repeat application may be required.
2. Onehunga Weed
It normally acts as a winter annual. This means it spends most of summer as a dormant seed in the soil. It germinates in autumn once the soil becomes moist but before the lawn recovers from summer dryness. If the lawn cover hasn’t died back over summer, Onehunga weed seedlings have much more trouble establishing. Once they are established, the plants grow throughout winter then produce clusters of spined fruits near ground level ready for some unsuspecting passer-by to step on them and distribute the fruits elsewhere in the lawn in their feet or jandals. Once the lawn begins to dry in summer, the plant dies, having completed its life cycle, though the spiny fruits are often left with spines sticking upwards even though the plant has died. It doesn’t always grow as a winter annual though, as it can also establish in spring under some circumstances.
When it’s dying, it’s hard, spiky, and ready to cause damage to skin. Named after the locality in Auckland where this weed was first seen, Onehunga weed is an annual weed with a very small root system. The seeds are very distinctive with their sharp spines (prickles) which readily attach to bare feet. in summer. Onehunga weed is generally found throughout the North Island. It often invades in autumn in turf which has bare patches following hot dry summer. It produces seeds and dies the following spring – summer.
How do I control it?
You can spray Onehunga. Onehunga weed can be sprayed but you need to get the timing just right for an effective outcome. Whatever herbicide is used on the Onehunga weed, obviously it is best to kill the weed before the fruits begin forming, otherwise prickles will still end up in the feet of people walking across the dead plants. Talk to your local gardening expert about what to use and when to do it.
Its botanical name is poa annua but you might also know it as winter grass, annual bluegrass, annual meadow grass or simply poa. It is possibly the most common and troublesome weed and people don’t like because it is temperamental, dying off easily leaving ugly brown spots. It is also quite susceptible to disease and can require regular fungicide treatment. Poa is light green in colour with soft leaves that often have a crinkly part. Because it is a grass itself it can at sometimes blend in and not be noticed at first. As it grows you will easily spot its lighter coloured scruffy tufts and white seed heads making your lawn look patchy.
How do I control it?
Prevention is the key to stop poa from invading, as few herbicides will control this weed selectively. As there are few herbicide options available for selective control of annual poa in fine turf, good cultural practices tend to be the best way of dealing with annual poa in such conditions. A strong, healthy lawn and well-rounded lawn care program will help to eventually eliminate it from your lawn. Techniques to relieve soil compaction and aerate the soil will help desirable species compete well with annual poa. Avoid providing more irrigation than is necessary in summer as this may assist annual poa.
Broadleaf weeds are a subset of plants that grow within your lawn that have wide flat leaves. The broadleaf weeds commonly found in New Zealand lawns include catsear, dandelion, thistles, dichondra, chickweed, creeping oxalis, docks, daisy, fat-hen, pearlwort, speedwells and hydrocotlye.
Any broadleaf weed that’s taking over your lawn has broad leaves. They are wide and flat and stand out from your lawn.
How do I control it?
Fortunately, several different herbicides will target broadleaf weeds in your garden without killing off your lawn. Some of these weeds look similar to each other but are quite different in how they respond to chemical control. The correct identification of the weed is the first step. It’s in your best interests to talk to gardening and lawn experts about what they would recommend. Each broadleaf weed will react differently to herbicides, and you must know which broadleaf weed you have.
Moss is a shallow-rooted weed that covers the ground and can be identified on your lawn as a spongy mat of low-growing greenery. Mosses don’t have true leaves, stems or roots and are rather simple plants with tissues that absorb moisture and nutrients. Although it can survive drought, moss needs moisture to grow so it is usually found where in shady spots drainage isn’t great, and/or there are low nutrient levels and acidic soil.
Moss isn’t overly invasive, but it can still be a nuisance lawn weed. If there is shade and moisture on your lawn, you’ll find moss nearby. It will cover the ground and lawn and be quite slippery to walk on. It also allows other more aggressive weeds to take hold. Moss also spreads quickly. Moss covers the ground with a spongy base and no leaves, roots, or stems. It absorbs moisture and nutrients from the bottom. When it dies, it leaves bald patches on your lawn.
How do I control it?
The first thing to understand is that moss grows in conditions that grasses do not enjoy. Mow grasses in shady areas on a higher setting. This will increase the amount of leaf exposed to all available sunlight. Mowing too closely reduces grass vigour, and so eventually moss and weeds will take over.
Moss can be sorted out short term by spraying, but if the issue is poor drainage or compacted soil, it would be wise to try and rectify this for long-term results.
Most common weeds can be treated with sprays, but the best solution varies depending on the type and ages of your lawn and variety of weeds and grasses present. During summer it can be very difficult to spray as rain is often needed to ensure the correct plants are taking up the correct dosage of the correct treatment.
Frequently Asked Questions
1. I have broadleaf in my lawn, how do I kill it without killing my lawn?
Fortunately, several different herbicides will target broadleaf weeds in your garden without killing off your lawn. Each broadleaf weed will react differently to herbicides, and you must know which broadleaf weed you have.
2. I think I have clover growing in my lawn, how do you suggest I treat it without harming the grass?
Clovers are an extremely common weed found in gardens throughout New Zealand. Clovers have creeping stems and distinctive leaves which are quite small and slightly notched at the tip. Selective herbicides will control this weed so talk to us to for the correct and effective solution.
3. What is a ‘selective’ and ‘non-selective’ herbicide?
Selective herbicides are used in lawn care or around nursery or garden plants once weeds emerge. A selective herbicide is used to kill weeds, but does not kill the valuable plant. Non-selective herbicides are the herbicide of choice for people who want to kill all vegetation in an area. These types of herbicides are generally used in building projects, near fences, driveways and within industrial complexes.
4. What about moss in the lawn?
Moss often develops because the grass is weak and lacks nutrients, conditions which often occur under trees or in moist places. This is often amplified during the winter months when cooler temperatures lock up soil nutrients and reduced sunlight hours weaken growth.
5. What plants are considered weeds?
A weed can be any plant growing where you don’t want it to, but there are some particularly weedy species to keep an eye out for. Weeds come in all sizes, shapes and growth forms, and are found everywhere, not just in your garden.
The biggest thing to ensure the long-term health of your lawn is the mowing technique. This may sound strange but topping your lawn regularly and not mowing too short will keep your lawn more weed-free. Having the grass taller makes it more difficult for shorter broadleaf weeds to establish themselves. Scalping the lawn (mowing too short) also makes the grass less resilient during dry weather and more prone to damage if crushed when frost is on it during the winter.