Weeds and weed control

wally richards weekly column

A weed can be defined as a plant growing where you do not want it to grow. It maybe a preferred plant that has seeded or spread to become invasive, or it maybe a non desired plant that has made its home in your gardens.

I spoke to one gardener this week that had been told that horseradish makes a good companion plant so he had planted horseradish in several areas of his garden.
Horseradish spreads by its root system similar to convolvulus, couch and a number of other invasive weeds. This gardener now has a major problem trying to gain control.
Horseradish and mints are best grown in containers where they are secure in the pot. It is also advisable not to have the container in contact with the soil as they can creep out of the drainage holes to take over the area.

We often can cause our weed problems by our garden practices such as mowing our lawns when the grasses are in seed and placing the clippings in a compost bin or mulching onto our gardens.

Seed ridden compost, mulched or dug into gardens will produce a weeding problem for you later.
Recently a few gardeners have contacted me in regards to roses, tomatoes, beans and potatoes either dying or becoming mis-shaped in their new growth. (Feathery or distorted foliage) Some of these had applied green waste compost to their soils and this was why. Green waste compost is a great idea in recycling garden wastes but what happens at times, is some gardener sprays his lawn with a herbicide to kill the weeds and later when he mows the lawn the clippings are taken to a green recycle unit.
The operators have no idea that the clippings contain an active herbicide which will affect some plants in your garden such as roses, beans, tomatoes and potatoes.
The other cause of the distorted foliage on these plants was due to herbicide spray drift which could have resulted in the same gardener using Roundup or similar otherwise it would be another gardener somewhere in the area.

Often people believe that spraying on a calm day is best when in actual fact it is the worst time.
Minute droplets of spray are lifted by upward air currents and float along in the air in any direction to later fall somewhere. These could come from a mile away or from next door. When they land on say your tomato plants they cause damage. A good dose will kill the plant, a light dose will cause distortions in the new growth.

There should be a breeze at the time of spraying so you can direct your herbicide onto target plants and away from desired plants.

A simple safe proof way which allows you to spray on a windy day is to make a shield out of a two litre ice cream container by drilling a hole in the middle of the container at the right size to fit over the wand of the sprayer when the nozzle is removed. Place the end of the wand through the hole and then screw back on the nozzle.

You place the container over the weeds and give it a squirt of weed killer, beware of any dripping onto preferred plants.

This also prevents any upward drift of herbicide to affect your plants or your neighbors .
Another safety point is never use a sprayer for any purpose that any herbicide has been used in previously unless it is another herbicide you intend to use.
Some gardeners will not use a chemical herbicide on their sections and I am one of these.
We do weed control by the good old fashion method of hand weeding, have free range chickens in areas to clean up weeds or use salt, vinegar or oils for control.

For instance if you have a waste area or alternatively cobbles or similar, where weeds grow then good doses of salt will keep those areas free of weeds for sometime.

Sprays of vinegar or cooking type oils used on a sunny day when the ground is on the dry side will dehydrate the foliage of the weeds sprayed and in the case of annual weeds, kill them.
Perennial weeds will need further treatments or be pulled out. These sprays will also affect desired plants if you are not careful.

Another method is to use Sulphate of Ammonia which is 21% nitrogen and 23.6% sulphur, if this is sprinkled onto the centre of a weed such as a dandelion, dry and left dry it will burn out the crown.

Chemical herbicides are a quick way of controlling weeds and if you prefer to use them, then that is fine but remember that they are lethal chemicals and can cause you, children, pets and wildlife harm and health concerns. Full protective clothing should be warn and areas sprayed should have a no entry time for children and pets. This includes the same precautions when using glyphosate brands which includes the most common one, Roundup.

If you put Raingard into any herbicide you are using you will obtain better results.
Sometimes a combination of herbicides will work better for you if spraying different weeds. A combination of two or more such as say Woodyweed Killer and Roundup. Where Woodyweed Killer will not kill grass weeds, Roundup will but the Roundup may not affect some woody weeds for a absolute kill.

Here are a few more tips using herbicides:
If trying to kill an ivy cut the trunks coming out of the ground, a few inches up and cut again a few more inches off, so you can paint the stumps with a straight solution of Woodyweed Killer or Roundup.
The top foliage will die off in time and the chemicals should kill the root system. Any new shoots should be sprayed as soon as they appear.

Invasive weeds from next door can be sprayed  or it the case of  convolvulus you can make up a solution of say  Woodyweed Killer and Roundup and place them into a container or jar and then take the growing leaders of the weed and put them into the solution. The leaders will take up the solution and it will travel back over to next door wiping out an area of the weed.

Repeat this with every leader and you will solve a problem for sometime.
Gorse can be killed slowly with a heavy dose of garden lime applied to the root zone.
This is a method by which you alter the pH of the soil and thus it can become a hostile environment for some weeds or plants. The other way is to acidify the soil with good doses of sulphate of iron or similar which will control alkaline loving weeds. Beware that areas treated can also harm preferred plants.

There is a golden rule in weed control and that is every plant needs to obtain energy from the sun though their foliage, if you keep removing the foliage as soon as it appears eventually the weed has to fail.

Problems ring me at 0800 466464 (Palmerston North 3570606)

Editors Note: You may also like to look at for more information on problem weeds

2 comments on “Weeds and weed control

  1. Hi is it better to spray herbicide at dawn or dusk.

  2. First thing in the morning is better on a calm day without wind to avoid spray drift. This also means that the spray is taken up buy the plants during the day.

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