Can anyone in the Melbourne area help a reader who needs plants of the weed known as Cobblers Pegs, Farmers’ Friend, or Black Jack, for medicinal purposes?
This common, widespread weed (Bidens pilosa), with its spiky seeds that attach themselves to gardeners’ clothing, has a long history of use in complementary medicine. This lady requires the plants to make tea from the leaves. She does not drive and is having trouble finding them locally.
If you can help, please contact me by email or comment, and I will forward her email address.
Early winter is the time to eradicate this weed pest, although I’ve noticed young growth of this weed in May on the Mid North Coast of NSW. Bindii (Soliva pterosperma), or “Jo-Jo” as it is called in some places, or “onehunga” in New Zealand, is a delicate-looking lawn weed that produces carrot-top or ferny foliage.
In late winter and early spring, each branch produces a rosette of spiky seed heads that detach from the rosette into individual seeds with a sharp spine that attach themselves to the soles of shoes, and make walking barefoot or sitting on grass a painful experience. By the time the plants produce seed heads, the branches will also produce roots from stem joints and removal is difficult. For successful removal this diabolical weed has to be eliminated before the seed heads form. From now until the end of June is a great time for action, in any moon phase if seed heads haven’t formed.
If you don’t have a steam or flame weeder, young plants are easy to dig out in early winter if you only have a light infestation. For more wide-spread infestations, the good news is that several companies have produced certified-organic weed sprays. Certified-organic weed sprays
Spot-spraying with Yates ‘Nature’s Way Weed Spray’ or Organic Crop Protectant’s ‘Slasher’ will burn off the weeds, while Organix’s ‘Weed Blitz’ works by removing the outer coating of foliage and seeds, causing cells to collapse. A Google search will direct you to a local supplier.
Bindii is more common where lawns are undernourished. Vigorous lawns usually out-compete this weed. To avoid future problems, in late winter, water the lawn and fertilise with organic complete fertiliser and seaweed extract tea, and do not mow the lawn too short as this weakens lawn growth – raise the mower a notch or two. Dynamic Lifter granules are easy to apply to lawns.
July and August are ideal months to get a head start on weed control. Last Quarter phase is a good phase for weeding because seed germination tends to be lower then, and you are less likely to stimulate further weed seed germination while removing weeds. Many weeds that germinate in cultivated soil are and pests that damage vegetable crops. July is too late to eliminate the lawn weed Bindii as the spiky seed heads will be starting to form.
You can find organic treatments for troublesome weeds in the ‘Weeding Between the Lines’ category on this blog.
Last October I updated the warning about pyridine herbicides that can damage or kill both food crops and decorative plants. Unfortunately, some readers have since had plant damage after inadvertently purchasing manures or mulch that contain one of these herbicides, despite a NSW government website stating that no damage has occurred in Australia.
As a result, I am posting a reminder.
Pyridine herbicides are only effective on broad-leaf plants, but the chemicals remain active in mulch cut from sprayed pastures and in manure from animals that have grazed on sprayed pastures until the chemicals are broken down by soil microbes. Of particular concern to home gardeners and councils that recycle waste into compost for agricultural and domestic use are the products containing aminopyralid, clopyralid and picloram because they are quite persistent, and residue from these herbicides can damage plants for up to 24 months. However, because the Australian Pesticides and Veterinary Medicines Authority (APVMA) regards the person who sprays the herbicide as the ‘end user of the product’, any warnings are limited to product labels without any regard for unsuspecting gardeners who, in good faith, purchase mulch, compost or manures contaminated with the herbicide, and who may not recognise the cause of the damage to their crops because they have not personally used any herbicides.
A recent check of their website shows that the APVMA has registered 233 herbicides that contain at least one of the pyridine group of herbicides – an impossible list to check through before purchasing mulches, manures or compost. The entire tomato family, lettuces, sunflowers, spinach, strawberries and legumes are particularly susceptible to damage from these herbicides, which can also affect a range of ornamental plants. To protect your garden from pyridine herbicide damage: only use aerobically composted manures on gardens. Aerobic composting requires weekly turning or stirring to ensure the composting process is carried out by microbes that require oxygen. Breakdown of the herbicide will be very slow in compost heaps that are not aerated.
Mulch that carries an organic-registered label does NOT contain any herbicides. Mulches from uncertified sources are high-risk products because the drying and baling of mulch materials eliminates microbial action, and the herbicide will still be active. The only safe compost to purchase is organic-registered compost.
If you are unable to purchase certified-organic manures or mulch, test the safety of the product by sowing some seasonally suitable peas or beans in pots containing certified-organic potting mix (with the manure mixed through it) or covered with the purchased mulch. (Water this pot through the mulch). Keep the test pots well-watered to eliminate other sources of stress. You should be able to see if an input is contaminated within 21-28 days. Dispose of any affected plants and potting mix with household garbage. Symptoms to look for are: Poor germination or death of seedlings, twisted, cupped or elongated leaves and twisted growth, misshapen pods.
Return remaining contaminated inputs to your supplier. If this is not an option, aerobic composting is the quickest way to break down these herbicides. Test the mature compost for herbicide residue.
If you find that the mulch has been affected, use it on beds that you can leave fallow until aerobic microbes in topsoil break down the herbicide or, if space is limited, compost it aerobically. if you find that garden beds have been affected, dig organic-registered compost through the bed and keep it damp to keep soil microorganisms breaking down the herbicide as quickly as possible.
Notify your supplier of the problem as pyridine herbicide product labels state that treated crops are not to be used for hay, silage or animal bedding, and manures are not to be spread on land used for growing susceptible crops.
Please also take a minute or two to notify the APVMA of problems with these herbicides. The APVMA encourage the public to report pesticide problems through their new Adverse Experience Reporting Program (AERP) by e-mail: email@example.com, phone 1800 700 583, or fax: 612 6210 4813.
You can find Australian product names of these herbicides by going to the APVMA’s Public information (PUBCRIS) page. Under product type select ‘herbicide’, then type aminopyralid, clopyralid or picloram in the active constituent panel. Click ‘Search’.
The NSW Government has been aware of the problems with these herbicides in Australia since 2005.
This is a good time of year to get a head start on weeding, as no-one likes weeding in hot weather. Leather gardening gloves or rigger’s gloves are great for weeding because they provide good protection from thorns, prickly stems, sharp edges of leaf blades, and insect or spider bites.
Weeds in the vegetable garden don’t just steal water and nutrients from your crops, many are also hosts to pests and/or diseases that can spread to your vegetables. By hosting diseases, weeds undermine your work at crop rotation to keep soil healthy.
Newly germinated weeds can be removed with a shuffle hoe, left on the bed surface, and covered with mulch. They will break down to return organic matter to topsoil. Small weeds that have not formed seed heads and are disease-free can be composted or put into worm farms. Larger weeds with seed heads must be removed and destroyed by burning, or soaking in water for an extended period, or disposed of in a sealed plastic bag. Remember the adage “One year’s seeds equals seven year’s weeds” – 15 years in some cases.
For gardening advice on removing troublesome perennial grasses and bulbous weeds, see my post on perennial weeds.
Nightshade (Solanum spp.)
The nightshade weeds are members of the same family as tomatoes, potatoes, capsicum and eggplant. Nightshade weeds (and Buffalo/Noogoora Burr) are hosts to Rhizoctonia fungi that can damage potato plants and tubers; cause collar rot in many plants, and cause damping-off in seedlings. They also provide a host to verticillium wilt that can affect a wide range of vegetables, fruit trees and ornamentals. Black Nightshade is a common weed in gardens. It grows to about 120 cm high, has groups of white (or purple-tinged) star-shaped flowers with a ring of 5 bright yellow stamens in the centre, and small green berries that blacken as they mature. Birds spread this weed by eating the berries.
Cobblers pegs (Bidens pilosa) This weed is also known in Australia as ‘farmer’s friends’ because the barbs at the end of seeds allow the masses of seeds to cling to clothing and animal fur. Each plant produces hundreds of seeds and this weed can grow into dense stands that can quickly fill an entire bed. It is a host for root knot nematodes, tomato spotted wilt, and sclerotinia rot that can affect many crop plants. Remove and destroy these weeds while they are very small.
Broad-leaf weed killers that contain the pyridine herbicides have caused widespread damage to many gardens in New Zealand, the UK and the US in recent years, and these herbicides are now being sold in Australia.
Pyridine herbicides include aminopyralid, clopyralid, fluroxypyr, picloram, and triclopyr. They are only effective on broad-leaf plants, but the chemicals remain active in mulch cut from sprayed pastures and in manure from animals that have grazed on sprayed pastures until the chemicals are broken down by soil microbes. Of particular concern to home gardeners and councils that recycle waste into compost for agricultural and domestic use are the products containing aminopyralid, clopyralid and picloram because they are quite persistent in compost (particularly anaerobic compost), and residue from these herbicides can damage crops for up to 24 months.
Is it just me, or do other people think it is crazy that there is widespread concern about the future of food production in Australia, and all levels of government are advising us to recycle and store carbon, yet the Australian Pesticide and Veterinary Medicines Authority (APVMA) continues to register more and more of these herbicides that damage food crops, and little if anything is being done to warn the public of the risk in using mulches, composts or manures contaminated by these herbicides.
Although there are only two pyridine herbicides containing aminopyralid (Hotshot and Grazon Extra), the APVMA has registered 59 herbicides containing clopyralid, 54 containing picloram, 27 containing fluroxypyr, and 77 containing triclorpyr, and there are several more of these herbicides awaiting approval – an impossible list to remember when purchasing mulches, manures or compost.
The problem with Australian regulating authorities is that they regard the person who sprays the herbicide as the ‘end user of the product’ and any warnings are limited to product labels without any regard for the unsuspecting gardeners who, in good faith, purchase mulch, compost or manures contaminated with the herbicide, and who may not recognise the cause of the damage to their crops because they have not personally used any herbicides.
Around this time of year, a lot of gardeners seek answers from gardening gurus, books and the internet to their onion weed or bindii problem.
Treating onion weed and oxalis with glyphosate will only kill the parent bulb – not the tiny bulbs that are loosely attached to the base of the main bulb. Onion weed also tends to be resistant to normal strength herbicides and gardeners have said that they have to use undiluted glyphosate. In garden beds, this can create other problems. Glyphosate is not broken down on contact with soil. It binds to certain soil compounds. When soil conditions change, it can become unbound and affect later crops. Soil-borne plant diseases are also more common where herbicides are used. Get Rid of Onion Weed
For an effective way to rid your garden of onion weed, see Onion weed treatment Get rid of Bindii
Bindii or Jo-jo needs to be treated in early winter before the vicious spiky seed heads form. It is far more difficult to eradicate this weed later in the season, see Bindii or Jo-jo
Onion weed (Nothoscordum inodorum) seems to cause problems for quite a few gardeners who are unsure about organic ways to be rid of this pest. I did cover onion weed previuosly in a post on perennial weeds but, as it is a common problem, it might be worth covering it separately.
It is fairly easy to eradicate it from lawns, by keeping grass growing vigorously. Healthy lawn grass will out-compete onion weed in a fairly short time and no other treatment is necessary. In fact, onion weed in lawns is merely a sign that your lawn needs a bit more TLC.
Onion weed in garden areas is an entirely different problem. Because onion weed is a perennial weed, it stores nutrients and carbohydrates in its bulbs to generate growth in the following season, in the same way as spring bulbs such as daffodils. Trying to pull out or dig up these weeds in garden areas results in the parent bulbs releasing tiny bulbs (bulbils) from the base of the main bulb. These grow into mature plants, and all the digging has achieved is multiplication of the problem. To get rid of onion weed, you have to prevent the bulbs storing food for growth. Onion weed can also produce seed. Cutting off the foliage at ground level will prevent the plants making carbohydrates in their leaves, and also prevent seed forming.
In an unused garden area, you can do this by slashing, or mowing, the foliage to ground level, then covering the area with black plastic for several months. Anchor the edges of the plastic with planks, bricks or whatever you have to prevent it blowing away. Deprived of moisture and the sunlight that enables it to store carbon dioxide as carbohydrates (photosynthesis), the bulbs will weaken and die. Avoid using clear or light plastic, as these will still allow the plants to photosynthesize and, in some conditions, they can actually improve weed growth.
In garden beds that are being used, onion weed is more difficult to eradicate because the bulbils can be released whenever you disturb the soil. Cut off the foliage at ground level with shears to prevent it making food for the bulbs. Then mulch the beds with 5–7 cm of mulch. You may have to cut back foliage several times as soon as it appears. If you do this consistently, bulb growth will become progressively weaker, and you will eliminate the problem without disturbing the soil and stimulating the growth of more bulbs.
When you have a chance to leave a particular bed lying fallow, you can give the bed the black plastic treatment. Onion weed is more commonly found in undernourished soils, or where soil pH is unsuitable for healthy plant growth. Where onion weed has been a problem, check your soil pH, and improve organic matter content in soil to prevent the problem recurring.
In order to eradicate problem weeds, including Nut Grass, Onion Weed, Sour-sob (Oxalis), and Tradescantia (Wandering Jew/Creeping Jesus), it is necessary to understand how these plants reproduce, because merely digging, or pulling out, these weeds is rarely successful. Wandering Jew or Creeping Jesus is a weed of moist, shaded places. It produces extra roots at the stem joints where they touch the ground. The stems snap easily when pulled, allowing small pieces of stem to remain in soil and produce new plants, making it difficult to completely eleiminate in one go.
You can tackle this weed by whipper-snipping or cutting off as much above ground growth as possible. Rake it up and dispose of it in a sealed plastic bag. Then cover the area with black plastic or weed mat anchored around the edges. It likes damp soil, so the black plastic is best – it will prevent rain getting to the soil. Excluding light also prevents the plants from manufacturing food for future growth. Then, the most important part is to go around the outer edges of the plastic with a sharp spade and cut through any underground runners that may be extending beyond the plastic, otherwise these parts will keep supplying the runners under the plastic with food and moisture to grow. It can take up to a couple of months to kill off this weed.
Nut grass, onion weed, and Oxalis or Sour-sob release small bulbs (bulbils) into the soil when plants are pulled out, or when soil is disturbed by digging, which rapidly increases the number of weeds. During each growing season, these weeds use sunlight, carbon dioxide and water to manufacture glucose to use for energy. The glucose is stored in the bulbs and bulbils during a period of dormancy to be used for growth in the next season (in the same way as spring flowering bulbs).
The way to eliminate this type of weed is to prevent them manufacturing food through the green parts of the plant. This can be done by excluding light and water for a couple of months with thick cardboard or black plastic. If these weeds are a problem where they are close to plants, repeatedly cutting off the foliage at ground level will eliminate them.
If they are growing in a lawn area, improve fertilisation and watering of the lawn. A healthy, vigorous lawn will smother these weeds.
If you want to convert some of your lawn to a garden, the obvious first step is to get rid of the grass. This is easier said than done with Couch and Kikuyu. Any pieces of runner left in the soil will re-shoot and become a pest in your garden beds. Lawn grasses are perennial, which means they are long-lived and able to regrow from stored nutrients after a period of dormancy.
All green plants require sunlight, carbon dioxide and water to manufacture glucose that they use for energy, and we have to deprive them of these in order to kill the grass without using poisons. You can exclude light with pieces of thick cardboard, a very thick layer of mulch, or a sheet of black plastic. I’ve found black plastic works best because it absorbs heat and speeds the process. Clear or white plastic won’t exclude light, and can actually increase growth in some conditions. The light-excluding cover will have to be weighted around the edges with some stones or scraps of timber. Now comes the most important step. Go around the outer edge of the plastic with a sharp spade and cut through the grass runners. If you don’t do this, the runners outside the plastic can keep supplying water and glucose to the covered grass, and it won’t die off.
The time taken to kill the grass will vary according to the climate. In warm, dry conditions it can be completely killed off in 4–6 weeks. The dead grass and roots will break down to provide valuable organic matter to soil.
Avoid using herbicides to kill the grass. Recent research published by the US Department of Agriculture has shown that glyphosate can stimulate the growth of Fusarium Wilt pathogens in soil. This disease can affect many food crops, and is difficult to eliminate once established.