Pat Welsh Southwest Garden Advice, plus garden ideas for everyone » Weeds

Controlling Goathead Thorn

Pat — Sat, 19 Jun 2010 08:55:45 +0000

Question from Joy:
I live in El Cajon, Calif. We have a weed here that we call a “goathead”. Do you know what it actually is? and how I can get rid of them? We call use that name becaause the sticker looks like a rock with 2 horn. They are actually so sharp and tough they can flaten a bicycle tire.

Answer from Pat:
Goathead thorn or puncture plant (Tribulus terrestris) is about as noxious a weed as ever came down the track. (The common name comes from the shape of the seed heads.) So sorry to hear that you have it in El Cajon. If you have a dog, consider purchasing a stout pair of dog shoes for it. Some pet owners even muzzle their dogs to protect their mouths and noses when outdoors. The fact that a small, seemingly innocuous, weed can make thorns (and lots of them) stout enough to puncture a bicycle tire or even a car tire, may give readers a pretty clear idea of how much harm this plant can do to grazing animals, pets, or bare-footed humans.

Goathead thorn is native to the Old World but was accidentally introduced on animal fur and has now proliferated throughout the Southwestern states. Getting rid of it permanently on ranch lands may never be possible. Nonetheless, the department of Agriculture has already undertaken a concerted campaign of biological control by importing an insect called the puncture vine weevil to control it. Puncture vine weevils and other biological controls are available for sale to homeowners also. For more information, follow this link: http://www.goatheads.com/home/gh1/page_43_13/puncturevine_weevils.html

Both puncture vine stem weevils and puncture vine seed weevils are sold. If gardeners and farmers gang up on this weed we may be able to eradicate it from neighborhoods and perhaps eventuallywe’ll be able to control it on a larger scale throughout the west.

Another way of getting rid of this horrendous weed on a small scale is to burn it with a propane torch when you first see it in your yard, which effectively kills the plant and destroys the savage seedheads as well, but this solution is not permitted in many Western towns due to fire danger. (Before using a flame gun to destroy weeds, always investigate your local laws and restrictions or you may suffer a stiff fine.)

Still another organic way is to pull up the plants as soon as you see them and then press the area with a scrap of out-dated carpet one can obtain free from a carpet company to pick up any seeds that may have fallen to the ground. The seeds of goathead thorn were designed by nature to cling to the wool of animals, such as sheep and goats. They will grab and cling to a piece of carpet in the same way. Continue pulling up the plants and picking up the seeds in this way as soon as you see them, so you get those that have already been seeded. Weeding by hand really works but it takes persistence. Follow up by treating the ground with an organic pre-emergent such as Corn Gluten Meal to stop the seeds that the carpet missed, from germinating. Unfortunately seeds are long-lasting in the ground so you may need to stay vigilant for as long as seven years to get all that were accidentally introduced into your garden.

Fox tail

Pat — Tue, 27 Apr 2010 18:28:02 +0000

Question form Jake: Fox tail has taken over my lawn in the back yard. I have a grazing tortoise that lives back there so using toxic weed killer is out of the question. Is there any solution? What would you suggest?

Answer from Pat: Several grasses of the Alopecurus, Bromus, Hordeum, and Setaria genuses share the common name of “foxtail grass” or “spear grass”. I don’t know which one you have, but all are hazardous to animals. Wall barley or false barley (Hordeum murinum), is one of the worst. All of the foxtail grasses endanger longhaired dogs and many other animals since they become entangled in the animals’ hair, traveling through it and finally piercing through the skin into the flesh and also into animals’ ears, noses, and eyes. These foxtails cause miserable pain and suffering to animals and even in some cases they can cause death. Whereas turtles don’t have hair, foxtail grasses, bromes, barleys, and millets can all get up under the legs of turtles, under the shell, and enter their flesh, causing inflammation and disease. They can also be dangerous if ingested.

My recommendation is first to treat all the clumps of foxtail with a non-chemical, non-poisonous weed killer. One possibility is to use straight vinegar (a strong but non-poisonous acid.) Simply pour it on the roots of the plants. Another suggestion is to use human urine (a strong but non-poisonous alkaline.) Pee in a bucket and pour it straight onto the roots. You know how dogs can cause unsightly spots on your lawn. Well, use that technology yourself by doing the same. You may find this advice off-putting but this solution is free. It costs nothing and furthermore it is safe.

You need to get rid of the foxtails as quickly as possible so they don’t reseed. So, after using an organic weed killer of your choice to kill all the foxtail grass, then pull out or hoe out the clumps, bag them and send them to the dump. or use a mower or weedwacker to mow off all their tops along with their flowering heads. (If you can see the flowering heads of the foxtails your lawn must be way too long and maybe too tall to use an ordinary mower, so that’s why I suggested a weed wacker.) Do not compost the remains these since the seeds will find any way they can to proliferate. The chances are your compost won’t be hot enough to destroy them. So bag the dead plants and send them to the trash. Check the lawn after mowing and rake it carefully to make sure you have removed all the heads.

After mowing, continue treating with your organic weed killer until all the clumps have turned straw-colored and are completely dead. Then pull or hoe them out. A long-handled, goose-hook weeder works well for this job. If you used the alkaline method you can balance the soil again by applying the acid solution. If you used the acid method, straighten it out with the alkaline and water it in. (A soil test will tell you if you succeeded, but many gardeners just pour a little vinegar on spots made by dogs and then water it in.)

Reseed the lawn with an appropriate grass for your area or replace with sod. (See the Lawn section in the monthly chapter for March in my organic book beginning on page 129 for ideas for drought-resistant lawn grasses.) Once you have renewed your lawn, fertilize it regularly to keep it growing thickly so weeds won’t invade it. Also, treat it once or twice a year with an organic pre-emergent herbicide such as Corn Gluten Meal to keep the weed seeds from germinating, but don’t do this prior to seeding or of course your new lawn won’t grow.

Self-Sowers & Plant Volunteers

Pat — Wed, 03 Feb 2010 09:25:57 +0000

I once asked my gardener Raymundo why he never weeds. “Because in your garden, Senora,” he replied, “you can ‘t tell the difference between a weed and a flower!”

He had notice d that in our mild Southern California climate many garden plants are self-sowers, plants that drop fertile seeds which germinate to become “volunteers,”little gifts of nature springing up in places where we may or may not want them. For example, many years ago in March or April I brought home from the nursery a 4-inch-size potted plant. It’s bright green, feathery foliage was dotted with neat little daisies with white petals and yellow centers, like a miniature marguerite. “Paludosum daisy (Chrysanthemum paludosum)” said the tag. Having heard it was a good choice for edging beds, I popped the little plant into the ground on the edge of a flowerbed where it quickly expanded to about a foot high and wide, bloomed its head off for six weeks and promptly died. “What a dud!” I thought. This remained my opinion until the following fall, when all over the garden hundreds of little paludosum daisies popped out of the ground. In January they began to bloom and continued flowering through winter into spring. All I had to do was weed them out of areas where I didn’t want them, thin them out where they grew to thickly, and move a few to other places. Thus I was introduced to joys of the self-sowers, those generous plants that sprout from seeds they or the birds sow in your garden year after year. Chrysanthemum paludosum (or Leucanthemum paludosum, as it is now called) is a short-lived, cool-season annual and such an avid self-sower that I have never needed to purchase another.

Self-sowers can be can be native or exotic. They can be annual, biennial, or herbaceous perennial. They may also be woody plants, such as trees, shrubs, and climbers. In mild-winter zones we plant the cool-season annual and perennial flowers in fall so that we can enjoy their flowers all winter into spring, and warm-season annuals and perennials in late spring to enjoy them in summer and fall. But when working with self-sowers the gardener doesn’t need to worry about timing. Each seed will sprout at the right time of year for that particular species in a specific garden depending on where it is. Factors impacting germination include soil temperature, day-length, light, the amount of rainfall or irrigation, and climate zone. Because all these factors vary, seeds that sprout easily in my garden might not be the same ones that sprout in yours. Cerinthe major, for example, won’t germinate in my garden, but a few miles inland it germinates and comes back year after year.

Throughout the Southwest many wildflowers such as Mexican hat (Ratibida) will come back year after year once established. Mexican hat has two methods of self propagation since once planted it is perennial but it also comes up from seeds. I know a patch in a hot dry roadside location outside a garden wall where it was planted over 15 years ago and it still comes up every year.

African scurf-pea (Psoralea pinnata) is a rare, short-lived shrub or small tree with feathery foliage and leaning trunk, blanketed in late spring with small, fragrant, azure-blue to violet, pea-shaped blooms with white wings. Riparian in its native habitat, it’s become a pest in moist parts of Australia. In Southern California it survives occasional drought in gardens, but not in the wild. Provide good drainage and prune hard after bloom. For tree shape, prune to the most upright leader. When plants eventually die, they leave ample progeny and straight branches useful for garden stakes. For knock-out color contrast, plant with azaleas and camellias; they bloom at the same time.

Madeira geranium (Geranium maderense), a biennial or sometimes triennial, is the largest botanical geranium and seldom found in nurseries. This astounding plant has large deeply cut leaves and produces an enormous central inflorescence, three-feet across, composed of hundreds of deep pink, magenta-centered blossoms. Flowering lasts March through April, then the plant dies leaving many seeds that germinate in October. You’ll have plenty to grow and share. Never cut off leaves; their stems bend down to support the plant and store starches that feed the huge inflorescence. If you need to move plants, do so before winter solstice or they won’t bloom. Protect from frost and give each plant a big handful of slow-release 14-14-14 fertilizer prior to a late winter or early-spring rain.

Despite their easy care virtues, garden plants that sow themselves share the ability to survive with many weeds, so it’s wise to grow them in conjunction with a few rules. One wise rule says “Any plant growing where it is not wanted is a weed.” This is particularly true with trees. Torrey pine, Victorian box, Washingtonia palms, Monterey cypress, and floss silk tree (Chorisia speciosa) are just a few of the trees whose seeds self-sow in my mild coastal climate zone. In interior climate zones other trees will germinate, such as deciduous fruit trees. Occasionally, a chance seedling may become a famous variety, such as the Gordon apple, but most are useless. Some self-sown ornamental trees are garden treasures. Seedlings of Japanese maples are worth potting-up as gifts for friends since they often turn out to be far hardier specimens than fancy varieties bought in nurseries. But if gardeners fail to weed out all unwanted trees and shrubs like Pride of Madiera, and climbers like honeysuckle, their gardens will soon become over-shaded jungles.

Some plants are so generous with their seeds that weeding them out where they’re not wanted may be a problem. Among our loveliest perennials, Santa Barbara daisy (Erigeron karvinskianus), butterfly verbena (Verbena bonariensis), and common gaura (Gaura lindheimeri) share the weedy habit of spreading throughout the garden. Others such as annual borage and the biennials, foxglove (Digitalis) and Madeira geranium (Geranium maderense) are easy to pull out or share with friends. Columbine (Aquilegia) usually isn’t perennial in mild zones, but if you leave the ground undisturbed until late winter or early spring you may find a little circle of baby plants right around where the parent grew. Dig them up and plant them where you want them. Other plants sow themselves so avidly and are so tenacious once established that you should think twice about planting them the spectacular orange Peruvian lily (Alstroemeria aurea) and fortnight lily (Dietes iridioides) are like this, spreading both from roots and seeds. Beware the fashionable grasses, some of which plant themselves into wild lands. Pampas grass (Cortaderia selloana) and common fountain grass (Pennisetum setaceum) are well-known pests that have become impossible to eradicate. Now other exotic grasses including eulalia (Miscanthus), fountain grass (Calamagrostis), sea oats (Chasmanthium), and the lovely Natal ruby grass (Rhynchelytrum) are escaping from gardens and spreading into the wild. Some exotic wildflowers, such as crown daisy (Chrysanthemum coranarium), too, have been criticized for invading the wild, but crown daisy is mainly a roadside plant and cannot survive amidst chaparral.

Some self-seeders, such as nasturtium (Tropaeolum), are easy to pull out when they sprout where you don’t want them. The problem with nasturtiums is that compact types revert to climbers. You may plant elegant varieties one year and end up with rank climbers ever after whose large leaves hide the jolly flowers. I have this type, but since the leaves look rather like lily pads and I have reached that happy age when I can garden for my own pleasure and not for what other people think, I don’t mind as much as I used to. My advice is enjoy the self-seeders with gratefulness for their bounty but with an equal measure of caution. If you stay away from the trouble-makers, the others will make your gardening life much easier.

Pernicious Weeds

Pat — Thu, 03 Dec 2009 05:54:41 +0000

In my opinion the three most pernicious weeds in this area are common Bermuda grass (Cynodon dactylon), purple or yellow nutsedge (Cyperus sp.) and creeping oxalis (Oxalis stricta and O. corniculata). I choose these three is because they seem most difficult to get rid of. Chemical controls are available for all these problems, and if properly applied according to package directions may offer success. However for the organic gardener, non-toxic controls may be the only choice.

In Southern California mulching, hoeing, and handpulling are the three best ways to control most weeds in the home garden. A thick layer of organic mulch is additionally beneficial since it helps retain water and as it breaks down it can improve fertility of the soil. However, in the case of Bermuda grass, it will grow up through mulch, no matter how thickly it is applied. Hand pulling is also an ineffective control for Bermuda grass because the roots create stolons which cannot be pulled out. Thus hand-pulling only increases the proliferation of this weed. This is true also with nutsedges but for a different reason. Nutsedges produce tubers on the roots. When you pull off the tops, the tubers stay in the ground to re-sprout. However, in the case of nutsedges, repeated pulling will eventually weaken the tubers. It is possible to win in the end by sticking it out and pulling repeatedly, but this requires great vigilance.

A better system for getting rid of both Bermuda grass and nutsedge is to use shade. Neither of these weeds can grow in solid shade, such as can be provided by black plastic or a layer of newspapers covered in both cases with mulch. When using black plastic or newspapers, be aware that irrigation water may not sufficiently penetrate newspaper and thus drip systems had better be installed beneath the plastic or newpaper. When water is from rainfall or above-ground irrigations systems, a better solution is to apply the shade by putting down a layer of landscape weed cloth that is permeable by water and then covering it with a thick layer of mulch. A fine-textured landscape, weed-barrier, cloth allows water to penetrate, but it will not allow most weeds to get through it. Make x’s in the landscape cloth through which to plant your permanent shrubs, vegetables, or flowers. In flower gardens and shrubberies this system will work well to kill off nutsedges. However, Bermuda grass will travel long distances under the barrier and try to sneak out the ends. In these cases, try treating the escaping stems with white vinegar. Or repeatedly pulling, or bending the stems down and covering with more cloth, thus cutting off all light. Solid shade will eventually kill off the Bermuda grass, but the system takes time and assiduous watchfulness.

Several kinds of oxalis are pests in the garden, some of which also make tubers, thus making them more difficult to control. Pulling oxalis repeatedly and adding organic mulch around plants are probably the least toxic and most effective ways of keeping it under control in flowerbeds. In walls, and cracks between pavement, try spraying with white vinegar. White vinegar can also be used to spot-treat weeds in lawns. A strong solution of urea and water will also kill weeds when used as a spot-treatment in lawns, in cracks in pavement, or in walls, in the same way that dog urine will kill out a little patch of lawn. In lawns, it will take a while for the spot to heal up, so after the weed has died, follow up with water and gypsum to help wash the vinegar or fertilizer away and then put in a plug of fresh grass.

There is one other non-toxic way to get rid of weeds, which is soil-solarization (wetting the ground and covering with clear plastic in full sun during a whole season.) If your whole sunny garden is overrun with any one of the above weeds, you may never be able to get rid of it without resorting to soil-solarization over the entire area it infests. This method will kill off most or all weed seeds and tubers, but it is likely that they will return eventually from seeds brought in by birds or blown in by the wind or in the soil mix of nursery plants. It should also be noted that whereas soil-solarization gets rid of harmful pests and diseases such as nematodes, white grubs, and harmful fungi, it also kills many beneficial organisms such as beneficial nematodes, earthworms, and bacteria in the soil including rhizobia, that increase fertility by adding nitrogen to the soil. Thus the shade method is safer and in the long run more effective.