Weeds--the Gardener’s Enemy--Tough to Kill : Nuisance: Chemical products don’t work effectively against the four worst weeds. Best bet is a longtime, labor-intensive pulling by hand.
Three out of four of the world’s worst weeds are common in Southern California gardens, and if you include the San Joaquin Valley or places like Blythe, all four are present and accounted for.
Want to guess which weeds are the worst? If you thought nut grass, you’re right, though it is really “nut sedge,” since it is a sedge and not a grass.
Bermuda grass? You bet. And, bindweed. Number four, Johnson grass, is more of an agricultural weed though it has been found in gardens.
All of these are perennials, which means they come back year after year, spreading and conquering, which is why they are the worst. And all are found worldwide.
Nut sedge is perhaps the worst of the worst, making little “nutlets” or tubers underground. New ones form when the plant is still a youngster, right after it reaches the four- or five-leaf stage. It mostly spreads by these underground tubers since it seldom makes seed.
To make matters worse, these tubers may be as deep as 18 inches in the soil, though 6-8 inches is more typical. Dave Cudney, weed scientist at the UC Riverside, says that one way of dealing with nut sedge is to remove the soil to a depth of 18 inches, or more, and send it to a dump. If that is not feasible, the tactic is to starve nut sedge to death:
Pull up all the plants and then every time they try to come back, or new little plants appear, pull them out quickly, before they can make new tubers. Keep this up religiously for three years and you will probably be rid of it. Cudney calls this strategy “a holy crusade.”
Nut sedge often gets out of control when people go on summer vacation, which gives it just enough time to make new tubers. Be very wary from March through November, when it is actively growing, and keep pulling it out.
Little else will work. The herbicide Roundup will work partially but not completely, though it is difficult to treat just the nut sedge when it is among other plants; any spray falling on other plants will harm them more than the nut sedge, since most are more susceptible. As with all chemicals, read label precautions and directions carefully.
Cudney suggests one other means of control. He got rid of nut sedge in his back yard when he laid 4 inches of concrete dog run over a patch of it, but on campus he saw it break through a newly paved walk of asphalt. It’s one tough customer.
With this and all of these perennial weeds, he stresses that prevention is the best defense. Don’t let these perennials get started in your garden.
Keep an eye on any imported soil, and on newly arrived plants. Don’t spread them by putting them in the compost pile where their seeds will survive if the pile is not kept “hot” (which means it must be moist, deep, with added nitrogen and warm to the touch). In my own garden, I have two weed buckets--one for most of the weeds, which go in the compost pile, and one for these persistent perennial weeds, which gets emptied in the garbage.
Bindweed is next on the list of bad guys. It looks like a wild morning glory, with white cupped flowers and it twists around other plants in a vining fashion.
It spreads underground on bright white roots, and if you pull up part of it, it resprouts from the roots. It too can be partially controlled with Roundup, but this is difficult because the best time to apply the herbicide is just as the vine begins to flower, so the chemical is carried back to the roots (while the plant is growing, all materials are carried toward the tip of the plant, not toward the roots).
One way to apply Roundup on bindweed while avoiding other plants is with a sponge, wiping it on the leaves. Wear rubber gloves and follow all directions carefully, even though Roundup is considered a relatively “safe” herbicide.
Other than that, the best method is again starvation. Simply keep pulling it out promptly for about three years and it should give up, as long as there are no seeds present. Bindweed seeds can be dormant for 40 years.
By comparison, Bermuda grass looks easy to get rid of. It is very susceptible to Roundup though it too can come back here and there, or from seed. You can also try and dig it all out, but there are lots of rhizomes below ground and even a tiny bit left behind can resprout. But, keep after it and perhaps spot spray any stragglers with Roundup, and it can be vanquished. Do not chop it up with a power tiller or by spading or you will help it multiply quickly. On all of these but especially Bermudagrass--where there are not other roots (from trees or shrubs) in the soil--you can try fumigation. Vapam is available to homeowners, and if the directions are closely followed it works fairly well. Commercial pest control people can use methyl bromide, which is even more effective. Sometimes, however, the perennial parts of these weeds are too deep in the soil to be touched. Says Cudney “there is by no means a guarantee.” If you think you have number four on this list, Johnson grass, check if there are rhizomes underground as thick as your thumb. The grass itself is airy and graceful, quite tall, looking a lot like barnyard grass. Roundup works fairly well as a control, or dig it out.
Gardeners with these weeds undoubtedly wish there was a quick and sure fire control, but short of selling the house and moving on, control is only gained with persistence and patience--three to four years worth of both are required.
