Weeds are an unfortunate byproduct of rainy weather
After all the rain we have had, it means more weeds. There are two major types of weeds. Annual weeds germinate from seed, grow for the spring or summer, form a flower, produce even more seeds and die. The winter annuals are growing and are mostly grasses. Common annual weeds include our spring grasses, crabgrass and foxtails.
The other type of common weeds are perennial weeds. They can start from seed, but they can go dormant in the winter and grow back from the roots or new seeds the following spring. Common perennial weeds include Bermuda grass and dandelions. Stinging nettle is a winter perennial and is becoming more common in the Antelope Valley.
There are three common ways to control weed seeds, especially annual weeds. One is to cultivate or pull out the weeds as they start growing. I find using a hula hoe is the best way to cultivate weeds, since you just slide at or below the soil surface.
Some weeds will grow back, but if you use the hula hoe again, you deplete the food stored in the roots and the weed does not come back.
The smaller the weeds the better, and they should be under a couple inches tall. A hula hoe is not a true hoe and you should never chop weeds like you would with a regular garden hoe. The more you disturb the soil, the more weeds can start to grow.
The second way is to spray the weeds with an herbicide as soon as they start growing. Both methods become an ongoing project throughout the year.
The third way is to use a pre-emergent herbicide. It builds a chemical barrier in the soil to prevent seeds from germinating and normally takes two to three weeks to develop a good barrier in the soil — which means the time to apply a pre-emergent herbicide is now, a few weeks before most of the weed seeds are germinating.
Most of the time, pre-emergent herbicide needs to be watered into the soil to work. You apply it now and hope the next storm helps to water-in the pre-emergent.
However, a pre-emergent herbicide cannot distinguish a weed seed from a flower or vegetable seed. This means you do not want to use it in areas where you plan to plant seeds. Pre-emergent herbicides will not kill weeds if the weeds are already growing. It only kills or prevents seeds from germinating.
A pre-emergent herbicide can be applied to your established lawn and landscape planters, especially if you are having a problem with crabgrass and spotted spurge. Crabgrass is a flat, wide leafed, grassy-looking weed. The stems easily root out into the soil at each joint.
Crabgrass is an annual summer weed, which means the seed germinates in the spring, the plant grows all summer and it dies at the first frost in fall. During its short life, each plant can produce thousands of seeds. Some germinate, that summer, but most lie on the ground all winter and germinate in early spring.
If you had a few crabgrass weeds, last year, you will have even more, this year. The best way to control crabgrass is to prevent the seed from germinating. Most garden shops carry either a pre-emergent herbicide or a weed and feed fertilizer that contains a weed preventer (pre-emergent herbicide).
Pre-emergent herbicides do not last forever and need to be re-applied according to the label. Generally, they last from three to 12 months, depending on the chemical nature. However, most of the general use pre-emergents found in local nurseries last only for four to six months.
A pre-emergent herbicide could also control the spotted spurge (Euphorbia maculata) that is also overrunning our landscape. It is an annual prostrate weed that grows in the shape of a circular mat arising from a single taproot.
Spotted spurge may have green or reddish leaves but are easily identified by a red spot in the center of the leaf. Another identifying characteristic is if the plant’s leaves or stems are cut, a milky white sap will appear.
Once the crabgrass has germinated, a pre-emergent herbicide will not kill the crabgrass. A post-emergent herbicide will be required. There are several herbicides that will kill crabgrass, but you must be very diligent in order to control the problem. Spotted spurge also will require a post-emergent herbicide after it germinates.
When it comes to herbicides or any pesticide, be sure to read the label very carefully. Make sure the pesticide will do what you expect and that you can safely apply it.