Hi, Everyone. We are back with Part 2 of our look at common wet season (winter) weeds in Southern California. If you did not see Part 1, please take a moment to go take a look, we will wait for you.
Alright then. Let’s jump right in!
Chickweed (Stellaria media) is common in lawns during the winter. The mature plant can grow like a mat on the ground, covering a small area like a carpet. It reproduces mostly from seed, but it can also reproduce from creeping stems. Control should rely on hand weeding, hoeing, mulch, and solarization (if needed). It should be controlled before it flowers. It is important to not only remove the plant from the ground, but also remove it from the site, as it can reroot from the stem in moist areas. Proper water management is key as well, as this plant does not thrive in drier areas. Deep, infrequent watering discourages chickweed, including in lawns.
Chickweed flowers on a mature specimen
Common groundsel (Senecio vulgaris) is most common during cool, moist periods. Areas of over watering promote their growth during winter. They are toxic for humans and animals, over long periods of time or in large quantities.
They reproduce by seed. Proper water management and spot control (shallow hoeing and hand pulling), especially before they flower, help to control their spread. Mulch can also be very effective in control.
There are multiple types of common clover, and they tend cause problems in turfgrass. They can attract bees to their flowers, which is not a bad thing in and of itself, but cause problems for people playing on the lawn. Clover also diminishes the uniformity of lawns, and the mature burs of the burclover can become stuck on people’s clothes, or hurt them is they are walking barefoot. Clover can be controlled by hand pulling, hoeing, and mulch for planter areas. Their seeds have a hard cover, and they can germinate over many years, so control will be an ongoing effort. Lawn areas are more difficult to control clover. Increasing the nitrogen and having less phosphorus in turf can help. The best defense against clover is a thick lawn. Mowing will not control clover. Hand pulling before the clover seeds are formed. Hand pulling will need to be done repeatedly. Mulch layers need to be around 4’’ thick to effectively control clover in planters.
A grouping of white clover
Annual sowthistle (Sonchus oleraceaus) can have pests that damage nearby plants, and can look like dandelion.
It germinates in the top ½ inch of soil, so cultivation or solorization before planting can provide control. Mulching is also commonly effective against this plant, however spot treatment (hoeing and hand pulling) will be required.
Because the seeds are easily dispersed by wind, these weeds often germinate in decaying organic mulch.