Weeding out the bad | January 18, 2019 | Palo Alto Weekly | Palo Alto Online |

Palo Alto Weekly

Real Estate - January 18, 2019

Weeding out the bad

Rainy winter days are perfect for ousting plants you don't want

by Elizabeth Lorenz

The good news is that in winter, your yard tends to look greener from far away, even if up close that low-growing green carpet is really a patch of weed sprouts.

The bad news, according to Master Gardener Rebecca Schoenenberger, is if you don't deal with those weeds now, you will see the 3-foot feisty deep-rooted version in your lawn in spring.

Schoenenberger, who also owns landscape design company California Nativescapes, teaches a workshop on weeds and weeding through the UC Extension's master gardener program.

That green mist in your yard, she said, is actually sending you some warnings: Controlling us is an ongoing gardening activity (pencil us in on your calendar); a single weed produces 223,200 to 250,000 seeds per plant each season; we have uneven germination of our seeds. In other words, not all seeds will germinate when conditions are favorable (some will remain dormant until the next season).

Schoenenberger teaches her students to slowly ratchet up their battle plans as the need progresses. Stop the seed cycle by pulling or removing weeds as soon as possible. Don't move weeds around from unknown places. Plant beneficial plants densely to suppress weeds. Use mulch on blank spots to prevent weed growth.

Every garden is different and so are gardeners. Some swear by one thing and others another.

"I find weed cloth can be more effective in rock or cactus gardens, where you don't necessarily care about building up healthy soil," she said. She generally warns against using the black or gray fabric in a traditional garden because the sun still shines through it.

With a lawn, she said, "It kind of depends on what's coming up." Annual grasses in a lawn will just die off. Most lawns usually come in a blend of fescue and rye (90-10), she said. "What often happens, most people let everything grow, and the landscapers mow it down."

One approach to killing weeds if you have a larger area to work with, she said, is "sheet mulching," which can be done any time of year, but right now is the easiest time to see the weeds because they are green and small.

She recommends taking something solid, like cardboard, newspaper, clothing, or even "a bunch of junky T-shirts," and laying them out over the patch of weeds, overlapping the material a bit on each edge.

If you can get cardboard rolls, they are the easiest to lay out, she said. The solid material will prevent photosynthesis. Put about 2 inches of mulch on top of the cardboard.

Why should you remove weeds? Mainly because they will compete with your more valued plants for nutrients, water and space, she said.

"Weeding now is best because the ground is super soft," Schoenenberger said, boasting that just that day, she pulled out a huge dandelion by hand.

"Think of weeding as therapy," she said, and take out your aggressions on the weeds. "It's actually really rewarding to see the difference after. Take a before and after picture to make yourself feel better and see what a good job you did."

If she needs a tool to pull weeds, she uses a "hori hori," also known as a soil knife, to do the job.

She agrees that sometimes one person's weed is another's native plant. She cites an old book called "Weeds of the West," which is actually full of what today's gardeners would call beneficial native plants.

If you consider fungi, such as mushrooms, to be weeds, Schoenenberger said to pick them as soon as you see them and as fresh as possible before they have a chance to drop spores, especially if you have pets. But if you don't mind leaving them, mushrooms do serve as your garden's "decomposers," eating old tree stumps and roots.

The critical thing, she said, is catching weeds as they start to grow. As the days start warming, it's important to take out particularly aggressive weeds like foxtails (also called foxtail barley) early to stop the weed-to-seed cycle.

While Schoenenberger, the master gardener program, and UC's Integrated Pest Management program all advocate for gradual levels of removal, she said in some cases, a pre-emergent spray (which prevents weeds from growing) or a post-emergent one may be called for. She cautions gardeners to read chemical labels very carefully, cover skin and wear respiratory protection. All of the chemicals sold in nurseries, she points out, are "legally safe."

If you can clear out the seeds, or even go ahead and "whack" tall weeds down with a tool, those should be done first.

Once that's done, the easiest thing is to add a good layer of mulch. Mulch can be anything from bags from a nursery to tree chippings. Some local garbage companies also make chips from old wood pallets and other wood products and offer them as mulch.


1. Purslane — Portulaca oleracea (summer annual broadleaf)

2. Burclover — Medicago polymorpha (annual broadleaf)

3. Cheeseweed (Mallow) — Malva parviflora (winter annual broadleaf)

4. Fillaree — Erodium spp. (winter annual & sometimes Bienniel)

5. Crabgrass — Digitaria spp. (annual grass)

6. Bluegrass — Poa annua (winter annual grass)

7. Dandelion — Taraxacum officinale (simple perennial)

8. Bermudagrass — Cynodon dactylon (creeping perennial)

9. Bermuda Buttercup — Oxalis pes-caprae (bulbing perennial)

10. Wood Sorrel — Oxalis corniculata (creeping perennial)

11. Nutsedge — Cyperus spp. (bulbing perennial)

12. Burning Nettle — Urtica urens (annual broadleaf)

Stinging Nettle — Urtica dioica (annual broadleaf)

13. Scarlet Pimpernel — Anagallis arvensis (winter or summer annual)

14. Puncturevine — Tribuls terrestris (summer annual)

15. Field Bindweed — Convolvulus arvensis (perennial broadleaf)

Elizabeth Lorenz is the Home and Real Estate Editor at the Palo Alto Weekly.


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