- Author: Elaine Lander
- Editor: Karey Windbiel-Rojas
While many of you are preparing for the 4th of July holiday, we at UC IPM are also thinking about stars and stripes but in a slightly different way: yellow starthistle and striped skunks.
As you celebrate July 4th, be sure to cover up to avoid mosquito bites when outdoors and watch out for yellowjackets that may be foraging for food while you barbecue. If you're watching fireworks light up the sky, we hope you'll be reminded of dandelion puffballs “exploding” and sending their seeds in the wind to establish new plants (and then look up how to remove them).
If you are going camping, be sure not to move any invasive insects with you by buying firewood near your camping location. At the campsite, beware of raccoons, ants, and poison oak!
Wishing you a safe (and pest free) holiday!
By Susanne von Rosenberg, UC Master Gardener of Napa County
It's May and everything is growing beautifully, including weeds. Even if your garden is exceptionally well-weeded, new invaders will creep in and demand attention. Our general reaction is to remove them as soon as we realize that we have them, and we think of a good, tidy garden as one that is free of weeds.
In general, until you are comfortable with weed identification, keeping your garden entirely free of things that you did not plant is a good approach. However, weeds can also provide some benefits, so learning about the different weeds can help you decide whether you just might let certain ones grow for a while. Over time, you may make friends with certain weeds and make them part of the cycle of your garden.
So what is a weed? Most commonly we consider something a weed if it is growing somewhere we don't want it to. Those California poppies you love in your flower beds just might be a weed if they start growing in your vegetable bed. I was surprised to learn that some people consider miner's lettuce, an edible California native that I carefully cultivated in my garden, a weed.
How can weeds actually be beneficial? Some weeds are edible, many can supplement your compost, and some help loosen the soil. They may provide erosion control and dust control. Some provide food or habitat for pollinators and other wild animals.
In addition, weeds can teach us about our soil. Certain weeds prefer specific soil conditions, so if you have those weeds, you can assume that your soil has those characteristics.
Common edible weeds include purslane, dandelion, lamb's quarters, nettles, fennel and chickweed. If you're not sure what you're looking at (you only know it's not something you planted), you can use the weed identification tutorials and information on the University of California Integrated Pest Management (UC IPM) site. If you're going to eat weeds (the ultimate revenge), use common sense. Never eat anything if you're not totally certain you've identified it correctly.
Many weeds make good additions to your compost or can serve as mulch. Annual weeds that have not developed flowers can be chopped up and left in place, although in winter and in moist areas of your garden, you have to make sure they don't re-root. You can also chop them and add them to your compost bin.
Those parts of perennial weeds that won't re-sprout can also be added to compost or used as mulch. With perennial weeds, though, it's important to know how they propagate so you don't inadvertently spread a problem. If a perennial weed has not flowered, you can also let it dry out completely (think completely crispy and brown) and then put it into your compost.
Some weeds improve soil by growing deep roots that break up the subsoil (the layer immediately below the topsoil). That allows the weaker roots of more delicate plants to access the water and nutrients there. Some common weeds with deep, strong roots include wild chicory, plantain, sow thistle and vetch, as well as lamb's quarter and purslane. Cut these weeds off at the soil surface before they start to flower. The roots will decay in place, adding organic matter to your soil. The tops can go into your compost. You'll get the most benefit if you keep these weeds fairly far apart; if they grow close together their roots won't penetrate as deeply.
Some weeds are great for attracting pollinators. However, you have to let the weeds flower. The mustard we see flowering in Napa Valley vineyards is one example. Fennel, wild radish and pigweed are other examples of weeds that are good pollinator plants. Pull them as soon as they have bloomed, and do not put the spent flowers in your compost.
Weeds can also act as living mulch. This feature can be particularly helpful in winter, if you are not growing vegetables or an intentional crop such as fava beans. Almost any annual weed can serve as living mulch. (You do not want to give perennial weeds the benefit of extra growing time.) Some annual weeds, such as chickweed and purslane, will form a mat as they grow and thus help suppress other weeds.
Finally, weeds give you clues about what is going on with your soil. Like other plants, weeds have specific soil preferences. Chicory, purslane and lamb's quarters are generally good news because they indicate rich soils. Thistles, wild turnip and bindweed, on the other hand, can indicate that you have compacted soil or a crusted soil surface. Poor drainage can be indicated by weeds such as sedges and Bermuda grass.
Research your weeds and learn what they tell you about your garden. Whether as indicators, food or soil improvers, weeds can be garden helpers, too.
Weed photo gallery list from UC IPM is here, a LIST OF ALL WEEDS. Find the common name to see a photo.
http://ipm.ucanr.edu/PMG/weeds_all.html
If you wish to ID the weed, use the UC IPM weed ID tool here:
http://ipm.ucanr.edu/PMG/weeds_intro.html
The UC Master Gardeners of Napa County are volunteers who provide University of California research-based information on home gardening. To find out more about home gardening or upcoming programs, visit the Master Gardener website (napamg.ucanr.edu). Our office is temporarily closed but we are answering questions remotely and by email. Send your gardening questions to mastergardeners@countyofnapa.org or leave a phone message at 707-253-4143 and a Master Gardener will respond shortly.
Dandelions are broadleaf plants easily recognizable by their bright yellow flower and puffball of white tufted seeds heads. While this plant is appreciated as a food or herb by many, for equal numbers of others it is regarded as a weed when found growing in lawns, ornamental plantings, and athletic fields throughout the year.
For helpful nonchemical and chemical management solutions to help you control this weed, read the newly revised Pest Notes: Dandelion by UC Cooperative Extension Advisor John Roncoroni.
- Author: Karey Windbiel-Rojas
We've had some rain in our area lately so you are probably seeing some weeds starting to grow in your garden or lawn. Among the few new weeds poking out in my landscape is dandelion, my husband's least favorite weed on Earth.
Hopefully you are aware of UC IPM's YouTube video series, but if not, we have a few dozen short videos cover pest topics such as catching a spider, trapping snails and slugs, and how to remove dandelions.
The "How to Remove Dandelions" talks about different nonchemical tools you can use to pull out unwanted weeds and discusses the importance of getting as much of that tap root as possible.
- Author: Cheryl A. Wilen
[From the UC Weed Science blog]
More and more, cities and public agencies are being asked to review and revise (and in some cases develop) their pesticide use policies. Often this change is requested by well-meaning members of the community after reading news articles and then becoming concerned about potential toxic effects of pesticides on children or the environment. In the case above, the grounds crew was also responding to requests from a public interest group that wanted them to reduce synthetic herbicide use and they were experimenting with natural and sustainable landscaping and organic weed control.
Integrated pest management (IPM) programs are just that – INTEGRATED. IPM programs combine or stack management approaches to balance the desired effect (e.g. higher crop yield, decreased plant damage, etc.) with cost of the desired goal and environmental impacts.
From What is IPM?:
The most effective, long-term way to manage pests is by using a combination of methods that work better together than separately. Approaches for managing pests are often grouped in the following categories.
Biological control
Biological control is the use of natural enemies—predators, parasites, pathogens, and competitors—to control pests and their damage. Invertebrates, plant pathogens, nematodes, weeds, and vertebrates have many natural enemies.
Cultural controls
Cultural controls are practices that reduce pest establishment, reproduction, dispersal, and survival. For example, changing irrigation practices can reduce pest problems, since too much water can increase root disease and weeds.
Mechanical and physical controls
Mechanical and physical controls kill a pest directly, block pests out, or make the environment unsuitable for it. Traps for rodents are examples of mechanical control. Physical controls include mulches for weed management, steam sterilization of the soil for disease management, or barriers such as screens to keep birds or insects out.
Chemical control
Chemical control is the use of pesticides. In IPM, pesticides are used only when needed and in combination with other approaches for more effective, long-term control. Pesticides are selected and applied in a way that minimizes their possible harm to people, nontarget organisms, and the environment. With IPM you'll use the most selective pesticide that will do the job and be the safest for other organisms and for air, soil, and water quality; use pesticides in bait stations rather than sprays; or spot-spray a few weeds instead of an entire area.
Another component to an IPM Program is the use of guidelines or thresholds to make a decision about when a management action is needed. This threshold must be realistic and in landscape and turf management is often set by the budget. So while a parent may want to see a beautiful weed-free lawn as they enter a school, a local decision about not using an herbicide would make it infeasible because the alternatives would require additional mowing, trimming, and hand weeding. This in turn, would require much more grounds staff time than what the budget would allow. Increasing the grounds budget is not helpful because that would take away funds from the core mission of the school.
So what to do? When the chemical component of an IPM program is no longer an option and weed management must rely on physical and mechanical methods something's got to give. And that thing is a change is attitude or expectations of what the site should look like. In the long run, that will become the new normal.
For information about managing weeds in lawns, consult the UC Guide to Healthy Lawns.