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.
- Author: Kathy Keatley Garvey
And she's beautiful!
It all began with finding two anise swallowtail chrysalids clinging last July to the fennel stems in our pollinator garden in Vacaville, Calif.
To protect them from predators and the elements, we tucked them inside a zippered net butterfly habitat and placed “the prized package” in the corner of a laundry room to await the spring of 2018--and eclosure.
The first day of spring, March 20, came and went. Then 288 days slipped by. The chrysalids remained intact. Were they viable?
We showed images of the chrysalids to butterfly guru Art Shapiro, distinguished professor of evolution and ecology at the University of California, Davis, who's been researching the butterfly population of central California for more than four decades.
“They both look OK—the intersegmental membranes are not showing,” he said. “Stick them in the refrigerator for a month and try again. If they are a coast range population, some may diapause up to 5 years. If a valley population, multiyear diapause is very unusual.”
Shapiro advised that we “put them in a lidded container” to prevent their drying out. “Diapausing pupae only breathe once or twice a day.”
So, on June 5, in the refrigerator they went, joining assorted cups of yogurt, bags of fruits and vegetables, jars of peanut butter, cartons of fat-free milk and what-have-you.
What a life!
Then on July 4, Independence Day (but with no fanfare, ceremony or celebration) out they came. (The yogurt, fruits and vegetables, peanut butter, milk and what-have-you stayed behind.)
We placed the (probably) thoroughly confused chrysalids back in the butterfly habitat, but this time, outdoors, and right next to their host plant, fennel. Daytime temperatures climbed to 100 degrees and night temperatures dropped into the 50s.
Nothing happened. Nothing.
Just as we were wondering if they were still viable, we saw a winged burst of yellow, black and blue on Sunday night, July 14. A long-awaited eclosure!
It's a girl! (as identified by Professor Shapiro). (Read more about the anise swallowtail, Papilio zelicaon, on his website.)
Early Monday morning, we dipped a fennel blossom into a mixture of 10 parts water and one part honey. Food! She drank heartily. Then we placed her atop the towering fennel so she could warm her flight muscles.
Two hours later, Ms. Anise Swallowtail became part of the Wonderful World of Butterflies. She circled the house, returned to nectar on the Mexican sunflower (Tithonia), and left. No fanfare, no ceremony, no celebration. This is her world now.
The other chrysalis? It remains intact. Fingers crossed that it, too, will survive.
It doesn't get much better than this--in a world where kindness matters. It always has.
- Author: Kathy Keatley Garvey
It's a bird! It's a plane! Is it Superman?
No, it's a bird dropping.
If you're growing sweet fennel (anise), you may have noticed what appear to be two species of swallowtail butterflies populating your plant.
You'll see larvae (caterpillars) that are pale green with black bands containing orange spots. But look more closely and you'll see the smaller larvae or early instars. They look like bird droppings. A gift from above?
Those are both the immature stages of the anise swallowtail, Papillo zelicaon, (Check out the beautiful images of the butterfly and its immature stages on the Natural History of Orange County website.)
Butterfly guru Art Shapiro, UC Davis distinguished professor of evolution and ecology, says the anise swallowtails have several generations (late February or March-October) "and breed very largely on sweet fennel (anise), Foeniculum vulgare and in the first half of the season, poison Hemlock (Conium maculatum)."
These are naturalized European weeds, he says on his website. "We believe this ecotype originally lived in the tule marshes and bred on water hemlock (Cicuta) and another Apiaceous plant named Oenanthe. These are still used but only rarely in comparison ot he weeds; they are the only native hosts available in the Mediterranean summer that could have sustained repeated breeding."
Colors of the iconic anise swallowtail caterpillars also differ. "In hot, dry sites there is more green and less black, while under cool, humid conditions, the green may even disappear!" Shapiro says. And the pupae (chrysalids) may be brown or green.
Meanwhile, our caterpillars are feasting on the fennel and shedding their protective, camouflaged "bird dropping" skin. The California scrubjays that dine on the Gulf Fritillary caterpillars on the nearby passionflower vine (Passilfora) don't seem to notice.
Here's hoping they won't touch the anise swallowtails. Why would they want to eat something that looks like bird poo?
- Author: Tunyalee Martin
Summer—it's a time for swimming, BBQs, camping, and eating invasive species
Last week during California Invasive Species Action Week (June 2 – June 10), we highlighted several pests, but there are many more invasive species out there. Now that you know about them, share your knowledge of invasive species with others. And no matter what your summer plans, here are some things YOU can do about invasive species from the California Department of Fish and Wildlife and California Department of Food and Agriculture.
YOU: I'M TRAVELLING TO AMAZING PLACES
- Learn what plants and animals you could bring into California.
- Don't pack a pest! Declare all food and agricultural items from other states or countries.
- Find out which species are threats to California.
- Learn about California's invasive plants.
- Avoid spreading forest pests: buy your firewood where you burn it.
YOU: I'LL BE WORKING IN MY GARDEN
- Remove invasive plants from your property.
- Select native or non-invasive plants for your garden.
- Use only certified weed-free forage, hay, seed, mulch, soil, and gravel.
- Learn alternatives to releasing unwanted fish, aquatic plants, and other pets.
- Monitor plants and trees for symptoms of infestations and disease.
- Learn about California's invasive plants.
- Have you spotted an invasive species? Tell us where by reporting your sighting.
YOU: I'LL BE NEAR THE WATER OR ON A BOAT
- Join the statewide citizen science effort to monitor for quagga mussels.
- Join the iNaturalist project, California Nerodia Watch, and help us find Nerodia watersnakes.
- Make sure to Clean, Drain, and Dry (PDF) your boat after each outing.
- Learn alternatives to releasing unwanted fish, aquatic plants, and other pets.
- Visit your favorite local, state, or national park, ecological reserve, recreational area, or nature center and ask about their volunteer programs.
- Learn about California's invasive plants.
- Have you spotted an invasive species? Tell us where by reporting your sighting.
YOU: I'LL BE OUT AND ABOUT CAMPING, HIKING, OR RIDING HORSES
- Use only certified weed-free forage, hay, seed, mulch, soil, and gravel.
- Avoid spreading forest pests: buy your firewood where you burn it.
- Prevent the spread of plant pathogens that damage and kill California's native plants and trees.
- Learn about California's invasive plants.
- Visit your favorite local, state, or national park, ecological reserve, recreational area, or nature center and ask about their volunteer programs.
- Have you spotted an invasive species? Tell us where by reporting your sighting.
YOU: I'LL DEFINITELY CONTINUE TO LEARN ABOUT INVASIVES
- Get to know your local invaders.
- Learn about California's invasive plants.
- Find out which species are threats to California.
- Learn alternatives to releasing unwanted fish, aquatic plants, and other pets.
- Eat them. Yum. Check out these websites to find out who is edible and how to prepare them.
- Invasive-eats.com (California-specific)
- Invasivore.org (under construction but hopefully back soon)
- EatTheWeeds.com
- EatTheInvaders.org
If you missed it this year, help in the fight next year by learning and participating during California Invasive Species Action Week.
Somehow we missed this in July. We posted the article on our Facebook page. Have you visited AND LIKED us at UC Master Gardeners of Napa Valley? Please do!
We missed posting this to our blog. Penny Pawl, our extraordinary butterfly caretaker, explains how planting fennel led to so much else in her garden! You will notice a change in the font size partway through the article. The original does not have this change. I have tried to change it on this page, and have resized the original twice, to no avail. It posts those paragraphs in enormous font size. Think that's why it was skipped--because I couldn't fix the font.
Fennel is a Mediterranean plant that has been introduced to the United States. Over many years, it has naturalized in our area. Recently I saw an anise swallowtail butterfly visiting my fennel (Foeniculum vulgare) so I went out and looked for eggs and babies. The babies look like bird droppings as they are black with a white strip through their middle. In this search and subsequent ones, I discovered many small bugs living in the fine leaves of the fennel.
I originally planted this fennel to attract butterflies. The anise swallowtail is a beautiful yellow and black butterfly that especially likes the nectar of lily-of-the-Nile (Agapanthus). A few years ago, I was raising four anise swallowtail larvae and suddenly all but one died. I continued to watch the survivor until, one day, a small larva hatched out of his side. Then the caterpillar died.
I decided to observe what the larva turned into when it hatched. It was a small parasitic fly, and it had laid the egg before I had collected the caterpillars.
Butterflies of all species have a rough time laying eggs and raising them to full-size adults. That's why I take the time every summer to raise as many larvae as I can in my house. As soon as they pupate, or hatch, I let them pump up their wings and leave.
As I worked my way around the fennel, I found two tiny black-and-white spiders. Each one had created a web, and as soon as the spider caught an insect, the insect was carefully wrapped in the web and stored for the future. Both of these guys stayed close to their catch to guard it. They left only to gather more insects.
The one bug that puzzled me was an almost-yellow stink bug. Although I am always watching bugs, this one was completely new to me. over several days, I observed him. He moved to my milkweed plants, which concerned me, so I captured him in a jar.
I was finally able to identify the bug as a redshouldered stink bug (Thyanta pallidovirens). It is considered a good bug compared to many stink bugs and the invasive brown marmorated stink bug (Halyomorpha halys). Most stink bugs feed on and damages plants while the redshouldered stink bug eats other insects. All stink bugs have a straw-like mouth, the brown marmorated stink bug and plant feeding stink bugs carries theirs down their stomach and the redshouldered stink bug has his pointed forward. I did observe him sucking on a dead bug but a live insects would be his preference.
As my fennel is finally preparing to bloom there are many small flies and wasps visiting the buds. The swallowtail caterpillars are growing. In fact one has already left the pupa and is hopefully laying more eggs.
To raise the caterpillars in the house, I collect the eggs or very small caterpillars and put the them into small containers. When the eggs hatch the caterpillars are about 1/8 inch long. I add more fennel daily and clean ou their droppings. After shedding and eating their skin four times, they change from black and white to green with yellow and black markings. By this time they have tripled their size. (This size increase is common to all butterflies in the swallowtail family.) This amazing growth rate is the reason they shed their skin. After turning color, they eat without stopping. I have to transfer them to a larger container and I feed and clean their droppings twice a day. All they leave is fennel stems stubs.
Before the form a pupa, they go on a walk around the container. Once they settle down, it is a few hours before the skin covering opens for the last time revealing a pupa. This will be their home for weeks or even months. Most will spend the winter or "overwinter" in the pupa and emerge in the following spring to begin the process over again.
Master Gardeners are volunteers who help the University of California reach the gardening public with home gardening information. U. C. Master Gardeners of Napa County ( http://ucanr.edu/ucmgnapa/) are available to answer gardening questions in person or by phone, Monday, Wednesday and Friday, 9 a.m. to Noon, at the U. C. Cooperative Extension office, 1710 Soscol Avenue, Suite 4, Napa, 707-253-4143, or from outside City of Napa toll-free at 877-279-3065. Or e-mail your garden questions by following the guidelines on our web site. Click on Napa, then on Have Garden Questions? Find us on Facebook under UC Master Gardeners of Napa County.
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