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.
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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[Ed note: Pictures of their favorite flowers and the associated butterflies are posted in the order listed by Penny Pawl.)
This has been a beautiful, bountiful year for butterflies in my garden. I have been hand-raising butterflies for many years now. It's my effort towards giving them a better chance at life.
Butterflies start in March when the flowers and vines begin to put out flowers and leaves. The Dutchman's pipevine (Aristolochia macrophylla ) puts out its little pipes in March. These blooms are pollinated by gnats. The leaves start to grow about the same time, and the Pipevine Swallowtailbutterflies are programmed to leave their pupae at this time. Most of them have been waiting almost a year to complete metamorphosis and are happy to be flying in the sun, gathering nectar from flowers and laying eggs.
When I see a female laying eggs, I search through the vine and usually find eight to ten little golden eggs in a cluster. Before a predator can get to them, I take the eggs in the house and put them in a small container. The container keeps them and the leaves from drying up. In less than a week, the tiny caterpillars are born. At that point, I know that I am committed for five weeks before they will make a pupa.
Once I commit to raising them, I clean their containers daily and make sure they have plenty of pipeline leaves, their preferred food. Occasionally I run out of leaves from my vine, but I know where another vine is and I will 'borrow' some of its leaves.
Monarch butterflies make their first flight through Napa Valley in April and May, heading north. To be ready for them, I grow a number of types of milkweed (Asclepias) that bloom at different times in spring and summer. The native milkweed (Asclepias speciosa) is usually growing when the Monarchs pass through. They may lay eggs if the plant has tender young leaves.
This past spring I gathered about 20 Monarch eggs. They are small, white and found on the underside of milkweed leaves. When I gather the eggs, I take a piece of leaf with me so when the eggs hatch they have some food. Right now the butterflies are ignoring Asclepias speciosa as the leaves are old. Instead they are laying their eggs on narrow-leaf milkweed (Asclepias fascicularis). I have lost count of the number of Monarchs I have raised in my house this year, but it must be around 50.
I was gone for a couple of weeks in June when another group of Monarchs came through the garden. Every milkweed variety that I grow had been munched. I found caterpillars of various sizes and took them inside to complete their growth. Monarchs take less than three weeks to mature and become a pupa. They will emerge from the pupa in another two weeks. Since they are hatching in my yard and I have plenty of flowers, they stay a while and lay more eggs.
Anise Swallowtail Butterflies feed on fennel (Foeniculum vulgare) and members of the parsley and carrot family. My fennel had struggled for years as gophers love it, too. I finally put the plant in a large pot to protect the roots and sunk the pot in the ground. The roots grow out the holes in the pot and the main plant is saved. This seems to work, and I have found tiny caterpillars on the fennel. So far this year, I have more than 20 that are either in pupae or eating fennel like there is no tomorrow.
All three of these members of the Swallowtail family taste bad to birds. However, that does not stop spiders, wasps and native bugs from dining on them. Lizards also like them. A few years ago, small parasitic flies laid eggs in one group of Anise Swallowtails I was raising. This killed the caterpillars when the eggs hatched.
These butterflies live only six to eight weeks. During that time they will lay 500 to 600 eggs. Not all the eggs are fertile; some are defective and the newborns die before they mature. But by hand-raising them, I am giving more butterflies a chance to have their flying days. In nature, only a small percentage make the transition.
When I started raising the Pipevine Swallowtail, I saw only a few, but now many visit my vine all summer long. Last year, in late September, two large Pipevine caterpillars were still feeding on the vine.
You don't have to hand-raise butterflies as I do, but you can help them survive by planting nectar plants. Grow native Pipevine, native milkweeds and other plants that butterflies need to lay eggs and feed. Never use pesticides; butterflies are not immune.
Gardening for Butterflies is an excellent resource. You'll also find a lot of good information on the life cycle of butterflies online.
Tree Walk: Join U. C. Master Gardeners of Napa County for a free guided tree walk through Fuller Park in Napa on Monday, September 12, from 10 a.m. to 11:30 a.m. Registration is recommended as space is limited. Meet at Fuller Park, corner of Jefferson and Oak Streets. Online registration or call 707-253-4221. Trees to Know in Napa Valley will be available for $15. Cash or check payable to UC Regents. Sorry, we are unable to process credit cards.
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.