- Author: Richard Smith
- Posted by: Gale Perez
Weed control in lettuce and other crops is a key issue this time of year. Purslane is particularly problematic and is adapted to warm conditions and can grow very rapidly especially during July and August. At times growers and PCAs are disappointed with the efficacy of Kerb on this weed. Kerb is effective in controlling purslane but it is readily leached and, if applied at planting, it can be moved below the zone of germinating weed seeds with the germination water. For instance, 6-8 hours of sprinkler water (1.5 to 2.0 inches) are commonly applied in the first germination water which can move the Kerb below the upper 0.5 inch of soil which is the zone where the weed seeds germinate; the movement of Kerb with the germination water is particularly problematic on sandy soils. Prefar does not leach and thus provides most of the purslane control when the two materials are tank mixed (Figure 1). However, Prefar does not control shepherd's purse or nightshades which can also be problematic in lettuce fields. Therefore, it would be advantageous to optimize the efficacy of Kerb to maximize the control of purslane as well as other weeds.
In the desert, the use of delayed applications of Kerb has been used for many years. Due to the large amounts of water that are applied in their hot conditions, Kerb is applied in the 2nd or 3rd germination water, approximately 3-5 days following the first germination water, just prior to the emergence of the lettuce seedlings. This technique can also be utilized in the Salinas Valley. We have looked at this technique over the years and have found it to improve the efficacy of Kerb (Figure 2). These data illustrate the loss of control of purslane by Kerb when applied before the 1st germination water, as well as the improvement in efficacy that results when applied following the 1st germination water. It also illustrates the role that Prefar plays in the control of purslane when the efficacy of Kerb is lost by leaching. It should be mentioned that the label states that the maximum amount of Kerb that can be applied through the sprinklers is 2.5 pints/A and the amount used in this trial was for experimental purposes only. Clearly there is benefit from applying the Kerb later in the 2nd or 3rd germination water, however, we observed that applying the Kerb at the end of the 1st germination water also provided improved efficacy of Kerb. Clearly, anything that helps to keep the Kerb in the top 0.5 inch of soil improves its efficacy.
Here are some details that need to be considered regarding the application of Kerb later in the germination phase of the crop: There is a need to use an injection pump and tank. We have typically used a tank with a circulating mechanism to keep the Kerb in suspension while the injection was occurring. The material needs to be injected into the mainline in a location where proper mixing can occur before it begins to flow down the laterals. The most difficult issue that growers face is the compatibility of the injection with surrounding crops. This is probably the greatest challenge and must be carefully thought through before attempting an application.
Another idea that we explored last year was the use of an additive to help retain the Kerb in the upper portion of the soil where it can be most active. However, we did not see improved efficacy in two 2018 trials (data not shown).
Many growers now are now using drip irrigation to germinate lettuce. Grower may apply the same amount of water with drip germination as with sprinklers, but the movement of the water is different which affects a surface applied material differently. With this method of germination, there are a couple of interesting dynamics that occur: 1) Kerb is not pushed too deep by this germination method and effectively reduces weed populations whether injected into the germ water (currently not a registered method of application) or sprayed on the soil surface and activated by the drip germination water (Table 1); and 2) fewer weeds emerge with drip germination than with sprinklers, regardless of the herbicide program.
By T. Eric Nightingale, UC Master Gardener of Napa County
I love California native plants. I also love to eat. Until recently I had not considered the possibility of an overlap between these two passions. Eventually it occurred to me that there must be many edible native plants to complement those brought here by European settlers.
Would it be possible to plant a garden of perennial natives that also supplies food? I found the idea appealing, in part because I figured such a garden would produce food easily. Our state's native plants tend to need less care, often less water and can be less prone to attack by insects and disease. I realized that that my fantasy of walking through my self-sustaining Californian Eden, picking fruit to eat as I wander, was probably not achievable, but still I set out to investigate the possibilities.
Indeed, many native plants are edible, but you must proceed with caution. Some are safe to consume just as they are, but many require some form of preparation to make them safe, or even desirable, to eat. Before eating anything unfamiliar or anything you have foraged in the wild, do your research and be sure you are not taking a risk.
That said, I have found many exciting edibles around our state, many that have been right under my nose for a long time. Most fascinating to me were the edible cacti and succulents. The fruit of the prickly pear cactus (Opuntia spp.) is well known. New to me, however, was the chaparral yucca (Hesperoyucca whipplei), the flowers and seeds of which can be eaten either cooked or raw.
The barrel cactus (Echinocactus acanthodes) grows a crown of attractive flowers that leave behind small, edible (but not very tasty) fruits that resemble miniature pineapples. More appealing is purslane (Portulaca oleracea). Often considered a weed, this tender succulent is flavorful and a great addition to salads.
Sedum spp., also called stonecrop, is used as a ground cover in drought-tolerant landscaping. All species are technically edible but can cause gastrointestinal distress if consumed in high quantities. They apparently have a peppery flavor that may justify their addition in a creative meal.
The leaves and flowers of the ice plant (Carpobrotus edulis) are reportedly edible raw. You will recognize the pointed leaves and brightly-colored flowers of this vine-like succulent at almost any stop along the California coast. As this plant is not native, and is in fact extremely invasive, you may be doing a public service by consuming it. Perhaps if we all made a habit of eating ice plant salad, we might help clear the way for native plants to reclaim their lands.
Many native shrubs produce edible berries. My favorites are currants and gooseberries (Ribes). The berries are tasty and can be made into jam, but these shrubs sit at the top of my list for their flowers. The colors and shapes are impressive, guaranteeing aesthetic as well as culinary appeal. The berries of the black hawthorn (Crataegus douglasii) shrub are delicious and useful in pies and preserves. The foliage and flowers, while not particularly striking, are attractive and a fine addition to any landscape.
Berries in the wild are often misidentified, so I recommend sticking with home cultivation. Birds like them, too. While growing currants and gooseberries is an excellent way to support local wildlife, it can be frustrating if you dream of a pantry full of gooseberry jam.
One group of often-overlooked edibles is what I dub “roadside salad.” Most of the members of this little club may be recognizable to many people as weeds. One such roadside trooper is miners lettuce (Claytonia perfoliata). Its disc-shaped leaves are tender and have a delicate flavor. To add some zing to your roadside salad, look for the peppery bittercress (Cardamine spp). This plant has a much more traditional weed-like appearance.
Surprising to me, native cattail (Typha domingensis) is also edible. The young shoots can be eaten raw and are said to taste like corn. The seeds and starchy roots can also be used if cooked.
One definition of a weed is a plant growing in the wrong place. If we appreciated these plants a bit more, we might start to view them not as weeds but as convenient snacks.
Workshop: U. C. Master Gardeners of Napa County will conduct a workshop on “Rose Care” on Saturday, June 2, from 10 a.m. to noon, at University of California Cooperative Extension, 1710 Soscol Avenue, Napa. Roses will grow without any care. But they will thrive with a little TLC. UC Master Gardener rose experts will answer your questions regarding rose care at this popular forum. By June, the first spring blooms have faded, and many plants are beginning to show evidence of stress. Look for black spot, rust, mildew and possible aphid infestation. Bring samples for identification. Online registration (credit card only); Mail-in/Walk-in registration (check only or drop off cash payment).
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.
- Author: Ben Faber
Rain is unusual in that it germinates weed seeds and then the need to manage them in some fashion arises. Many subtropical tree growers do not like the potential impact of pre-emergent herbicides on tree growth due to potential damage to shallow roots. Lemon growers rely fairly heavily on the post-emergent glyphosate, especially since there are cheap generic versions available. I don't know of many avocado growers who use a pre-emergent, using the natural mulching effects of fallen leaves, introduced mulch, the natural shading of the canopies and glyphosate.
I am not aware of any field studies that have shown that pre-emergents can cause root damage or reduction of tree growth or yield. There are a number of registered chemicals with different modes of action, so one would expect to see more use as practiced in other tree crops, but there is a reluctance that is based on some possible damage to trees. So, a lot of glyphosate is used and to some extent another material, glufosinate, is also used in citrus.
One of the issues that has arisen with glyphosate use has been the resistance of some weed species to this material. There are some thirty-seven species of resistant weeds in the world. In California orchards, the biggies are Hairy Fleabane, Horseweed and Johnson grass. Resistance means that you can spray the plants, even in their small stages and there's little or no effect. A non-resistant species would just wither, turn yellow and die down to the roots.
There are always plants like horsetail or purslane which have a surface that does not absorb material very well. They appear to be resistant, but aren't. Once you use the maximum dose, with a spreader-sticker or another adjuvant, the herbicide gets into the plant and it dies. Also, the key is timing, young plants being much more susceptible than bigger plants with a less absorptive surface.
This year, though with all the rains, there've been calls about not just horseweed being tough to get, but also nutsedge. Nutsedge, as far as I know, has no documented resistance, but it does have a waxy surface that gets thicker with the age of the plant. With all the weeds, people have gotten behind and the weeds have gotten out of hand and the older plants are harder to spray out. It takes more tact to get at them when they get older.
Nutsedge also reproduces from swollen underground stems called tubers or “nuts”. They aren't nuts – seeds – and some people mistake them for a grass, which they are not. They are a sedge. They reproduce primarily through the “nut” and they form lots of “nutlettes”, each of which can form a new plant. If you pull the plant up and don't get all those nutlettes, you are actually increasing the number of plants that will form. It is tricky to deal with and a good thorough spraying can control them, if done at the right stage.
It turns out that these nuts are eaten by lots of animals – pigs, chickens, humans. In the South, pigs and chickens have been used to clear fields of nutsedge before planting rice. The presents of nutsedge around the world is quite likely due to humans having spread it around the world as a food. A poor person's nut.
So, this brings me to the title of this article. Why not grow it for sale? Intercrop it with lemon. Drip irrigate the nutsedge separate from the trees and figure out the pesticide schedule and other management issues and there's a new crop for sale. Foraging for malva, nettle, mustard, pursalane, dandelions and other unconventional edible plants has become a big deal in urban agriculture. You see “wild plants” for sale in the farmers markets. Euell Gibbons has become not just fashionable but commercial. Kale has taken the country by storm. Who would have thought it?
Root System of Yellow Nutsedge
![nutsedge nuts nutsedge nuts](/blogs/blogcore/blogfiles/44614.jpg)
By Pat Hitchcock, U. C. Master Gardener of Napa County
This winter seems to be a promising one; it's raining regularly. But along with the filling reservoirs and green hills come a multitude of weeds.
University of California Agriculture and Natural Resources publishes “Weed Pest Identification and Monitoring Cards” (Publication 3541) that identify nearly 50 different broadleaf and grassy weeds common in California. The cards have pictures of the plants at different stages of growth, as well as information on how they spread, where they grow and how to control them. Alas, most of them grow well on my property.
Weeds can't grow without water. Once the rains begin, they sprout from seeds or emerge from their dry-season dormancy. I was curious as to where they originated and why so many thrive here, so I began researching. It is daunting to discover that the weeds in my backyard come from all over the world.
Take dandelions (Taraxacum officinale). There are native American versions, but the more widespread dandelion was imported from Europe as an edible and medicinal plant. Today, most of us consider it a weed, although some people still enjoy it as a cooked green or salad.
Another common edible weed is purslane (Portulaca oleracea), a succulent summer annual with small yellow flowers. Purslane has been eaten throughout Europe, Asia and the Middle East since prehistoric times, but when it arrived in the New World is unclear. It makes a lemony addition to salads.
Several annual grasses thrive in Napa Valley winters, including Italian ryegrass (Lolum multiflorum), wild oat (Avena fatua) and ripgut brome (Bromus diandrus). These appear to have originated in the temperate regions of Europe but are widespread in our grasslands, parks and farmland. Besides taking over cultivated soil and crowding out garden plants, some have troublesome seeds that catch on pet fur or clothing and work their way into flesh. Pet owners know what misery these so-called “foxtails” can cause dogs and cats.
One of the most persistent weeds in my garden is field bindweed (Convolvulus arvensis). This perennial plant originated in Europe and Asia and most likely arrived with crop seeds in the 1700s. It quickly became invasive. Roots can grow as deep as 10 feet and prefer moist, fertile soil. That pretty much describes my vegetable beds; no wonder I am constantly pulling and digging this plant out.
Redstem fillaree (Erodium cicutarium) is a plant I loved as a child. I liked to pick off the drying seed head and watch it coil when separated from its flower. Now, as a gardener, I find its ability to stick to clothing, especially socks, truly annoying. Native to the Mediterranean basin, this plant is edible, but the leaves are best eaten young.
Mustard (Sinapsis arvensis) is another weed originating in the Mediterranean basin. Legend has it that the Spanish padres deliberately sowed mustard along El Camino Real to mark the way. More likely, this plant arrived in North America accidentally like so many others.
Wild radish (Raphanus raphanistrum) is related to mustard.Native to Asia, it has spread all over the world. According to the weed I.D. cards, it is similar to Raphanus sativus, the common radish, and hybridizes easily with it. Both have four-petal flowers that may be white, yellow or pale purplish-pink. They bloom in early spring and continue as late as July, producing a lot of seeds over several months. Seeds can remain viable in the soil for 30 years, so preventing seed production is one key to controlling the weed.
Redroot pigweed (Amaranthus retroflexus) is another apparently edible weed in our region. It is native to the tropical Americas but has naturalized all over the world. An annual plant, it spreads by seed that can live up to 40 years.
Prickly lettuce (Lactuca serriola) is an unattractive plant with prickly leaves and stems and bitter sap. Who would guess that it is the nearest wild relative of our common garden lettuces? It appears to have originated in Europe, Asia and North Africa, and ancient Greeks and Egyptians used it.
Some say that a weed is any plant in the wrong place. The weeds I researched thrive all over the world due to their ability to out-compete other plants for water, sunlight and nutrients. Controlling weeds is important both in cultivated gardens like my vegetable patch and in natural areas where they can crowd out native plants.
As the I.D. cards suggest, the best way to control most weeds is by manually removing them before they can bloom and produce seed. Another word for that is weeding. Winter is a good time to get out there and enjoy, I mean control, your weeds.
Workshop: U. C. Master Gardeners of Napa County will hold a workshop on “Fruit Tree Pruning and Grafting” on Saturday, January 21, from 9 a.m. to 2 p.m., at the University of California Cooperative Extension office, 1710 Soscol Avenue, Napa. The dormant season is the best time to prune your deciduous fruit trees to increase vigor. Join the Master Gardeners fruit-tree team for this workshop showing techniques to develop healthy and productive fruit trees. A local expert grafter will give a grafting demonstration. The afternoon field trip offers home gardeners the opportunity for a hands-on experience. Dress for seasonal outdoor weather and bring your pruners. Online registration (credit card only); Mail-in registration (check only or drop off cash payment)
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.
A list of useful weeds comes quickly to mind. Think of dandelions, whose first tender spring greens are delicious in salads or steamed. Later, the cheerful dandelion flowers can be steeped, sweetened and fermented into a mellow wine. That tasty wine is one good reason to harvest the blossoms before they turn into the fluffy puffs that children blow to make wishes come true.
In some gardens, artichoke thistles, cardoon stalks and spring greens such as chickweed and miner's lettuce are considered invasive, but they are welcome volunteers in my garden. The lacy yellow fennel blossoms that adorn Napa Valley roadways and meadows provide pollen to rub on chicken or fish if you are patient enough to collect it. Wild fennel seeds can be chewed, used to flavor biscotti, or crushed and toasted to add to olives and olive oil.
All these plants are weeds when they grow where we don't want them, yet all are considered a culinary treat by people in other parts of the world.
One weed that is prolific in many gardens is common purslane (Portulacaoleracea). It's easy to uproot, and yanking them up is preferable to hoeing or tilling since each little jade finger that breaks off can generate a sprawling new succulent.
Purslane is native to India and Persia and has fleshy stems and small yellow flowers. It was said to be one of Gandhi's favorite foods. The stems lie flat on the ground as they radiate from a single taproot, sometimes forming large mats of leaves. Purslane resembles a small-leaved jade plant. It is closely related to rose moss (Portulaca grandiflora), although grandiflora is a native of South Africa and treasured more for its flowers than its culinary attributes.
According to a University of Illinois web site, viable purslane seed has been found after 40 years. As the site says, you may find that depressing, or exciting.
If you want to eradicate purslane in your garden, do not let it go to seed. Flowers and seeds develop just three weeks after seedlings appear, so be vigilant. And even if you uproot the purslane, your work is not done. Be sure to discard the plants, because pieces simply lying on garden soil can root and take off again. For more information about purslane, go to http://www.turf.uiuc.edu/weed_web/index.htm.
You can sometimes find purslane at farmers markets, or you may find it in your box if you receive a produce delivery from a local farm. It contains a potent package of nutrients. Whether enjoyed raw in salads or cooked in soups and stews, purslane is rich in minerals, including calcium, magnesium, potassium and iron. It is also high in antioxidants, with more heart-healthy omega-3 fatty acids than any other plant.
For adventurous eaters willing to welcome a basket of weeds into the kitchen, purslane provides a lot of inspiration. The web site Epicurious (www.epicurious.com) has 23 recipes for purslane, including a purslane and parsley salad with cherry tomatoes, lemon and olive oil. A slightly more complicated recipe from the site is purslane and avocado tacos with salsa. (Mexicans know purslane as verdolagas.) Or how about a purslane, Meyer lemon and pear salad with kaffir lime vinaigrette?
Cooking purslane mellows its slightly lemony tang and wilts it like spinach so you will need a lot or it for cooked dishes. That tang and sturdy texture are wonderful in salads, pickles and fresh and cooked salsas.
Still not sure what to do with purslane? The most extensive list of ideas I have found is “45 Things to Do with Purslane” (http://chocolateandzucchini.com/ingredients-fine-foods/45-things-to-do-with-purslane). If you decide you want to grow purslane, you can find seeds at http://www.territorialseed.com/category/s?keyword=purslane. But first put on your shoes and go see if you are lucky enough to already have some growing in your garden. Then you won't have to buy it.
Workshop: Napa County Master Gardeners will conduct a workshop on “Cool Season Veggies” on Sunday, August 17, from 2 p.m. to 4 p.m., at the Yountville Community Center, 6516 Washington Street, Yountville.To register for the Yountville workshop call the Parks & Recreation Department at 707-944-8712 or visit their web site.The workshop repeats onSaturday, August 23, at U.C. Cooperative Extension, 1710 Soscol, Napa. Grow your own vegetables even when days are short and nights are cold. Learn which vegetables thrive in cooler temperatures, how to protect them from heat when they are getting started, and how to time planting to ensure months of harvest. To register for the Napa workshop: Online registration (credit card only) Mail in registration (cash or check only).
Master Gardeners are volunteers who help the University of California reach the gardening public with home gardening information. Napa County Master Gardeners ( http://ucanr.org/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.
Napa County Master Gardeners welcome the public to visit their demonstration garden at Connolly Ranch on Thursdays, from 10:00 a.m. until noon, except the last Thursday of the month. Connolly Ranch is at 3141 Browns Valley Road at Thompson Avenue in Napa. Enter on Thompson Avenue.