By Susanne von Rosenberg, UC Master Gardener of Napa County
One of the reasons I really enjoy having fruit trees is that they are perennials: they give back a lot for relatively little effort. You can get the same benefits from perennial vegetables.
The most common perennial vegetables for our area are artichokes, asparagus and bunching onions (scallions). Others that are highly suited to our Napa Valley climate are cardoon (a relative of artichokes), tree collards (also known as tree kale or walking stick kale), walking onions (also called Egyptian onions) and nopales (prickly pear cactus pads). Additional options include sunchokes (Jerusalem artichokes), perennial arugula (caution: it self-seeds readily) and miner's lettuce (claytonia). In our climate, miner's lettuce acts like a self-seeding annual, but it is a perennial in areas where it receives sufficient moisture.
In addition, you can “perennialize” regular kale, garlic (for green garlic) and, to some degree, Swiss chard and broccoli. To start treating regular kale as a perennial, simply cut it back to a few inches of stalk when it starts to look tired and it will resprout. You can do the same with broccoli. You won't get another large head, but you will refresh the plant and get more small side shoots.
In my yard, Swiss chard readily self-seeds, so there is always some chard growing wherever I water regularly. If it's not in the way, I let it grow. If you plant garlic and don't harvest the bulb, it will sprout as a cluster of green garlic the following growing season and continue to create bulbs underground. Eventually, as with flower bulbs, you will have to dig it up and divide it. Keep some of the best bulbs and replant some cloves for more green garlic.
Think about the pros and cons when you consider adding perennial vegetables to your garden. The main advantage is that you only plant once, yet you harvest for multiple years. Because the plants stay in place longer, they develop stronger and more extensive root systems. This helps the plants take better advantage of available water and nutrients.
Because you're not replanting every year, you're protecting the soil ecosystem. For busy people, adding one or two perennial vegetables per year can be a way of building a productive vegetable garden without investing a lot of time.
You can also let the plants flower, which supports pollinator insects. Some perennials add beauty to your garden. Sunchokes, which are part of the sunflower family, will grow 8 to 10 feet tall with adequate water and produce numerous small sunflower-like flowers.
However, there are some downsides. First of all, you lose flexibility. You have to carefully consider how big the plants will get and whether they make sense at full size in their proposed location. Good locations for perennial vegetables include areas adjacent to other perennials (including berries, fruit trees and ornamental plantings), at the ends of annual vegetable beds and in groupings with other perennials that have similar water needs.
For many perennial vegetables, it takes longer to get harvestable produce. Also, you may need to keep watering them when the weather is dry. When we have a light rainy season, you'll likely have to keep irrigating.
If you are not rotating vegetables and you are keeping them alive year-round, you may have more pest problems. Control pests as soon as you notice them. If you have gophers, you may find that certain perennial plants, such as artichokes, need to be planted in cages because the roots are just too tasty for gophers to resist.
Finally, because you are continuing to water, you are also likely to continue to get weeds, so you will need to cultivate around the plants or mulch regularly to keep the weeds down. Also make sure to check that you are selecting the right kinds of perennial vegetables for your garden. Many common perennial vegetables, such as watercress, require relatively high amounts of water or need sandy, well-drained soil. Others can become invasive. Do your research or contact the Master Gardener help desk for more information.
There are many other perennial vegetables to try if you're adventurous. On the border between herbs and vegetables are sorrel and lovage, which can be used as salad greens, in soups and as seasonings. Daylily tubers, young shoots, buds and flowers are all edible. The leaves of scorzonera (black salsify) can be harvested and eaten just like lettuce. (If you harvest the edible roots, however, you will kill the plant.) Sweet potato leaves are also edible, as are linden tree leaves. Have fun diversifying your garden!
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Garden Advice from the Help Desk of the
UC Master Gardener Program of Contra Costa
(minor correction October 31, 2016)
Client's Request: How can I get rid of oxalis in my yard? I pull it out and think I've got it all, but it just comes back with more gusto the following year. It's annoying, to say the least!
Homeowners and gardeners wishing to eradicate Bermuda buttercup face a tenacious, prolific weed which has devised many successful survival strategies. Each year, after the first seasonal rains, and sometimes before in a dry year, about a dozen ovoid bulbils develop along the length of the threadlike, underground rhizome. These readily detach from the rhizome to replenish the soil seed bank.
Another survival technique of Bermuda buttercup is that, after initial removal by hand, new plants will grow from broken off stem segments left in the soil. Several passes at hand weeding may be necessary to completely remove this new growth. Discouraging survival of Bermuda buttercup can usually be accomplished by gently pulling on the plant and removing all of it just as it is about to flower. By this time, the parent bulb energy reserves are exhausted. The parent bulb should be completely dried out and most young bulbils are too immature to survive disturbance.
Though prevention is the best control method, soil solarization can reduce the bulb population. To be effective, solarization using a clear plastic tarp treated with an ultraviolet light inhibitor must be in place for no less than 4 consecutive weeks during June, July, or August. The sun's rays will heat up the soil to temperatures that are lethal to Bermuda buttercup bulbs (and most everything else in the top several inches). Some researchers investigating approaches for controlling Bermuda buttercup also suggest covering it with stiff cardboard and applying a thick layer of mulch. The goal is to weaken the bulbs and deprive the plant of sunlight, causing an inability to photosynthesize and eventual death by starvation. Chemical control can affect the top growth but is ineffective in preventing bulb germination.
The lack of movement of water and air between compacted clay soil molecules promotes the survival of Bermuda buttercup bulbils. Adding nitrogenrich organic matter will loosen existing soil particles and benefit soil structure by increasing porosity and improving drainage.
While complete eradication is practically impossible to achieve, following strict noncontamination practices, mulching, solarizing, improving soil structure and drainage are all steps gardeners can take to create an environment unfavorable to the establishment and survival of Bermuda buttercup.
For further information on managing this pest, visit www.ipm.ucdavis.edu and download UC's free Pest Notes publication 7444 entitled “Creeping Woodsorrel and Bermuda Buttercup.” (http://www.ipm.ucdavis.edu/PMG/PESTNOTES/pn7444.html)
UC Master Gardener Program of Contra Costa's Help Desk (CG)
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This is an updated article authored by Chantal Guillemin, UC Master Gardener, and originally published in the March 19, 2011, Contra Costa Times. The HOrT COCO blog editor takes all responsibility for the above updated version.
A minor error was corrected Oct 31, 2016 to reflect, per the Pest Note above that woodsorrel can be a pest in nursery container-grown plants, while Bermuda buttercup isn't. See the Pest Note referenced abov for the specifics..
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Come to the UC MGCC Program's Great Tomato Plant Sale
Walnut Creek 4/2&9, Richmond 4/9, and Antioch 4/16
Click for locations and plant lists!
Dozens of heirloom tomatoes & vegetables chosen especially for Contra Costa
Note: The UC Master Gardeners Program of Contra Costa's Help Desk is available year-round to answer your gardening questions. Except for a few holidays, we're open every week, Monday through Thursday for walk-ins from 9:00 am to Noon at 75 Santa Barbara Road, 2d Floor, Pleasant Hill, CA 94523. We can also be reached via telephone: (925) 646-6586, email: ccmg@ucanr.edu, or on the web at http://ccmg.ucanr.edu/Ask_Us/ MGCC Blogs can be found at http://ccmg.ucanr.edu/HortCoCo/ You can also subscribe to the Blog (http://ucanr.edu/blogs/CCMGBlog/).
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