The chemistry behind oxalic acid
As an acid, oxalic acid is corrosive. It is used as an industrial bleaching agent and heavy-duty cleaning product. Apparently, it works especially well on removing rust. Oxalic acid is also classified as nephrotoxin, which means it can damage your kidneys. Oxalic acid, in the form of calcium oxalate, is the most common ingredient of kidney and urinary tract stones. Oxalic acid can also cause joint pain. At high concentrations, oxalic acid really is deadly. According to the National Institutes of Health, lethal doses range from 15 to 30 mg, though an oral dose of 5 mg has been fatal.
In each of these cases, it is the amount of oxalic acid being ingested that is the problem. The levels found in many foods are too low to cause problems. Bottom line, a 150-pound person would need to eat approximately 12 pounds of rhubarb leaves for it to be dangerous. And spinach leaves contain more oxalic acid than rhubarb leaves. That's why your teeth may feel funny after eating spinach. It's oxalic acid crystals binding with any nearby calcium to create calcium oxalate crystals. These crystals stick to your teeth for several minutes to an hour.
Oxalic acid in nature
Oxalic acid is found in a surprising number of food plants that we eat every day. The trick is in the concentration. In fact, oxalates can be toxic to plants, too, but plants bind those oxalates up in crystals that they then use as tiny spears to defend themselves against herbivores. These specialized cells are called idioblasts. Oxalic acid is formed when plants burn sugars and carbohydrates as fuel.
Oxalates are also used to balance calcium levels, within the plant, by binding to calcium molecules. This is why some people say eating high levels of oxalic acid can interfere with healthy bones and teeth, but, again, you would have to eat an awful lot—over a long period of time—to cause any real problems. By the way, our bodies produce oxalic acid out of Vitamin C, on purpose. Also, cooking plants that contain oxalic acid has not been shown to reduce oxalate levels.
Armed with this information, I went out to my rhubarb plant and broke off a young leaf and ate it. The flavor was actually pretty nice, something akin to spinach, but lighter. And I lived to tell about it.
by UC Master Gardener Kate Russell
Photo: South Valley Magazine
This article first appeared in the January 5, 2018 issue of the South Valley Magazine.
And what to do this month in your garden
Eggplants come in all shapes, sizes, and colors. Japanese and Chinese varieties are usually long and narrow and can be lavender to deep, dark purple. Indian (sometimes call baby eggplant because they are so small) are reddish purple and are great in curry, stuffed, or roasted. Some Thai eggplant are actually green when ripe. “Fairy Tale” are very small, can fit in the palm of your hand, and are a beautiful purple with white stripes. They are very tender and great for grilling. “Little Green” has pale-green skin and is mild and very creamy when cooked.
Now is a great time to plant your eggplant (from transplant). They are easy to grow, even in containers. They grow best in a warm, sunny location with at least 6 or more hours of direct sunlight. They should be spaced about 24-36 inches apart.
They are upright growers but will need support once they start fruiting to hold all the weight of the abundant fruit. When planting, mix in a good organic compost and some slow-release fertilizer. With proper care and feeding, many varieties will keep producing well into the winter months – I have often served them with my Thanksgiving dinner.
This month in your garden
- Check irrigation and mulch: If you haven't already inspected your irrigation system or put down that very important layer of mulch, it's not too late. Do it before the summer heat sets in.
- Deadhead roses, salvias, and dahlias to encourage continual blooming. Remove spent buds from camellias, rhododendrons, and azaleas.
- Control earwigs which feed on soft plants and can cause significant damage. Trap them by setting out moistened, tightly rolled newspaper at night and then discard it in the morning.
- Fire blight shows up in the spring. It causes blackened branches and twigs that look like they have been scorched. It often affects fruit trees such as apple, pear, loquat, and quince; as well as toyons, hawthorns and crabapples. It is spread by insects, rain, and pruning. If left unattended it can kill the tree. Prune the infected branch about 8-12 inches below the visible damage.
- Prune suckers from rose bushes. It can be difficult to tell the difference between suckers and basal canes. They both shoot straight up with vigorous growth. Suckers grow from below the bud union. Basal canes originate at the bud union and should be left on – they are the best wood on the plant.
- Don't forget to deep water your trees (especially if they are less than three years old). We are likely moving back into drought conditions; deep watering once a month will help protect those environmentally-important fruit and ornamental trees. It takes much less water to preserve established trees than it does to start new ones!
Plant this month
- By seed: arugula, beans, beets, Brussels sprouts, corn, cucumber, melons, summer and winter squash.
- By transplant: arugula, basil, beans, beets, corn, cucumber, eggplant, melons, mint, peppers, summer and winter squash, and tomatoes. Local nurseries should have a good supply of most of these.
Too much fruit? If you have an abundance of fruit and have already “over-shared” with your neighbors, contact Village Harvest. They offer volunteers that will pick your fruit and then donate it to a worthy food bank.
by UC Master Gardener Rebecca Jepsen
This article first appeared in the June 10, 2018 print issue of the San Jose Mercury News./h3>
Chicory is commonly used as a coffee substitute
Chicory is a woody perennial that comes in many different varieties, depending on the cultivar used: roots (var. sativum) and leaves (var. foliosum) are the most common. Chicory, occurring naturally, can indicate compacted soil. Luckily, its deep taproot help breaks up that compacted soil, plus it's drought tolerant!
Chicory as food
Chicory is a highly versatile plant. Its slightly bitter leaves are used in salads, the buds can be blanched, and the taproots are frequently roasted and ground up as a coffee substitute. You can reduce the bitterness by changing the cooking water two or three times. Roots are harvested before flowering stems emerge. These roots can be cooked and eaten the same as carrots or parsnips, ground into flour for bread, or used as a coffee substitute. Plus, chicory contains twice as much of the cancer-fighting, heart-healthy polyphenols found in spinach.
A member of the daisy family (Asteraceae), chicory (Cichorium intybus) is one of those large, gregarious groups that may surprise you. For example, curly endive, Belgian endive, and radicchio are all types of chicory. Lettuce and dandelions are close cousins, while chicory's distant cousins include sunflowers, artichokes, and yarrow. Also known as cornflower, bachelor's buttons, coffeeweed, blue daisy, and wild endive, chicory's flowers are composite, and leaves are normally toothed or lobed. Plants grow 10 to 40 inches tall. Flowers appear July through October.
How to grow chicory
In our planting zone (9b), chicory is a cool season crop that can be started in January and February for an early summer crop, and again in July or August for an early winter crop. This gives the seeds time to get started before the weather turns too hot or too cold. Summer's heat causes chicory to bolt, but a light frost actually adds just a touch of sweetness. Seeds should be planted 1/4 inch deep and thinned to 12 inches apart. Avoid overhead watering, as the leaves are prone to rotting.
Chicory pests and diseases
Despite its rugged nature, there are some pests and diseases that can impact chicory. Bacterial soft rot, damping off disease, fusarium wilt, white mold, anthracnose, and downy mildews are all diseases that attack chicory. Aphids, cabbage loopers, beetles, leaf miners, thrips, and slugs and snails may feed on your chicory plants.
Chicory grows like a weed. Once established, you can pretty much ignore it until you decide to harvest whatever part you have a hankering for. And, hey, even the flowers are edible!
by UC Master Gardener Kate Russell
Photo: South Valley Magazine
This article first appeared in the December 17, 2017 issue of South Valley Magazine./h3>
I have to tell you, I literally hit pay dirt. I planted one Echium fastuosum, “Star of Madeira”, and it is not only a major bee-magnet, it is absolutely stunning! With hundreds of profuse bluish-purple flowers atop tall spikes that tower above the attractive, variegated foliage, it has become the focal plant in my garden. It is also a favorite for my hummingbirds and butterflies.
When I planted it about three years ago from a 2-gallon pot, it was about a foot tall. Now It is now nearly 7 feet tall and about 5 feet across. It would actually be bigger but I continue to prune it so that I have room for the apples and avocados that are planted nearby.
There are more than 60 species of Echium, some are native to North America, others are from Europe and the Macaroneisa. Although some are grown as food for humans, butterflies, or moths, most Echium are grown as ornamental plants.
Probably the most common varietal you will find in the Bay Area is Echium candicans, “Pride of Madeira”. Its silvery-green foliage sports masses of very blue/purple blooms from early spring to mid-summer. It can easily grow 8 feet tall by 6 feet wide and is a heavy self-seeder, so you may want to dig up and gift most of those starts.
Echium amoenum, “Red Feathers”, is for those of you who want something a little more on the compact side. They grow only about a foot and half tall by about 6-to-8 inches wide. This plant is known to thrive on neglect, is suitable for clay soil and can handle cooler climates. The red feathery blooms attract an array of bees and butterflies. Although it is known to be short-lived, it will reseed itself if you resist deadheading all of the dried blooms.
Echium vucanorum, is a truly beautiful, and quite rare, white blooming varietal. It is native to a tiny West African island named Fogo. It will quickly grow to 6 feet high and wide and may do best with some afternoon shade in hotter areas.
And for maybe one of the coolest plants you can grow, try Echium wildpretii. It is a biennial from the Canary Islands. In its second year, it will send up tall spikes (up to 7 feet) of gorgeous dark pink/reddish flowers. Let it fully mature so that it can reseed and keep on going … the bees and birds love this one!
I believe every garden and every landscape should have at least one bee-friendly Echium. Most need a good bit of room to thrive and grow and at least six hours of sunlight per day. They are very drought-tolerant but do need regular watering for the first couple of years in order to get established. They prefer well-draining soil, but some can tolerate relatively poor conditions.
Many Bay Area nurseries carry several options. You can also do a Google-search of Echium to find unique and rare varieties. This may become your new favorite plant.
by UC Master Gardener Rebecca Jepsen
Photo courtesy of Rebecca Epsen
This article first appeared in the April 22, 2018 print issue of the San Jose Mercury News.
By planting several varieties of “attractor plants” you can invite the good guys in to fend off the bad ones without using harmful, toxic chemicals; certainly not something you want near the food you and your family are going to eat.
Lady Bird Beetles (ladybugs) are good friends to have around if aphids are a problem in your garden. They can eat about 50 aphids per day. They are very attracted to alyssum “Goldkugel” and “White Night”, yarrow, ajuga, marigold “Lemon Gem”, fennel, and sunflowers.
But your new best friend might be the lesser-known lacewing (the aphid lion). It may be so small you don't even see it, but it eats 20 times more aphids each day than a ladybug. You are almost certain to attract them by planting yarrow, dill, cosmos, coriander, Queen Anne's lace, and flowering mustard.
Bees are essential when growing edibles. More than 30 percent of all the food we eat is pollinated by bees. I am happy to report that I have the beautiful buzz of bees in my backyard year-round. To keep them happy I have planted a dozen varieties of salvia. Not only are they beautiful, they are easy to grow, come in all sizes and colors and take very little water once established. What's not to love? And, although most prefer full sun, there are many options that thrive in part sun to fairly deep shade.
Another favorite that both my bees and I love is lavender. It comes in all shades of purple (from very dark to pale purplish-pink) and even white. So why settle for just one? Don't have a lot of space? Choose one of the several dwarf options.
Rosemary is not only hardy, drought-tolerant, fragrant, and great for cooking, it attracts bees even in our wet winter months. For other flowering plants that are attractive as well as attracting try black-eyed Susan, calendula, purple coneflower, butterfly bush, bee balm, and sedums.
Hoverflies, also known as syrphid flies, look like small bees but literally hover over a plant or flower and then quickly dart away. By watching their movement you can easily distinguish them from bees. They do not sting, and they eat aphids, mealybugs, and thrips. They also like yarrow, alyssum, dill, garlic chives, and fennel. But try adding dwarf alpine aster, feverfew, statice, lemon balm and parsley to keep them healthy and happy.
There are many varieties of parasitic wasps. Again, at first glance they may look like a bee, but, if you look closer you will see that they have few if any, hairs. Bees are pollen collectors so are generally quite hairy. Wasps feed on tomato hornworms, cabbage worms, beetles, stink bugs, squash bugs, fly larvae and more. These little guys are great in the garden, and again they do not sting. Plant buckwheat, lemon balm, creeping thyme, cosmos “White Sensation”, lobelia, zinnia “Liliput”, parsley and Linaria.
Your garden is its own ecosystem. It takes time to build a healthy, thriving, environment that can mostly take care of itself. So, be patient, strive for diversity and trust me, if you plant it … they will come.
by UC Master Gardener Rebecca Jepsen
This article first appeared in the May 27, 2018 print issue of the San Jose Mercury News.