Be Careful With Toxic Plants

Toxic plants can be quite appealing.

Plants are so much more intelligent than they get credit for. Many use color, fragrance and flavorful nectar to get insects and animals to disperse their pollen for them. Some provide fruit for animals that inadvertently take and disperse their seeds. Others use barbs or sticky substances to attach their seeds to unknowing animals that take them away. Plants have all sorts of techniques for exploiting those who are more animated than they are. After all, immobility has certain disadvantages.

Because plants can not get away from the animals and insects that eat them, many have developed techniques for being unappealing. Plants that live in deserts where edible foliage is relatively scarce are famous for their nasty thorns and spines, like those of cacti and agave. Hellebore and poinsettia have caustic sap that make them unpalatable. The naturally aromatic foliage of many edible herbs, like rosemary and lavender, is actually intended to repel grazing animals with sensitive noses.

Some plants unfortunately rely on toxicity for protection. Many plants are only partially toxic. For example, apples are intended to be eaten safely by animals that disperse the seeds within, but their seeds are toxic enough to avoid getting eaten by rodents after dispersal. Potato, tomato, rhubarb, asparagus and elderberry plants all produce edible fruits or vegetables, but also have poisonous parts. Some edible fruits and vegetables, like grapes and onions, are edible to humans, but toxic to dogs.

Foxglove, angels’ trumpet, morning glory, yew, rhododendron, azalea, oleander and castor bean are some of the more notably toxic plants often found in home gardens. Wisteria, holly and ivy produce toxic seeds and fruits. Dieffenbachia is a popular but very toxic houseplant. Although mostly safe, toxic plants can be a problem where young children might put things into their mouths, or where puppies are in that chewing phase.

Some Edible Plants Start Out Toxic

Pokeweed is both edible and toxic.

Early American settlers from Europe had a lot to learn about the plants of North America. After their first harsh winter without much food, many were eager to eat the first fresh greens of spring, which was sometimes the very poisonous jimson weed. Those who were not lethally poisoned right away might have hallucinated and told their friends that they could fly, and consequently got burned as witches.

It should be no wonder that some early Americans were hesitant to try tomatoes, which are related to jimson weed. Potatoes are also related, and their fruit, foliage and stems actually are toxic. Pokeweed (unrelated) was probably riskier, since the same young shoots that can be cooked as greens become toxic as they mature. Their poisonous berries, which were used as ink back then, look delicious.

There were other potentially dangerous edibles brought from Europe and other places as well. Rhubarb, which makes such great pies, is petioles (leaf stalks) for toxic leaves. Both American and European elderberries are slightly toxic before getting cooked into jelly or pie. Elderberry juice must be cooked and then given yeast to make wine. Figs and mulberries can be eaten right off their trees, but their sap is caustic enough to be irritating to the skin.

The seeds of apples, pears, peaches, nectarines and apricots can be toxic if too many are eaten. They are not a problem only because they are not eaten. However, apricot kernels can be roasted and eaten like almonds because the cooking process denatures the toxins. Separating the small kernels from the hard shells is much more work than it is for almonds, but they supposedly have great flavor.

Just like for apricot kernels, pokeweed and elderberries, the heat of cooking makes taro edible. The foliage can be eaten as stewed greens. The big and starchy corms (bulb-like stems) are something like potatoes. All parts of taro are toxic while raw. There are actually a few toxic plants that are edible once cooked. For a few others, it is important to know what parts are edible, and what parts are toxic.

Poison Oak Tree

P91229From below, this looks like a shrubby deciduous tree. It is really just a Douglas fir, like those around it. All the defoliated thicket growth is overgrown poison oak. It has likely been climbing the fir tree since it was quite young. Poison oak is not very proficient at climbing bare trunks. It typically climbs into lower limbs, and then into higher limbs before the lower limbs are shed.

No one has bothered to cut this poison oak out of the fir tree because it is not within a landscapes area. That dark margin at the top of the picture is the underside of a bridge, from which, not much of the thicket growth below is visible. The area from which this picture was taken is used for piling greenwaste and parking, where no one is concerned about wild vegetation beyond.

However, now that I sometimes park in that particular parking area, I am finding this mess of poison oak difficult to ignore. There was a similar but even bigger thicket of poison oak up in a redwood tree at the farm, from where it tossed seed into horticultural commodities below. The resulting seedlings added a whole new dimension to weeding the stock. The thicket had to go.

The problem with the thicket in the picture above, although not as serious, is that it too tosses seed into area where people work. Seedlings are likely to grow where greenwaste is processed, and where I sometimes park. Poison oak that grows on the far side of this fir grove will be uncomfortably close to the right field foul line of a ball field that will eventually be restored there.

I have no intention of cutting the poison out of the fir tree. I will merely sever the main trunk at the base, as seen in the picture below. As it deteriorates over several years, no one will mind if it is somewhat unsightly on the industrial yard side. The adjacent fir trees sufficiently obscure it from view from the ball field side. The priority will be preventing seed from proliferating.P91229+

Rhus diversiloba / Toxicodendron diversilobum

P81209This would be a good topic for one of my rants on Wednesday, except that it is too silly for that.

Many years ago, before I started writing my gardening column for our local newspapers, my colleague Brent and I used to exchange funny newspaper gardening articles. Some were obviously not written for local climates. Some were just very inaccurate. Back then, it was done by mail, so the articles were added to anything that we happened to be sending to each other at the time. If I sent him some seeds, I would add an article or a few from the San Jose Mercury News. If he sent my cuttings, he would add an article or a few from the Los Angeles Times. They eventually became the inspiration for my gardening column, when Brent and others told me that rather than making fun of the inaccuracies of the articles, I should provide accurate articles.

One of the silliest that Brent sent to me was an otherwise well written article about star jasmine. Most of the information about it was accurate, until it got to describing the colors of the exclusively white bloom. The article explained that star jasmine bloomed in vivid shades or blue, purple, red, orange and yellow; just about every color except for white!

Well, I topped that with an article about protecting Japanese maples from theft, which sounded crazy even before reading the article. There were three recommendations. The first was to surround the subject Japanese maple with razor wire. Ah, the ambiance! The second recommendation was to dig a hole about as big as a trash can and fill it with concrete with a curved piece of rebar to make an enclosed loop on top, and then chain the subject Japanese maple to it. How about we just do without a Japanese maple in the front yard in a neighborhood where we expect it to get stolen. The third recommendation was to plant poison oak around the subject Japanese maple. Yes, good old fashioned poison oak, Rhus diversiloba, which is also known by the more descriptive Latin name of Toxicodendron diversilobum, and commonly available at . . . . some nursery . . . . somewhere. . . . You know, one of those . . . . garden centers . . . . or something.

Silly? Yes! What is sillier is that poison oak really IS available from certain nurseries that sell native species! What is even SILLIER than that incredible degree of SILLINESS is that one of the so-called landscape companies that I worked for in about 2006 actually procured some for habitat restoration outside of, but adjacent to a newly landscaped area on the banks of where the Guadalupe River flows through San Jose. Poison oak and other native vegetation needed to be eradicated for the installation of the new poison oak and associated irrigation system, because nothing is more natural than supplemental irrigation! Then, the ‘gardeners’ had to conduct regularly scheduled weed abatement so that poison oak growing from seed tossed by the pre-existing poison oak did not grow up and compete with the new poison oak in the new ‘natural’ ‘landscape’. We certainly would not want poison oak taking over the poison oak.

Okay, this is not Wednesday, so I will finish this rant.

Poison oak happens to provide some of the best orange and red autumn foliar color in our region where almost all of such color is simple yellow. Where it is out of the way and not bothering anyone, it is sometimes left to climb high into trees, where it colors almost as well as flowering pear. Yes, it is pretty, but I will not be planting any of it.P81209+