Pokeweed--A huge and Toxic Weed

In my SF Chronicle Column for November, I reported on a weed that has been sighted in San Francisco. It's a native in the  Eastern part of the U.S., so I was surprised to find it here, but there it is. I also saw one down the Peninsula this summer, though I forget just where. 

The plant is large, 4-10 feet tall, and most parts and stages of it are toxic to most mammals. I described it in my column, but was unable to get a photo of it into the print version. However, I can show a photo here. This is an image of a stem of berries. Botanists call this kind of flower or fruit-bearing stem a raceme. The berries are dark purple. When they are ripe, their stems and the longer central stem of the raceme are usually bright pink. The stems of ripe berries are the most recognizable parts of the plant. 

Pokeweed berries

Photo by Andra Sadoun

You may find it surprising, given the toxicity of this plant, to know that it has long been a part of the diet of rural people in the South and eastern-central parts of the U.S.one of the young greens gathered and eaten in spring.  Only the leaves of very young plants are eaten, and they must be boiled two or three times, with the boiling water drained off of them between boilings and after the last one. This dish is called "poke sallet." (It important to know that the word "sallet" derives from an old English word that meant cooked greens, not salad, as the raw leaves would be toxic.)

The berries are toxic, and eating only a few has killed small children. Though some say the seeds are the most toxic part, it hardly seems worth the risk to try them. Birds seem immune to the berry toxin, so the fruit is eaten by many kinds of birds, including Northern mockingbird, mourning doves, and cedar waxwings. Raccoons and possums may also be able to eat the berries, though most mammals cannot.

The most toxic part of all is the root. The plant is perennial, likely to regrow from last year's roots, so the best way to get rid of it is to dig it out. Wear gloves, as the toxin can enter through skin. Then pick up any fallen berries you see, and watch for seedlings. (The young plants are sort of nondescript, with large oval, pointed leaves.)

How did the weed get here? Presumably from bird-planted seed, but it's possible the seed was assisted by some other form of transportation. It could have stowed away in tire treads or shoe treads. While there are domestic varieties, are grown as ornamentals, their leaves look different from the wild plant. (The ornamental varieties are  ‘Silberstein’, which has pale, cream-colored leaves with green spots, and ‘Sunny Side Up’, with yellow-green leaves.) The ones being found in the Bay Area seem to have normally green leaves, meaning are not escaped ornamentals.

 


Bay Area Citrus in Great Danger

If you have citrus trees in your garden, or know someone who does, listen up. A pest insect that has wiped out half of the citrus crop in Florida is spreading in California and has reached the Bay Area. Last year, a new quarantine area was created in the San Jose region, because the pest was found in trees there. Now the most recent quarantine area covers the northern peninsula and a swath of the southern part of San Francisco.

Lemon tree IMG_8366 copy

Lemons on a Healthy Lemon Tree in San Francisco

The insect itself will not kill the tree, but it often carries a deadly disease, and if a particular individual insect is carrying that disease, it will infect the tree while it is feeding. And then there is no cure. Other Asian citrus psyllids will pick up the disease from that infected tree, and will spread it.

So far, none of the insects found in our region have been carrying the disease, but it seems like only a matter of time till one does. Scientists are looking for a cure, or a way to breed resistance to the disease into citrus trees, and would like to buy as much time as they can by keeping the problem in as small an area as possible.

What to do? Inspect your trees. Spring is a good time to do it, since it is a time when there is much active growth on citrus. Look carefully at as many of the growing tips, with their small, new leaves, as you can. The insect, which is called the Asian Citrus Psyllid, or ACP, lays very small yellow-orange eggs in new growth. They will be easier to see with a magnifying glass. The eggs hatch into yellow nymphs that average sesame seed-sized. They are also distinctive in having long, white "tubules" with bulbous ends that extend from their bodies. The adults are aphid-like, mottled browns, and stand with their rear in the air, heads down, sucking sap.

ACP nymphs 002

Asian Citrus Psyllid Nymphs

ACP adult 001 Rogers

Asian Citrus Psyllid Adult Feeding on Citrus Leaf

If you find the insect on your tree, and are not in an area already quarantined, you should call the California Food & Agriculture (CDFA) Exotic Pest Hotline at 800-491-1899. If you are within  the quarantine area already, you should try to kill the pest.

To see an interactive map of the quarantined areas and more photos and learn the best ways to control the pest, see the following UC  website: http://ucanr.edu/sites/ACP/Homeowner_Options/

Also, be sure to buy citrus only from responsible sources. (Major citrus tree growers are now growing trees for the market only in covered production areas that the pest can't get into.) Don't accept plants, cuttings, or grafting material from other gardeners.

And if you are in a quarantined area, don't take any leafy branches outside of it. (You can share your fruit outside of the quarantined area if it doesn't have any stems or leaves attached.)

The insect can also infest some plants that are related to edible citrus, like calamondin (xCitrofortunella microcarpa), box orange (Severinia buxifolia), orange jessamine or orange jasmine (Murraya paniculata), and Indian curry leaf (Murraya koenigii). They should also be inspected and are subject to the same quarantine rules.

The disease we are trying to avoid, and that I hope we never see, is Huanglongbing, or HLB. It is also known as yellow shoot or yellow dragon disease. The leaves of infected trees have yellow blotches, usually starting in one section of the tree. The blotches don't look like most nutritional deficiencies in that they cross the leaf veins, and are often arranged asymmetrically on the leaf. Fruit develops unevenly, asymmetrically, ripens poorly, with little juice and a bitter flavor. The disease will kill the tree. If it appears, the only recourse at this time is to remove the infected tree before the disease spreads to other ones.

So let's get out there and look now, before it's too late!

HLB Symptoms DSC_1221

Yellow-blotched Leaves of a Citrus Tree Infected with HLB Disease.