Beware the sap of the giant hogweed

Share this:

I read about a terrible weed called Giant Hogweed that has just been discovered in Ingham County. It is really new and I need information because I think that it could be growing at my house, too.
Sorry to disappoint but hogweed was originally introduced into Michigan in the 1890’s. It is Eurasian in origin and was first brought as seeds to the Upper Peninsula.

This is a plant that could grow to 20 feet tall, but in Michigan, it rarely exceeds 12 feet. But its size is not the problem.

If the plant’s sap gets on you and you are in the sun, your skin develops severe blisters that take a long time to heal. When they do heal, the skin is permanently discolored a dark purple-black color. If the sap gets in your eyes, you get severe corneal burns and there is a big chance that you will be permanently blind.

There is a tiny chance that you might find it growing. Notice that word, tiny. It has already been found in the last several decades in 13 Michigan counties, mostly in small numbers.

Hogweed has enormous stems that are ribbed, 2- to 4-inch diameter stem that is speckled or mottled with reddish-purple spots. The stem is also covered by coarse hairs and there is a very visible ring of hairs at the base of where the leaves attach to the stem. Leaves are green, shiny and deeply cut for a roughly jagged appearance. They can be as much as 5 feet across.

When hogweed flowers, the white flowers look like Queen Anne’s lace or wild carrot on steroids. The flat-topped umbels are up to 2-1/2 feet wide. Seeds are tan, oval and flat and measure a little over an inch long.

There are several native plants that have a passing resemblance to giant hogweed. They are wild parsnip, Angelica, poison hemlock and Queen Anne’s lace. Some people see a small likeness to pokeweed. Before going crazy, click here and look at the information on giant hogweed. This will help you determine if you actually have giant hogweed or a really good imagination.

I have the sweetest little purple leaf plum tree. I looked at it today and I saw dozens of big black, dry, cracked swellings on many branches. Some of those branches were either wilting or dead. I love this tree and whatever happened to it, literally just happened overnight. How do I fix this and make those black things go away?
You may love your decorative plum but you two have not been spending quality time together regularly.

Your plum has a fungal disease called black knot. When you can see the black knots and the withering branches, those galls have been there for at least two years.

Black knot affects ornamental, wild and edible plum trees. Occasionally, cherry trees are also affected. The plum trees that have particularly bad problems are purple leaf plum, sand cherries and European edible plums like Stanley. It is a disease that is easy to identify but hard to treat successfully.

With the increase in air humidity in the last dozen years, all fungal diseases have gotten more prevalent. The black knot fungal invasion starts with the development of small, light brown swellings on the current year’s or last year’s growth. The next year, those swellings grow in size and become olive green. During the season, they become black and corky and begin to cut off the nutrient flow to the branch.

Galls need to be pruned out during the winter so they do not spread. At least 6 inches of wood plus the gall must be cut out. Burn or bury the galls. Spraying is often not successful. But chlorothalonil can be sprayed when the trees are dormant in the spring and again when the flower buds color up.

But this could be goodbye to Sweetie.

About Gretchen Voyle 51 Articles

Gretchen Voyle is the MSU Extension-Livingston County Horticulture Educator. She can be reached at (517) 546-3950.