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Plants to Avoid If You Can

Posted on Tuesday, July 19, 2022 · Leave a Comment 

This is the time of year when wild parsnips are in full bloom. They stand anywhere from two to six feet tall, and are topped with clusters of tiny flowers facing upward and arranged in a flat cluster called an umbel. The blossoms are similar to those on Queen Anne’s lace, but yellow.

 

Wild parsnips often grow along the roadside. Many people are easily burned by the sap.

Avoid wild parsnips because you can get terrible burns from the sap of this plant. When the sap on you is hit by bright sunshine, most people develop painful blisters. This is unfortunate, as this common plant is spread by seed, often creating large patches in fields and along roadsides. If you get sap on you, wash it off with soap and water immediately, cover the area, and stay out of direct sunshine for 48 hours.

 

How can you get rid of wild parsnips? Wild parsnips are biennials – meaning they die after blooming in their second year. I’ve read that mowing a patch of them right after they bloom (but before they produce seeds) will get rid of them, but only if you do this for three to five years. Presumably the repeated mowing is needed to kill plants that come back from seeds that did not germinate in year one. 

 

Giant hogweed is an invasive that can burn you with its sap.

Giant hogweed (Heracleum mantegazzianum) is in the same family as parsnips, but is bigger, harder to get rid of, and even more toxic. I saw it for sale some 20 years ago and was intrigued by its size (6 to 12 feet tall) and blossoms that are up to three feet across. I bought it and planted it, having been told that it was not a perennial, though it is.

 

Even though I didn’t know its sap could cause burns, I quickly decided that giant hogweed was not a plant I wanted – it popped up 50 feet away from where I planted it, and could grow in full sun or full shade, wet soil or dry. I decided it had potential to be a thug.

 

At first I just cut off the flower heads before they produced seeds, but in year two or three I decided to pull it by the roots, I was lucky that I was able to get out the roots which can go down two feet or more. And even more fortunately, either I did not get sap on me, or I am not allergic to it. It is not widely distributed in New England, though it is a real pest in parts of California and elsewhere.

 

I was less fortunate when it came to getting rid of the Japanese butterbur (Petasites japonicus) I purchased long ago. I was told that yes, it could run, but it was easy to contain with a lawnmower or a stream. Not so. This plant can send roots 20 feet or more, then send up new plants. It is an aggressive plant that will smother almost any other. It likes moisture, and does well in shade as well as sun. 

 

Depending on the variety, this plant can produce clumps of huge leaves that stand up to five feet tall. It has small flowers that erupt from the soil before the leaves. The roots go down deep and break easily, making it tough to remove. In its native Japan, it is considered an edible, but I have no interest in eating it.

 

I have lost control of our Japanese butterbur. It crossed the stream and gone under the lawn to other beds, and generally become a pest. Even though it is interesting to look at, enough is enough! I wish I had never bought it!

 

Buttercups are pretty but tough to control

Another pest I have will surprise you, perhaps: buttercups (Ranunculus repens). Like some of the others mentioned above, at first I welcomed this bright harbinger of spring which displays cheerful yellow blossoms. But it has become a problem because it spreads not only by root, but by seed, and once established it is difficult to weed out. And it will choke out other plants. It is glorious in bloom, but very tenacious. If you have moist, rich soil in part shade, watch out. I’d advise removing it early before it starts crowding out other plants. This one is native to Europe, but there are native species that are not a problem, I am told.

 

Years ago a friend gave me some iris that had the roots of goutweed (Aegopodium podagraria) tangled in with the iris roots. It quickly took over the iris bed, choking out everything else. A native of Asia and parts of Europe, it can form a dense mat that outcompetes everything else. The roots are brittle, and thus hard to remove. Even a scrap of root can start a new plant.

 

Goutweed will outcompete any other plants and is difficult to eradicate

I dug out all the goutweed, took away the soil down to 12 inches and replaced the soil after putting down a heavy weed mat. Still … 5 years later it crawled out from under the mat. If you have it, accept you will probably always have it, though with persistence and a good weeding tool, it is possible to control. But I wouldn’t buy a house that has it!

 

A variegated form of goutweed called ‘Snow on the Mountains’ has green and white leaves and was sold as a groundcover in the past. But sometimes it reverts back to the more aggressive all-green form and tries to take over the world. So avoid both forms.

 

Let’s face it: plants take advantage of us if they can. We like good looking, interesting plants, so they put on a good show. But among the good ones, there are those aggressive thugs that deserve no mercy. All you can do is be attentive, and act quickly when a new plant starts to take over your gardens.

 

Henry is the author of 4 gardening books, and a lifetime UNH Master Gardener. Reach him at PO Box 364, Cornish Flat, NH 03746 or by e-mail at henry.homeyer@comcast.net.

 

 

 

Filed under Article · Tagged with buttercup invasive, goutweed, Japanese butterbur, wild parsnip

Three Plants to Avoid

Posted on Tuesday, August 18, 2020 · Leave a Comment 

Three plants you don’t want on your property are wild parsnips, purple loosestrife, and Norway maples. The first causes severe skin reactions in many people, the second can take over our wetlands, and the last can out compete our native sugar maple – and eventually take over our woods.

 

Wild parsnip is in bloom now. It’s a tall plant, 24 to 60 inches, and has yellow blossoms arranged in flat flower panicles at the top of the stems. It looks a lot like Queen Anne’s lace. It is, genetically, the same plant as garden parsnips, but has escaped and become a weed. Some people are horribly allergic to its sap. Here’s how you and your kids can stay safe.

 

Wild parsnips often grow along the roadside. Many people are easily burned by the sap.

Learn what it looks like, and avoid it. Sap from the stem, if on the skin and exposed to direct sunlight, can cause horrible burns. Not everyone reacts, however. Assume you do. If you get sap on you, go inside IMMEDIATELY and wash the affected area thoroughly.

 

Wild parsnip has a 2-year cycle. The first year it stays low and develops a deep tap root. The second year it bolts and produces a tall flower stalk. If you have a field of wild parsnip, get it mowed before the flowers set seeds. And re-mowed until it gives up.  The sooner you mow it, the less likely the flowers are to produce viable seeds after they are cut down.

 

First year plants growing now will send up flower stalks next year. And each year, for a while, seeds in the ground will grow new plants. But each year there will be fewer, and eventually they will be gone.

 

This is the time of year when swampy areas often are ablaze with tall, pink-purple flowers that dominate the wetland. These are the flowers of purple loosestrife ( Lythrum salicaria), an invasive plant that you should not encourage – but that you probably can’t get rid of once established.

 

But why worry about it? It’s such an aggressive grower that it out-competes native plants. It moves into shallow wetlands where fish and frogs lay their eggs among native plants, creating dense monocultures. Biodiversity is healthy for the environment, and purple loosestrife inhibits many other kinds of plants from growing.

 

Mature plants develop massive root systems can’t be dug out. They also develop long side-roots that will easily break off and start new plants if you try to remove the clumps.

 

A big clump can produce up to 2.7 million seeds in a year. And like time-release cold capsules, the seeds become active over time, not all in one year. And since they grow in wetlands, you can’t use herbicides.

 

If you have big, established plants the best thing to do is cut them down every summer, just above the soil line, preferably more than once. Do it now, and this should prevent them from producing seeds this year. It will also reduce the vigor of the plants. It won’t kill them, but it will keep them from spreading.  A string trimmer will do the job, if you have one.

 

Purple Loosestrife can take over a wetland.004

First or second year plants often show up in my garden near my stream, but can be hand-pulled. Look for plants with a square stem that quickly get 18 to 24 inches tall, and may have a reddish-brown tinge to their stems. Older plants get to be 3 to 7 feet tall or more. Leaves are long and narrow with a smooth edge, and they attach directly to the stalk – without an attachment stem. Leaves generally appear in pairs, across from each other on a stalk. Many flower stems arise from the main stem.

 

Beetles from Europe have been introduced in some places to eat purple loosestrife, reducing populations by as much as 90%. But those beetles are not available for purchase – at least not yet. So if you have it, cut the plants down. Today!

 

Lastly, there is the Norway maple, a maple that will thrive anywhere – wet, dry, shady or sunny. It sends roots long distances, sucking up water and soil nutrients. It produces massive numbers of seeds, seeds that blow or wash away and end up in our woods. It can out-compete our native sugar maples, and will. Fortunately, it is now against the law to propagate, sell or transport these bad boys.

 

White sap oozes from Norway maple leaf stems

The most popular Norway maple is a cultivar called “Crimson King’. It has leaves that are a deep purple – almost black. Many cities and homeowners bought these 50 years ago and installed them. Removing them is difficult and expensive.

 

Here’s another problem: Crimson King is a hybrid, and its seeds rarely produce trees with that distinctive purple color. So they pass themselves off as sugar maples.

 

The leaves are a bit bigger and wider than sugar maples, but you can I.D. a Norway maple by picking a leaf. Look at the place where it snapped off: if it oozes a white sap, it is a Norway maple. If you have one, please consider having it removed. Your great grandchildren’s maple syrup depends on it!

 

Saving the world starts with small steps. If we each do what we can, we can leave the world a better place.

 

Henry is a longtime Master Gardener and the author of 4 gardening books. Write him at henry.homeyer@comcast.net or P.O. Box 364, Cornish Flat, NH 03746.

Filed under Article · Tagged with Norway maple, purple loosestrife, wild parsnip

Plants to Watch Out For

          If you have a wet area or a stream on your property, you might be seeing some very pretty tall pinky-purple flowers blooming now, or soon. Those are purple loosestrife (Lythrum salicaria), an invasive plant that you should not encourage. Mature plants develop massive root systems and can produce up to a million seeds in a year. It’s one of several plants you should watch out for.

          So what can you do? First, learn to recognize purple loosestrife when it first grows, even before blooming. It has a square stem, and it is often reddish or brownish at the base. The leaves are long and thin. Each year I try to find time to cut back the stems more than once, reducing its vigor and preventing it from blooming. I pull new plants, but the established ones can’t be weeded out.

Purple loosestrife came from Europe long ago, and there it is not a problem – it evolved along with insects that eat it and keep it from becoming a pest. One of those beetles has been approved for release in the United States and is helping to control loosestrife in some places, but the beetles are not for sale. By cutting it back, I am acting like a big beetle.

Giant hogweed

Another bad actor is giant hogweed (Heracleum mantegazzianum). It is a huge plant – often more than 6 feet tall, with huge palmate leaves (shaped a bit like maple leaves, or your hand) and numerous small white flowers arranged on umbels (umbels are like the stays of an umbrella) that can exceed 3 feet in diameter. I bought one once, before I knew it was invasive. It can grow anywhere – sun or shade, wet or dry – and has a tap root that goes down two feet or more. Worse yet, the sap is highly toxic to many people and can create severe burns and even scars – particularly if you get exposed to it in full sun.

Fortunately, I am not allergic to hogweed, and I was able to rid myself of it by digging it out with my long drain spade, a shovel with a blade that is only 6 inches wide, but 16 inches long. On the other hand, it is a fabulous looking plant and wish I could safely grow it. It is on the invasive species list in many states.

Wild parsnip

A similar plant growing by the roadside right now is wild parsnip (Pastinaca sativa). This, too, has a sap that can burn the skin of many people (but not me). It only grows four feet or so tall, and has a yellow blossom like Queen Anne’s Lace. It is related to carrots – and giant hogweed. According to Sam Thayer’s wonderful book, The Forager’s Harvest, the tall plant we are seeing now is biologically identical to the parsnips we plant in the garden. It is a biennial plant, and Thayer eats the first year wild parsnips, but explains the second year roots are not edible. He states that wild parsnips look a lot like water hemlock, which is extremely poisonous. So do not take any chances!

Stinging nettle (Urtica dioica) is another pest – but one that has its virtues. It can grow almost anywhere, but does best in rich, fertile and moist soils. It has tough little hairs that act as hypodermic needles, delivering a cocktail of chemicals that sting and can produce a rash. Cooking or drying the leaves, however, eliminates the sting and nettles have a long history as an edible plant and medicinal herb.

Stinging nettles with flowers

Nettles can be cooked and eaten like spinach early in the spring. At this time of year the stems and leaves have gotten tough and are not recommended for eating. The plant itself gets to be 5 to 8 feet tall with leaves in opposite pairs that have toothy margins. It is very nutritious – it is up to 25% protein when dried. When dried, it makes a tea that I don’t like very much. Nettles are a good source of Vitamin C and A. I generally leave stinging nettles alone, though I pull them, wearing gloves, if they get into a flowerbed or too close to a path.

Three lovely garden plants that I grow have potentially poisonous side effects: castor bean (Ricinus communis), angel’s trumpet (Datura spp.) and foxglove (Digitalis purpurea). All three have poisonous seeds and (to a lesser degree) leaves. I don’t worry about them because I can’t see anyone – even a child – eating them. Castor beans and angel’s trumpet both have spiny coverings on their seed pods, and foxglove plants have very tiny seeds.

Castor beans can be used to make ricin, a very poisonous powder that can be fatal if inhaled or ingested. In 2013 a crazy guy sent ricin in a letter to President Obama. Fortunately, like kings of old who had tasters, he doesn’t open his own mail. But the plant is big, with palmate leaves in tones of red or bronze. I find it easy to start from seed.

Foxglove

Angel’s trumpet is my substitute for Oriental and Asiatic lilies, which are so badly attacked by lily-leaf beetles that hand-picking daily can’t keep them looking good. Unlike the lilies, it blooms all summer! It comes in white and purple-flowered varieties; the white ones are much more vigorous.

Foxglove is an old favorite of mine. It’s a biennial that produces pink-purple blossoms on tall stems. If you let it, it will drop seeds to the soil, and, in two years will bloom again unless you have s thick layer of mulch, which will inhibit the seeds.

Knowing your plants – and any potential negatives – is important, especially if you keep animals who are likely to nibble on your plants.

Henry is the author of 5 books. His websites are www.Gardening-Guy.com and www.henryhomeyer.com.

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