Category Archives: Weeds

Pokeweed, Pokeweed Everywhere

After writing an article about common pokeweed (Weed du Jour – Common Pokeweed), I was especially aware this year of how many pokeweed plants were popping up in the yard and garden. It seemed like every time I turned around there was another pokeweed plant growing somewhere.

While I know that pokeweed is spread by birds eating the berries, I didn’t think there was that much pokeweed growing in the area for the birds to eat.

How wrong I was!

Pokewed

Pokeweed

While pokeweed can hide a little in the summer, blending in with other plants and weeds, in the fall it becomes more obvious. By this time the plants are the size of small trees. The stems turn a reddish color and the clusters of berries hang down, covered with fruit that are dark purple bordering on the edge of black when ripe.

I’ve come to realize that pokeweed is everywhere here is south-central PA! From vacant lots to hedgerows to untended gardens and yards, large pokeweed plants are coming out of hiding, filled with berries. The birds are having a feast and the seeds are being spread, ensuring that I’ll be pulling up more pokeweed next gardening season. Since each of the berries contains 10 seeds, the birds don’t have to eat too many to spread a lot of pokeweed throughout the area!

Pokeweed Berries

Pokeweed Berries

As if to confirm my conclusions, I was thinking about this post while driving and all of a sudden a bird dropping hit the windshield. Unlike most bird droppings, this one was a bright purple/red color. There are no berries around at this time of year that would give this color to a bird’s droppings except for one – pokeweed!

When a weed seed is spread by birds, there’s not  much that you can do to prevent it from making its way into the garden. The only thing to do is be diligent with the hoe and keep the plants from getting established. That’s certainly the case with pokeweed!

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My Pigweed’s Magic!

Sometimes you see something in the garden that makes you shake your head and say, “What?!?”

I had this experience recently. I was checking the vegetable garden and I was amazed at how good all of the plants looked. There was almost no insect damage on any of the plants and I haven’t used any insecticide this year. I thought it might be because it hasn’t been too hot (until now) and we’ve also had a steady supply of rain. If plants aren’t stressed, they can often ward off insect damage.

Pigweed Growing Next to Beans with Perfect Leaves

Pigweed Growing Next to Beans with Perfect Leaves

I then noticed that there was some redroot pigweed (Amaranthus retroflexus) growing in the garden. This is a common weed in the summer months. But what surprised me is that while the beans, peppers, zucchini and tomatoes looked great, the pigweed looked like an army of insects had attacked it. The leaves were full of holes! I checked the weeds and couldn’t see any insects but the holes were clearly insect damage.

I’ve never had a vegetable garden with so few insect holes in the leaves of the vegetables and I’ve never seen pigweed with so many holes! I did some checking online and some organic sites recommend letting a few pigweed plants grow with your peppers because leafminers prefer to attack the pigweed. I’ve never had a leafminer problem but maybe pigweed is a prefered host for a lot of other insects as well.

"Magic" Pigweed Close Up

“Magic” Pigweed Close Up

I’m not sure what’s going on but it’s obvious that the pigweed is somehow drawing the “bad” insects away from the vegetables and letting them chew on its leaves. I was getting ready to hoe up all of the pigweed but I’ve had a change of heart. I’m going to let some of it grow. I’ll cut it back so it doesn’t get too big and I certainly won’t let it flower – each plant can produce tens of thousands of seeds and I don’t want those being added to the garden soil!

This year, I’m going to embrace this common weed and let it grow and attract the insects in the garden. I’ve never seen this happen before and I don’t know if it’ll happen again, but for now, it’s amazing. All I can say is that this year, my pigweed’s magic!

Weed du Jour – Common Pokeweed

If there’s one weed that I should have under control, it’s common pokeweed (Phytolacca americana). This large weed is easily controlled with cultivation if you don’t allow it to become established. But there are two places where I’ve found this perennial weed growing – the raspberry bed and the asparagus bed.

Young Pokeweed in Asparagus Bed

Young Pokeweed in Asparagus Bed

It’s not surprising that these are the two places where pokeweed has established itself. I try my best to keep these beds free from weeds but when the raspberries are tall and the asparagus has reached its 5′ height, I tend to miss some of them. Pokeweed is one I missed.

Pokeweed is a huge plant, growing from 3-10′ tall, that tends to grow in hedgerows, by fences, along the edges of fields and in other places where it can grow undisturbed, i.e. asparagus and raspberry beds! The plant is propagated by seeds that can remain viable in the ground for 40 years. The seeds spout in spring and early summer and grow quickly into large plants. But what you don’t see is that the plants are also growing a large taproot that can be 4″ wide and 12″ long. The leaves of pokeweed are either egg or lance shaped, often with a reddish tint on the underside as they mature.

Pokeweed Inflorescence

Pokeweed Inflorescence

In the summer pokeweed developes inflorescences that are long and covered with small white flowers. These flowers develop into berries that are a dark purple/black when mature. Each one of these berries has about 10 seeds inside of it. Pokeweed is spread by birds eating the berries and leaving the undamaged seeds in their droppings.

What sets pokeweed apart from most other weeds is that all parts of the plant are poisonous. The root is the most poisonous, the leaves and stems are intermediary (the level of toxin increases with maturity) and the berries have the least toxicity. However, there are reports of children being poisoned by the berries so, while less toxic, they’re still dangerous. The primary toxic compounds are phytolaccine, formic acid, tannin, and resin acid which cause gastrointestinal irritation but may also cause mutations and birth defects. Since these chemicals can be absorbed through the skin, it’s a good idea to not pull the plants with bare hands.

While this is a poisonous plant, in the South the young shoots are often eaten as a green that’s said to taste like either asparagus or spinach. There are also some who make pies or jelly from the berries. Personally, I would never eat this weed and am not recommending that anyone try it given its poisonous nature!

The other interesting thing about pokeweed is that it appears as an herbal remedy and is said to treat rheumatoid arthritis, tonsillitis, mumps, swollen glands, bronchitis and constipation. Once again, I’m not going to ingest this weed no matter what cures it promises to deliver.

Apart from the folklore about pokeweed, scientist have isolated one protein in it called pokeweed antiviral protein (PAP) which has shown anti-tumor effects on mice and antiviral effects on herpes and HIV in vitro and in animal studies. While this protein shows some possible medical uses, PAP is now made synthetically because the PAP extracted from pokeweed was often impure and contained the poisonous elements of this weed.

Common Pokeweed

Common Pokeweed

In the garden, pokeweed really isn’t a big problem unless you allow it to establish itself like I did. You can use a shovel and cut through the taproot of large plants to remove them; this will usually kill it. The one pokeweed I have right now is growing in the middle of an asparagus clump so I can’t dig it out. I figure I’ll keep pulling off new shoots as they develop. I also might cut the shoots and put a few drops of full-strength RoundUp into the hollow stems.

The best trick for controlling pokeweed is to keep up with the weed, pulling or cultivating it when you see it and not allowing the fruits to form. But given the fact that this weed grows all over the area, a few seeds will always end up in the garden and yard (thank you birds!). Pokeweed is something that’ll always be finding its way into the garden – I just need to keep a step ahead of it.

Weed du Jour – Scarlet Pimpernel

Scarlet Pimpernel

Scarlet Pimpernel

Yesterday I was doing some weeding in the garden. Whenever I weed I keep a close eye on what kind of weeds I’m removing. As I was working though a patch of yellow woodsorrel, I saw a weed that I’ve never seen before. It grew low to the ground and had the prettiest salmon/orange blossoms. I grabbed the weed, took it up to the house and got a few pictures of it before it wilted. While I wasn’t certain, I had a hunch that I’d discovered scarlet pimpernel growing in the vegetable garden.

While I’ve never seen this weed before, I’d seen pictures of it in the book Weeds of the Northeast. It’s name had caught my eye since I’ve seen the musical by the same name a number of times. Sure enough, when I checked, this new weed was easy to ID – scarlet pimpernel (Anagallis arvensis).

Note the Square Stems and Spots on the Underside of the Leaves

Note the Square Stems and Spots on the Underside of the Leaves

Scarlet pimpernel was introduced into the US from Europe and now grows throughout the states, particularly in the mid-Atlantic and the Pacific coast. This low growing annual has a shallow root system. The leaves are small (<1″), opposite one another and oval or triangular in shape. Any petiole that is present is very small. The underside of the leaves of scarlet pimpernel have small purple spots which help to identify this weed. The other identifying characteristic is the square stems of the plant.

Scarlet pimpernel has salmon to brick-red flowers (I know, they should be scarlet but I didn’t name this plant!) each with five petals that appear from June to August. The fertilized flowers produce a small fruit which contain 30-40 seeds each. A large plant can produce more that 12,000 seeds in one season – this is probably why it’s considered a weed.

Given its low profile and shallow root system, scarlet pimpernel isn’t a problem to control. Cultivation will easily limit this weed’s growth and if it’s growing in turf, any broadleaf herbicide should control it. Here in the Northeast, this weed isn’t very common. I’ve been gardening since the ’60’s and this is the first time I’ve ever seen scarlet pimpernel in the garden. It certainly isn’t a major concern.

While I will call scarlet pimpernel a weed, I have to say that this is a really pretty weed. I can understand why it was brought to the US from Europe. But despite its appeal, I’ll be pulling it up whenever I see it in the garden. Pretty or not, I don’t want it competing with the plants that I’m growing. I’m just glad to know what it is and to have finally spotted a scarlet pimpernel!

Weed du Jour – Yellow Woodsorrel

At this time of the year the weeds are growing very well. Between the warm weather, moist soil and a small vegetable and flower canopy, the weeds have perfect conditions in which to grow.

Yellow Woodsorrel - Note the Heart-Shaped Leaves

Yellow Woodsorrel – Note the Heart-Shaped Leaves

The one weed that I see the most in the garden is yellow woodsorrel (Oxalis stricta). The light green to reddish-green clover-like leaves and bright yellow flowers announce that woodsorrel has taken over parts of the garden.

While yellow woodsorrel can be a perennial in fields or turf, in the tilled garden it usually grows as a summer annual. The plants can range in height from a couple of inches to almost two feet depending on the conditions. Most of the woodsorrel I see is on the short side. This plant prefers moist, fertile soil so it’s right at home in the vegetable garden.

While this variety of Oxalis looks a lot like clover and black medic, the one thing that distinguishes it from these plants is its leaves. They consist of three leaflets, each of which is clearly heart-shaped.

Yellow Woodsorrel Immature Seed Capsules

Yellow Woodsorrel Immature Seed Capsules

Yellow woodsorrel can spread by rhizomes (underground stems) but its primary means of spreading is through its seeds. The plant bears small yellow flowers with 5 petals in the spring and early summer with intermittent blossoming during the rest of the growing season. When the flowers are fertilized, an elongated, upright seed capsule forms. When it’s mature, the seed capsule explosively breaks open and ejects the seeds up to 12′ away from the plant. No matter how diligent you are at weeding, it’s hard not to miss a few of these plants. And when you let some grow and their seed capsules mature, seeds are spread all over the garden. Because of this it’s no surprise that yellow woodsorrel can be a ubiquitous weed in the garden.

Woodsorrel can be a difficult to pull because of its rhizomes and it responds to most broadleaf herbicides. However, the main way to control this weed in the garden is through cultivation. The good news is that it’s not a very aggressive or competitive weed so it won’t crowd out other plants. But given the way that it spreads its seeds, every seed capsule that’s allowed to mature means that there’ll be more yellow woodsorrel growing next year.

I was a little surprised to see that an Illinois wild flower site lists yellow woodsorrel as a wild flower. I guess it just goes to show that one person’s wild flower is another’s weed. While I can appreciate the flowers of this plant, it’s a weed to me and one that I encounter every year.

Weed du Jour – Poison Ivy

Whenever I go out into fields or a wooded area, I’m always keeping an eye out for leaves with three leaflets. I don’t want to have any encounter with poison ivy.

IMG_0883

Poison Ivy in a Bed of English Ivy

Poison ivy (Rhus radicans) is a member of the Cashew family that’s native to North America. This perennial can grow as a vine along the ground, it can climb trees, shrubs and posts, reaching up to 100′ in the air and in full sun, it can take on a shrub-like characteristic. The most well know feature of this plant is that every leaf is made up of three leaflets, each about half as wide as they are long. These leaflets always have pointed tips but the edges may be wavy, smooth or with lobes. In addition the leaves grow from the stem in an alternating pattern. (This helps to distinguish poison ivy from the non-toxic box elder which has similar leaves with three leaflets but the leaves are in opposite pairs along the stem). Poison ivy is a dioecious plant, meaning that there are male plants and female plants. The male plant produces pollen which is spread by insects to the female flowers which produce berries.

Poison ivy is spread by birds that eat the berries and spread the seeds in their droppings. It also spreads by developing roots along its stem wherever it touches the soil.

Sometimes people confuse this weed with other “poison” plants, specifically poison oak and poison sumac. Here in Pennsylvania there is no poison oak – this plant grows to the south and west of the state. Poison sumac only grows in marshy areas so in most of the forests and fields of  PA, the only “poison” you’ll find is poison ivy.

What makes this weed so toxic is an oil that it produces called urushiol. The only parts of poison ivy plant that don’t have urushiol is the pollen and the inner wood of older stems. It isn’t only the leaves of poison ivy that can give you a rash; urushiol is also present in the stems, roots and sap of the plant. When urushiol makes contact with the skin, it binds to the outer layer and causes a rash in many people. It’s often said that washing after contact with poison ivy will prevent a rash from forming. Unfortunately, the urushiol binds almost immediately to the skin so washing quickly and very vigorously might limit the poison but is unlikely to remove all of it.

This oil is non-volatile but very stable. Because it’s non-volatile, the good news is that you can’t get poison ivy by being close to a plant; you have to touch it or come into direct contact with the urushiol. But since it’s so stable, the oil can be carried and remain active on garden tools, clothing and the fur of dogs and cats. Also it’s stability make burning poison ivy something that is warned against in every publication that I read. If you burn any part of a poison ivy plant, the urushiol becomes airborne and can settle on your skin and eyes and can even get into your lungs – yikes!

I was also shocked to see that one old wives’/woodsman’s tale is that to become immune to poison ivy you should eat a leaf of it. This won’t protect you from poison ivy but will pretty much guarantee a trip to either the ER or the morgue!

Since the reaction to the urushiol in poison ivy is an allergic reaction, just because you’ve never had it before doesn’t mean that your immune. Each exposure to poison ivy produces antibodies in the body so you can start getting poison ivy at any age after any number of exposures.

Fortunately poison ivy doesn’t generally grow in cultivated areas but it can be a problem in woodlots and undisturbed areas. If you have poison ivy growing on your property, getting rid of it is a difficult process. If you pull the plants – being sure to protect yourself from contact – any small pieces of root left in the soil will sprout and grow new plants. It’s said that mowing can control it but I wouldn’t touch poison ivy with a mower – think of the toxic clippings that would come flying out of it! There are herbicides that can control this weed but you have to remember that even if the plant is dead, the urushiol is still present in the dead tissue. If you have a poison ivy problem, I’d contact your local extension office to see what they’d recommend.

I think you can tell I really don’t like this weed. But the truth of the matter is that poison ivy does have some uses. It’s great for erosion control and the Dutch have actually planted it for this purpose. Some native Americans used it medicinally. Also a lot of animals eat poison ivy and others use it for protective cover. You see, we’re the only animal that’s affected by this weed!

After many encounters with poison ivy in my teens and twenties, I’ve gained a healthy respect for this weed. I’ve also developed a sixth sense that’s able to spot this weed before I come in contact with it. I’ve made that old adage my motto – leaves of three, let them be!

Roundup – What’s in that Bottle?

I’ve been a bit hesitant posting about Roundup, the non-selective herbicide. In some circles the word “Roundup” has become a shibboleth dividing the world into those who are environmentally conscious, opposed to big business and against genetically modified crops and those who aren’t. Personally, I’m somewhere in the middle on this whole debate. But in this post I just want to talk about what Roundup is, how it works and what’s in the bottles of Roundup lining the shelves of garden centers.

What got me thinking about Roundup was some of the commercials that I’d seen on TV for this product. One said that one kind of Roundup would kill weeds within a few hours. There’s also a commercial for a Roundup formulation that will continue to prevent weeds for up to three months.

Back when I was in college, Roundup was a fairly new and highly touted product. In a weed science class (yes, there are weed science classes!) we learned about how it worked and what it does. What I’d learned in that class was that Roundup doesn’t kill weeds instantly and it offers no extended control. So what’s up with those commercials that I’d seen?

The active ingredient in Roundup (at least it used to be) is glyphosate. This chemical is called a non-selective or broad spectrum herbicide because it doesn’t distinguish between different kinds of plants. Basically, if it’s green, glyphosate will kill it.

The way glyphosate works is interesting. When sprayed on a plant, the chemical is absorbed and tends to accumulate in the meristem of the plant. Meristem is a kind of tissue in plants that’s undifferentiated and can produce all kinds of different cells and tissue. You could call it the stem cells of a plant. The growing tip of a plant has apical meristem which produces leaves, stems and allows the plant to grow. Root meristem is located at the ends of roots and produces the various tissues that make up the root. Meristem is some of the most active tissue, constantly dividing and differentiating. While accumulating in the meristem, glyphosate also finds its way to the chloroplasts of the cells where photosynthesis happens.

When glyphosate is present in a plant, it attaches to an enzyme called 5-enolpyruvylshikimate-3-phospate or EPSP synthase. This enzyme is involved in a key step in the production of the amino acids phenylalanine, tyrosine and tryptophane. When glyphosate is attached to the EPSP synthase, the enzyme stops working and the plant can’t produce these three amino acids. Without them, the plant can’t make proteins containing these amino acids, the building of cell wall is disrupted, hormone production is interrupted and energy transport is stymied. While this biochemical disruption affects the whole plant, it’s especially harmful in the chloroplasts and the actively growing meristem.  The plant begins to starve and dies within a week or two.

The other thing about glyphosate is that it doesn’t remain effective outside of the plant for very long. The chemical binds to the soil and is broken down by microorganisms. You can notice this if you mix up some Roundup in a sprayer that isn’t clean. After a few days, it becomes less effective because the glyphosate binds to the dirt in the sprayer and can’t be absorbed by the plant.

I know this is a lot of technical information, but all of this was in my mind while seeing those Roundup commercials. Since glyphosate interrupts amino acid production, it can’t kill a weed in a few hours – it takes at least a week. And since it binds to soil, it’s not a long acting herbicide – it only affects the weeds that are sprayed with it.

Roundup-Weed-_-Grass-Killer-Super-Concentrate-stdSo this sent me on a search to the Scotts web site and I have to say that I was amazed. Back in the day, Roundup was glyphosate, period. But that’s not the case any longer. The fast acting Roundup has glyphosate but also diquat, a fast acting herbicide. Extended control Roundup also has glyphosate but added to it is Imazapic, an herbicide that prevent the germination of seeds. There’s also a Roundup for poison ivy that has glyphosate and Triclopyr, an herbicide for woody plants. If you’re looking for just glyphosate, you have to do some hunting; according to the site, only one Roundup product for use by homeowners (Roundup Super Concentrate) is just glyphosate.

Why are there all of these different formulations? I have my guesses! The only one that makes sense to me is the poison ivy product – woody weeds are hard to kill and the addition of a woody weed herbicide would likely make the product more effective. The others seem to me to be little more than attempts to appeal to suburban gardeners. People want weeds to die instantly; glyphosate takes a little time. So by adding diquat to the mix, people get faster, visible results. The extended control appeals to people who want to spray once and be done.

The other thing that has probably led to all of these formulations is that the patent on glyphosate expired in the year 2000. Now any company can use glyphosate; these various formulations help to keep Roundup competitive.

As I’ve said before, I’m OK with conscious and limited use of chemicals in the yard. But I like to know what I’m using and like to use the least possible. I find glyphosate works well for killing weeds in places were they can’t easily be controlled with cultivation. But I don’t want to use a mixture of chemicals if one will do the job. I don’t need instant results when I spray weeds. I also prefer to spray as needed and not use an extended control product that stays active in the soil for months.

Before I learned all of this, I thought Roundup was glyphosate. Now I know that’s not the case. I have some Roundup in the garage that has glyphosate and diquat – I’ll use what I have but from this point on, I’ll be reading the labels before I buy any more Roundup. I want to know what’s in the bottle before I use it.