Spotted Spurge: The Weed Nobody Knows

Standard

Spotted spurge (Euphorbia maculata). Photo: plantsam.com

In my area, this has been a banner year for spotted spurge (Euphorbia maculata, formerly known as Chamaesyce maculata), also called spotted euphorbia, spotted sandmat and milk purslane, a low-growing, spreading annual weed most often seen in thin lawns, along roadsides, growing from cracks in sidewalks and in waste ground and elsewhere in sunny spots of disturbed soil. 

We’ve had a very hot, dry summer, something lawn grasses detest, and that allowed spotted spurge, normally a fairly discreet weed in my area, to take over, even covering vast stretches of burnt-out lawn. As a result, I’ve been receiving photo after photo of this plant, asking what it is. Although very adaptable, it does seem to do especially well in poor, compacted soil in full sun. Where it thrives, it outcompetes other plants, like lawn grasses.

Spotted spurge can make an attractive, if temporary, groundcover. Photo: plants.ces.ncsu.edu

Spotted spurge is actually quite attractive, making a nice, thick carpet, with creeping stems radiating outwards from a deep taproot up to 2 feet (60 cm) long, leading to some people to wonder if it couldn’t be used as a groundcover or even a lawn substitute. However, its annual nature, that is, dying in the fall and sprouting anew in mid-spring from seeds left in the ground, means it would only successfully cover ground after it has filled in, from midsummer to late fall. In spring and early summer, it would still be too small to make an effective groundcover … and what use is a groundcover that leaves the ground uncovered for 6 or more months of the year?

Close-up showing the leaves, tiny flowers and seed capsules. Photo: http://www.inaturalist.org

The paired leaves, lanceolate oval in shape, about 1/6 to 2/3 of an inch (4–17 mm) and with barely any petiole, are mid-green, usually smooth with a reddish margin and an elongated purple spot in the center. They’re borne on pink to maroon somewhat hairy stems that don’t root at the nodes. The purple spot that gives the plant its name is not always present and, if not, this plant could be confused with other closely related ground-hugging spurges like prostrate spurge (E. prostrata), sprawling spurge (E. humifusa), ridge-seed spurge (E. glyptosperma) and matted sandmat (E. serpens), all are best told apart by their broader leaves. Also, spotted spurge is much more widespread than its relatives.

As for the flowers, they are tiny and insignificant, pink fading to white, and growing in clusters at the leaf axils. Get out your magnifying glass if you want to study them! 

Spotted spurge usually grows perfectly prostrate. Photo: aggie-horticulture.tamu.edu

Spotted spurge usually remains very low-growing (under 1 inch/2.5 cm), so can’t be controlled by mowing, but can reach 4 inches (10 cm) if surrounded by competing plants. It usually spreads to about 18 inches (45 cm) in diameter.

The milky white sap helps identify spotted spurge. Photo: thegreenthumb20.wordpress.com

To distinguish spotted spurge from other small-leaved creeping weeds like knotweed (Polygonum aviculare) or purslane (Portulaca oleracea), just break off a piece of stem. Only the spurge produces white latex from its wounds. As with most euphorbias, the latex is irritating to the skin and poisonous if igested. Some people have fairly serious allergic reactions to the sap, so if you’re doing any hand-pulling, wear gloves.

The tiny flowers produce even tinier brown seeds. Plants only five weeks old already produce viable seed and produce them continuously until the the death of the plants in the fall. Each plant produces thousands of seeds per year and they can remain dormant for years until appropriate conditions appear. They readily stick to shoes and animal fur and can thus be transported over great distances.

Distribution of spotted spurge in North America north of Mexico. Photo: USDA

As a result, this plant, originally thought to be native to the American Midwest, has spread throughout that country and north into Canada and is now found, although sometimes in a still localized fashion, on all continents except Antarctica.

How to Control Spotted Spurge

Knowing what the spotted spurge wants can help guide you in controlling it. 

It needs light to germinate, so won’t germinate under mulch nor in a thick lawn. In flower beds and vegetable gardens, just keeping the plants well mulched is therefore all the control you’ll likely need.

As for lawns, anything that will help yours grow better (appropriate watering, fertilizing, mowing, etc.) will hinder spotted spurge.

Spotted spurge has completely overtaken this drought-weakened lawn. Photo: Jocelyne Gilbert

If your lawn is thin, which would allow spotted spurge seeds to germinate, consider topdressing with 3/4 to 1 inch (2 to 2.5 cm) of quality topsoil (spurge seeds won’t germinate if covered with more than 1/2 inch of soi), then overseeding with quality grass seed or clover. This will help thicken the lawn and make it unattractive to spotted spurge (and indeed, to most lawn weeds). Early fall is the best time to topdress and overseed.

Hand pulling is one way of removing spotted spurge from paving stones. Photo: Harry Rose, Flickr

Hand-pull plants wearing gloves, taking care not to get the sticky sap in your eyes. Weeding a day after a thorough rain or watering will make the plant easier to pull out. You need to extract at least the top part of the root; otherwise it will grow back from the base. Hand weeding, obviously, will be most effective when carried out early in the season, when the plants are small with still-shallow roots, before they start producing seeds.

Avoid purchasing nursery plants with spotted spurge growing in the pot.

Preemergent herbicides like corn gluten meal can be effective, but only if applied just before the seeds germinate (they start to do so at when the soil reaches about 60 ° F [16 ° C]). Carefully follow instructions: these products will have no effect if not applied properly. 

Lawn care companies may still be allowed to spray certain lawn herbicides on home lawns. Photo: http://www.solutionsstores.com

In most areas, lawn herbicides designed to kill broadleaf weeds but not lawn grasses are no longer available to home gardeners, but lawn care companies may still have access to a few of them and most will control spotted spurge.

Spot herbicide treatments with non-selective herbicides, ones that kill a wide range of plants, will usually be effective when applied to spotted spurge and are useful in controlling it in patios and sidewalks. They can be used in lawns as well, but since they also kill most lawn plants, must be used with great care. 

__________

Spotted spurge: a mystery weed no more!

7 thoughts on “Spotted Spurge: The Weed Nobody Knows

  1. I have this growing in my garden (not on purpose lol) and it covers the sides of my butternut squash hills. Keeps the moisture in really well and hasn’t caused excessive moisture that leads to blight and other moldy stuff. I make sure though to pluck it from right underneath the plants , and leave it on the sides of the raised row. It also keeps other weeds from popping up. I’m honestly considering using it as weed control and to keep moisture in lol for the sides of the hills and walking rows!

  2. Goodness! I never considered exploiting it as a ground cover. I dislike it so much that I always try to get rid of it. It is not a majore problem where I live and work now, but is one of the main weeds where I used to live in town just a few miles away. (The climates and soils are very different.)

  3. Joe

    I wasn’t aware of the name of this plant before reading this, but am struck by the enlarged photo: the leaves have a slight resemblance to Persicaria maculosa (syn. Polygonum persicaria) commonly known as lady’s thumbprint or smartweed. Also, I learned that a culinary herb I have used for some years in stir fries or other Asian dishes, Persicaria odorata, or Vietnamese coriander, is related to Persicaria maculosa, and in fact my potted coriander plant has sent up 2 flower stalks this year. They look just like Persicaria maculosa flowers. My hmong neighbors tell me they use it in cooking, but they couldn’t tell me what it was called in their language, just that it was a garnish type of ingredient. It’s been a season of learning, in many ways!

  4. This weed is always present in my community garden. Earlier this year, I had a first-time nasty allergic reaction (on my hands and one eye, probably due to brushing the hair back frim my face, or wiping away sweat) after pulling weeds and harvesting vegetables in the blazing heat. Spotted spurge is one of the weeds I was pulling (sticky sap and all), along with purslane, lambs quarters, baby maples and so forth. Between the different weeds and the scratchy stalks of my courgettes, I just could not figure out which plant I reacted to. From your description, it seems like the spotted spurge might be the culprit.
    I’ve put down some BRF mulch, which is suppressing most weeds, and I’ve been wearing gloves any time I garden — not ideal for harvesting baby green beans! But if it’s most likely the spurge, maybe I can moderate the glove-wearing a bit.

Leave a Reply to Laidback Gardener Cancel reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Google photo

You are commenting using your Google account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

This site uses Akismet to reduce spam. Learn how your comment data is processed.