The painful, spiky objects sometimes found embedded in turfgrass are the protective seed capsules produced by common lawn weeds. These structures, often called “stickers” or “burrs,” are the result of the plant’s reproductive cycle and are designed to attach to animals or people for dispersal. The weeds that create these sharp seed pods are highly successful invaders that thrive in thin, stressed turf. Understanding that the sticker is a mature seed allows for more effective identification and timing of control strategies.
Identifying the Spiky Invaders
The most common culprits responsible for painful lawn burrs fall into three main categories of weeds, each with distinct physical characteristics.
Lawn Burweed (Spurweed)
One of the most widespread is Lawn Burweed, or Spurweed (Soliva sessilis), a low-growing, broadleaf plant that forms small, flat rosettes close to the soil surface. This winter annual is easily recognized by its finely divided, parsley-like leaves and the tiny, sharp burrs that develop in the center of the leaf axils. The burrs are small, usually less than a quarter-inch, but they contain sharp, rigid spines that cause discomfort when stepped on barefoot.
Sandbur
Another major offender is the Sandbur, which belongs to the Cenchrus genus and is a grassy weed, unlike the broadleaf burweed. Sandbur plants are annual grasses that grow in dense clumps, with leaf blades up to half an inch wide. The mature burrs are larger and more complex than those of the burweed, typically measuring 4 to 10 millimeters long and covered in numerous sharp, barbed spines. These spiky seed heads detach easily from the parent plant and readily cling to clothing, pet fur, or skin.
Puncturevine (Goathead)
In areas with sandy or disturbed soil, the Puncturevine, or Goathead (Tribulus terrestris), presents a hazard with its formidable, woody burrs. This plant grows in a prostrate, mat-forming habit, with stems radiating out from a central taproot. Its fruit is a hardened capsule that splits into five wedge-shaped segments, each equipped with two or more stout, pointed spines that resemble tacks. While often found in non-turf areas like roadsides and gravel lots, Puncturevine burrs are exceptionally durable and can cause severe puncture wounds to feet or bicycle tires.
Understanding the Sticker Lifecycle
The appearance of the painful sticker structures marks the final stage of the weed’s reproductive cycle, signaling that the plant has successfully set seed. The timing of this seed production is directly related to the weed’s life cycle as either a winter annual or a summer annual.
Winter Annuals (Lawn Burweed)
Lawn Burweed is a winter annual, meaning its seeds germinate in the cool temperatures of the fall and spend the winter growing as small, inconspicuous rosettes. The plant flowers and produces its distinctive burrs in the late winter and early spring. By the time the weather becomes warm in late spring or early summer, the entire plant dies, leaving behind only the sharp seed capsules. This timing is crucial because once the spines have fully hardened, control efforts must focus on managing the physical burrs rather than the living weed.
Summer Annuals (Sandbur and Puncturevine)
In contrast, Sandbur and Puncturevine are summer annuals, germinating later in the spring and growing vigorously throughout the hot months. These summer annuals produce their spiky seed heads later in the year, typically from mid-summer into the fall. The burrs are shed from the plant as they mature, ensuring a fresh supply of viable seeds is ready to germinate the following spring. For both types of weeds, the appearance of the burr means the opportunity for easy chemical control of the existing plant has passed.
Eradication and Prevention Methods
Effective control of sticker-producing weeds requires a strategic, multi-faceted approach that targets the plant before it can produce its mature, painful seeds. The most reliable method involves the timely application of pre-emergent herbicides, which work by creating a chemical barrier in the soil that prevents seeds from successfully germinating.
Pre-Emergent Timing
For the winter annual Lawn Burweed, pre-emergent products containing active ingredients like prodiamine or dithiopyr must be applied in the late summer or early fall, typically around September or October. This timing intercepts the germination of the weed’s seeds as soil temperatures begin to drop. For the summer annual Sandbur, the pre-emergent application should be timed for the early spring, usually in April, before the soil warms enough for the seeds to sprout. A split application, applied once in early spring and again six to eight weeks later, can provide extended control throughout the summer growing season.
Post-Emergent Control
If pre-emergent control is missed, post-emergent herbicides must be used while the weeds are still young and actively growing, and critically, before the burrs form. For Lawn Burweed, this means applying a broadleaf herbicide in the winter months, such as January through March. Effective post-emergent treatments often include three-way herbicide formulations containing a blend of active ingredients like 2,4-D, dicamba, and mecoprop (MCPP).
For Sandbur, post-emergent control is more challenging once the grass-like weed is mature, but the herbicide quinclorac can provide some results, particularly when the Sandbur is in its seedling stage. When applying any post-emergent chemical, it is important to read the label carefully to ensure the product is safe for the specific type of turfgrass in the lawn. Always add a non-ionic surfactant to many post-emergent applications, as this helps the herbicide adhere to the weed’s waxy leaves, increasing absorption.
Cultural Practices and Mechanical Removal
Beyond chemical intervention, cultural practices are a powerful long-term preventative measure, as these weeds thrive in thin, stressed turf. Cultivating a dense, healthy lawn naturally crowds out low-growing, opportunistic weeds like Lawn Burweed and Sandbur. This involves maintaining the proper mowing height for the grass species, which encourages a thick canopy that shades the soil and inhibits weed seed germination. Correct fertilization and watering practices also contribute to turf density, which serves as a biological barrier against invasion.
Mechanical control, such as hand-pulling, is a viable option for small infestations but must be done before the burrs mature and drop to the ground. For larger areas, a lawn vacuum or a thorough raking can physically remove the mature, detached burrs, preventing them from propagating further. Any clippings or removed weeds with burrs should be bagged and disposed of, rather than composted, to ensure the seeds are not spread back into the lawn environment.