Why Is This Weed Here?
Sean Breckin, AOLCP

Spring has sprung, and soon, so will weeds. When scouting lawns and athletic fields for weeds it’s important to ask yourself: “WHY is this weed here?”. The short answer is always the underlying soil conditions. When evaluating areas, different weeds tell different stories regarding what’s going on with the soil. Below is a list of common weeds you will see in your lawn in the Spring and early summer.

Low pH

Clover is a rapid spreader. It thrives in soils with low pH, which is also an indicator of low fertility for turf grass. This Nitrogen fixing plant does indeed provide bioavailable nitrogen to turf grass through its ability to convert atmospheric Nitrogen (N2) into Nitrates (NO3-) and Nitrites (NO2-) and Ammonium (NH4+). However, it can be problematic for athletic fields because it compromises the integrity of the playing surface. While this pollinating plant may be just fine on a homeowner lawn, it doesn’t suit athletes playing sports. This is because it doesn’t allow for consistent ball rolling speed or areas for cleats to gain traction when changing direction.

Moist Soil

Chickweed is a winter annual that germinates early and is one of the first weeds to grow in the Spring. Chickweed has small white flowers and fleshy, egg-shaped leaves. It can dominate thin areas of lawn by forming dense mats. In addition, chickweed does particularly well in shaded areas. This plant performs particularly well in consistently moist soil. Thus, areas with poor soil structure or are highly compacted and thin can be an opportunistic site for chickweed. Be sure to aggressively seed thin areas to get turf grass into the area as quickly as possible (visit our blog “Beat Weeds With Grass Seed” for info on Spring seed varieties).

Poa Annua is a winter annual that thrives in moist soil conditions. It is particularly noticeable in part shade conditions, but can persist throughout lawns due to its low growth habit and ability to seed prolifically. Its green coloring is vibrant and easily distinguishable from desirable turf grass species. Like most Spring weeds, it dies off as the heat of summer onsets and you’re left with large dead areas of lawn. These areas are extremely unsightly and are not optimal for visual standard or field usage.  Be mindful of mowing practices – this moist grassy weed can store seeds in your mower deck and spread throughout your lawn. Therefore, do your best to bag clippings when this weed is in seed. Another critical component is overwatering with irrigation, always do deep infrequent watering and be conscious of PJC’S recommended 1-2-3-2-1 Watering Method.

Compacted Soil

Plantain is a telltale sign of compaction. This plant has strong taproots that can ‘break’ poorly structured soils and steal calcium. Turf grass roots don’t have the moxie to break compacted soils and require assistance through aeration and overseeding and gypsum to provide bioavailable calcium and improve soil structure. It tolerates a wide range of moisture conditions, making it extremely difficult to manage. This is especially relevant on athletic fields where foot traffic from athletes is so high. Plantain will start to show significant formation late Spring and early summer.

Dandelions are probably the most easily identifiable weed. Dandelions tolerate a wide range of soil conditions, but do especially well in compacted soils as their large taproot is able to ‘break’ soils and steal calcium. This plant first grows in early Spring and can flower all the way through the season. Similarly to plantain, dandelion is most noticeable in soils where calcium isn’t abundantly available for turf grass, which can be soils low in pH or highly compacted soils. More often than not, a lawn or field that has an abundance of dandelions will require calcitic lime to address the underlying soil issues of low calcium availability and low pH.

Practical Approach

No matter which weeds you find when scouting in the Spring, the key is to grow more turf. Through fertility and cultural practices you can create a lush stand of turf to crowd out weeds. Start with these cultural practices this Spring:

  1. A high height of cut shades out prostrate growing weeds and limits weed seeds from getting to the soil surface. 
  2. Deep watering encourages turf root growth and limits shallow, moist soils that certain weeds thrive in. 
  3. Keeping pH in range through liming is essential for nutrient availability and soil structure. 
  4. Turf species diversity is also critical to enhancing competition on athletic fields and lawns – in Spring Rye grass is going to be most prevalent, in early Summer – tall fescues and Kentucky blue will be most competitive. Over the heat of summer tall fescue does a great job of remaining competitive with summer, then in late summer and fall, Kentucky blue and rye will dominate again. Maintain high species diversity and keep cultural practices as your highest priority to compete against weeds.

Again, when identifying weeds, ask yourself “Why is this weed here?” and follow up with “Am I growing the best turf grass I can be?” If the answer is “No”, reach out to PJC for info about our organic turf products and Support Services.