Lespedeza (common lespedeza or Japanese clover) is a persistent summer annual weed that infests turfgrass and lawns. This broadleaf plant forms dense, low-growing mats, choking out desirable grasses and leading to thin turf. Effective control relies on precise chemical application, as the plant becomes resilient to late-season treatments. This guide explains the life cycle and identification necessary to pinpoint the most vulnerable stages for treatment and achieve season-long control.
Identifying Lespedeza
Positive identification is the necessary first step, as lespedeza (Kummerowia striata) can be mistaken for clover or oxalis. Annual lespedeza is characterized by its prostrate, mat-forming growth habit, keeping it low to the ground and protected from mowing.
The leaves are trifoliate, appearing in sets of three small, oblong or wedge-shaped leaflets, similar to clover. These leaflets have distinct parallel veins running nearly perpendicular to the midvein. As the plant matures, its stems harden and develop a woody texture. Small pink or purple pea-like flowers appear in the leaf axils later in the season, signaling the beginning of seed production.
The Lespedeza Life Cycle
Lespedeza is a warm-season annual plant, completing its life cycle from germination to seed production within one season. Emergence is triggered when soil temperatures consistently reach a minimum of 70°F, typically occurring in late spring to early summer.
Once germinated, the seedling develops a deep taproot and begins its vegetative growth phase during mid-summer, forming dense, aggressive mats. The final stage is the reproductive phase, starting in late summer, where the plant produces flowers and sets seed. This stage coincides with the transition to a woody stem structure, which makes the mature plant far less susceptible to post-emergent herbicides. Preventing seed set is crucial because the seeds contribute heavily to the soil’s seed bank, guaranteeing reinfestation the following year.
Optimal Timing for Herbicide Application
Effective lespedeza management uses a two-pronged approach: pre-emergent and post-emergent applications. The pre-emergent strategy prevents germination and should be executed in early spring (March to early April). This application must occur before soil temperatures rise above 60°F, well before the 70°F threshold that triggers sprouting.
The most effective strategy is the post-emergent application, which targets actively growing seedlings. This is ideally timed for late spring to early summer, typically May through mid-July. During this period, the plants are young, tender, and have not yet developed their protective, woody stems. Spraying during this juvenile stage ensures maximum herbicide absorption and a high rate of control.
If treatment is delayed until late summer (August or September), the plant will have matured and become significantly less vulnerable. At this late stage, the goal shifts primarily to preventing seed drop for the following season, rather than achieving a quick kill of the established plant. Multiple post-emergent applications may be necessary to manage staggered germination throughout the summer.
Selecting the Right Herbicide and Application Techniques
Selecting an appropriate chemical product involves choosing active ingredients known to be effective against lespedeza.
Herbicide Selection
The most common choices are three-way broadleaf weed control products, which typically combine active ingredients such as 2,4-D, dicamba, and MCPP (mecoprop) or MCPA. These formulations provide systemic action, absorbed by the leaves and transported throughout the plant for a complete kill. For warm-season turfgrass varieties, specialized products containing metsulfuron-methyl or atrazine may be recommended.
Application Techniques
When applying post-emergent products, using a non-ionic surfactant is highly recommended, especially on mature plants. The surfactant helps the solution spread and stick to the waxy leaf surface, improving chemical uptake and efficacy.
The herbicide should be applied to achieve uniform coverage, ensuring leaves are fully wetted without excessive runoff. Avoid application during periods of extreme heat or drought stress, as this reduces herbicide absorption. Always wear appropriate personal protective equipment (PPE) and pay close attention to wind conditions to prevent chemical drift.