Bull paspalum (Paspalum boscianum), or thin paspalum, is a persistent perennial grassy weed. It spreads rapidly in lawns and landscaped areas, forming thick, challenging clumps.
Identifying Bull Paspalum
Bull paspalum has distinct characteristics: flat leaves with wavy edges, a prominent mid-vein, and sparse hairs near the ligule (short, membranous, fringed). Young leaves may be purple.
Stems grow in bunching clumps. Sheaths are smooth, loose, with a continuous collar. During warmer months, it flowers, producing small, white, spike-shaped seed heads, usually with three to seven per stem.
Its fibrous root system spreads via short rhizomes and seeds. Distinguishing it from similar weeds like dallisgrass or crabgrass is challenging; young bull paspalum leaves are glossier.
Why Bull Paspalum Poses a Challenge
Bull paspalum is challenging due to aggressive growth. It spreads rapidly, forming dense clumps that outcompete desired plants, dominating areas and impacting health.
The weed has deep roots and rhizomes, making removal difficult. Small rhizome pieces can regenerate, recolonizing disturbed areas. It also produces many viable seeds, spreading by wind, human activity, or animals.
Bull paspalum adapts to diverse soil and environmental conditions. It thrives in humid, warm climates and sandy soils, often found in disturbed areas, dry sites, and lawns. Tolerant of flooding and drought, it persists. Its low growth allows it to tolerate mowing.
Control and Management of Bull Paspalum
Cultural Practices
Promoting a healthy, dense lawn is a primary defense. Maintain turfgrass at 3 to 3.5 inches; taller grass shades soil and reduces weed seed germination. Remove no more than one-third of the blade at each mowing to maintain turf health.
Adequate watering encourages deeper root growth in desirable grasses, making them resilient. Most turfgrasses require 1 to 1.5 inches of water per week, applied deeply and infrequently. Water in the early morning to reduce evaporation and allow foliage to dry, minimizing fungal issues.
Proper fertilization provides essential nutrients for turfgrass vigor, helping it outcompete weeds. Nitrogen is important for shoot and root growth; a soil test determines nutrient needs. Aeration improves soil health by alleviating compaction, allowing air, water, and nutrients to reach grass roots, fostering stronger turf.
Manual Removal
Manual removal is effective for small infestations. Hand-pulling requires removing the entire root system and associated rhizomes. Bull paspalum has a tough, central crown, difficult to pull when mature.
Digging out clumps with a shovel ensures thorough removal of rhizomes and roots. Even a small rhizome piece can lead to new growth, so complete removal is necessary. Dispose of removed weeds in a garbage bin, not compost, to prevent spreading seeds or fragments.
Chemical Control
Chemical control offers a solution for widespread bull paspalum. Herbicides are categorized as pre-emergent or post-emergent. Pre-emergent herbicides are applied before weed seeds germinate, creating a soil barrier that prevents development. They are not effective against existing weeds but reduce new growth.
Post-emergent herbicides control actively growing weeds. MSMA and DSMA can eradicate paspalum without harming some grasses, depending on turf type. Glyphosate is a non-selective herbicide that kills any plant it contacts, so apply carefully via spot spraying or painting to avoid desirable plants. Selective herbicides (e.g., metsulfuron, halosulfuron, sulfosulfuron) control paspalum without damaging certain turfgrasses like zoysia or couch grass, but are often unsuitable for buffalo or kikuyu lawns.
Timing is important; herbicides are most effective when bull paspalum is actively growing. Always read and follow product labels for instructions, application rates, and safety precautions. Wear protective gear (long pants, shirts, chemical-resistant gloves, eye protection, mask) during application. Avoid applying herbicides on windy days to prevent drift, and ensure suitable temperature.
Prevention Strategies
Preventing bull paspalum establishment is a long-term strategy. Apply a 2 to 3-inch layer of mulch to suppress annual weeds by blocking sunlight. Bark or chipped wood mulches are effective, and some contain pre-emergent herbicides.
Monitor vigilantly for new bull paspalum, allowing early intervention and easier removal before establishment. Proper seeding practices, like choosing adapted turfgrass species and ensuring dense turf, prevent weed encroachment by reducing open areas. Regularly clean gardening tools and equipment to prevent accidental spread of seeds or rhizome fragments.