HELPFUL HINTS HELPFUL HINTS
FROM THE LAWN INSTITUTE FROM THE LAWN INSTITUTE
WEED IDENTIFICATION 101
Tere are approximately 300,000 species of vascular plants that form the dominant vegetation covering the Earth’s surface. Vascular plants are defined by the presence of photosynthetic pigments and vascular tissues that carry water, minerals, and photosynthetic by-products throughout the plant. Within this group, flowering plants, also known as angiosperms, are a diverse group of land plants that are classified into 416 families. With this vast amount of plant species present, identifying weeds can often be quite tricky, so where is the best place to start?
Weeds, like all plants, are classified based on morphological characteristics of their reproductive and vegetative structures. Te most useful part of a weed for identification is the flower, but leaves, rhizomes, stolons, tubers, etc. also can provide important clues.
Weeds are often grouped into categories such as broadleaf weeds, grassy weeds, and sedges. Broadleaf weeds have variable leaf shapes and arrangements, netted leaf veins, and often colorful or showy flowers, but their flowers also can be small and inconspicuous. Grassy weeds have simple, entire leaves, parallel leaf veins, and most commonly small, perfect flowers that are arranged in spikes, racemes, or panicles. Sedges also have simple, entire leaves and parallel leaf veins which often lead them to be mistakenly called grasses, such as “nutgrass,” named after its underground tubers and grass-like leaves. Furthermore, there are several species of weeds with vegetative characteristics (leaves, stems, sheaths, etc.) that appear to be grasses, but when left un-mowed, their floral characteristics reveal that they are actually quite different. Tese species are sometimes referred to as “grass-like” weeds and can add another layer of difficulty to identification.
Identifying weeds based on morphological features is helpful because herbicides often are particularly effective on one or more of these groups. However, it is important to be able to identify specific weeds within a group (down to the genus and species level), because some herbicides may only control certain species. In addition to type of weed, the life cycle of the weed is important because it impacts when to treat it. Summer annual weeds are most easily controlled during spring prior to, or soon after germination, while winter annual weeds are best controlled prior to, or soon after fall germination. Perennial weeds, those with above or below-ground storage organs (rhizomes, stolons, tubers, bulbs, etc.), should be treated when they are actively growing and typically are more difficult to control.
Given the complexity of weed identification, it is often useful to seek the help of textbooks, websites, university or industry specialists, etc. to properly identify a weed before determining how to treat it. Tere are many useful resources available online, but it is important to consult reputable, industry or university websites that are regionally specific. Minor differences in species, regional common names, availability of registered herbicides, and more can have significant impacts on successful control.
Lastly, don’t forget the importance of healthy turfgrass as the first and best defense against weeds. Following proper turfgrass management practices can go a long way in reducing weed populations and stopping them before they become a problem.
For more information on lawn care and helpful “How to” tips, visit The Lawn Institute at:
www.TheLawnInstitute.org.
TPI Turf News September/October 2018 9
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