Lawn weeds are flat-out the biggest pest problem in gardens and yards.
Some simply wreck the uniform appearance of a lawn, others are
poisonous, a nuisance or noxious. A few are edible or even produce
beautiful wildflowers and might not be deemed a weed by your neighbor.
Weeds growing in your landscape cause problems because they steal light, water, nutrients and space from your valued plants. They also look ugly and messy.
A weed can be defined as "a valueless plant growing wild, especially one that grows on cultivated ground to the exclusion or injury of the desired crop."
Not everyone considers them a weed...
Dandelions, yellow wood sorrel, purslane, chickweed are examples of edible plants you can find around your property. Did you know these 'weeds' are used by many in salads, soups or as seasonings? If you are growing these plants in an edible landscape, be a good neighbor and don't let them go to seed ;)
White clover used to be a standard addition to grass seed blends; today many consider it a lawn weed. As a legume, clover has the ability to capture nitrogen from the atmosphere and convert it into a form usable to plants. When mixed with grass seed it serves as a nurse plant, protecting the grass seedlings and supplying them with nitrogen.
Some weeds are actually attractive wild flowers when not growing
in a manicured lawn. Thistles are nasty and noxious weeds but - in my
humble opinion - have beautiful flowers. Take a close look at
chickweed, henbit or clover flowers - these pesky plants actually have pretty little flowers and are often used in wildlife plantings and butterfly gardens.
Weeds have survival skills that are the envy of the plant kingdom. They are very good at reproducing and often thrive is harsh conditions. Sprouting mainly by seed, these invaders will also spread by underground roots and shoots that generate new plants.
Lawn weeds are prolific seeders. Did you know a single common purslane plant is capable of producing over 50,000 seeds in one growing season? That's a lot of seeds!
Many weed seeds remain viable in the soil several years, waiting for the right environmental conditions. They will sprout when given contact with soil, sunlight, and moisture. Weeds produce plenty of seeds and they usually have a clever method of spreading them. Remember picking dandelion puffballs and blowing the seeds? Kids love that...and the winds will carry those seeds miles.
Perennial weeds can be trouble for gardeners in lawns and
landscape beds because they reproduce by seeds and vegetative plant
parts. Many will start by sprouting from a seed and then spreading by
underground roots (call rhizomes), surface roots (stolons) or spreading
stems that sprout new plants. These creeping, spreading roots and stems
will quickly colonize large patches of your lawn and landscape beds.
Why is it important to understand weed types and their life cycle? To plan the best and most effective weed control strategy.
When is the best time to kill weeds? Whether using a hoe, hand weeding tool or herbicide...the best time to attack a weed is when it is a seedling and has just started to grow - that is when it is most vulnerable.
The next best time to kill weeds is when they are actively growing. When weeds are in flower or seed stage, they are not actively growing.
Lawn weeds are generally divided into groups based on their physical characteristics and when they grow. They are either grasses or broadleaf plants and then further divided into annual, perennial or biennial plants based on life cycle.
Oxalis, crabgrass and common chickweed are examples of annual weeds. Annuals complete their life cycle within one growing season. Zap them with your lawn weed killer when they are young and actively growing. Herbicides are not very effective when annuals are flowering or produce seeds.
Crabgrass is a grassy annual weed and an effective way to control grassy weeds is to preventing their seeds from germinating by applying a pre-emergence herbicide.
Biennials take two years to complete their life cycle. The first growing season is called the rosette stage. They complete their life cycle in the second year as their stems expand - this is called bolting - and then they flower and seed completing their life cycle. Bull thistle is an example of a biennial weed. The best time to control biennial plants with an herbicide is when they are in the rosette stage.
Perennials live two or more years. Dandelions, broadleaf plantain, ground ivy and common bermuda grass are perennial lawn weeds. These weeds need to have their roots and shoots killed with an herbicide that moves through the whole plant. The most efficient time to use an herbicide is in the fall when the sugars are moving into the root system.
Perennial grass weeds are difficult to control. Large patches will usually need to be sprayed with a non-selective herbicide containing glyphosate (Roundup is the most popular brand) and then the lawn will need to be reseeded.
Yellow and purple nutsedge are perennial grass-like weeds
but they are not grasses. They form little bulblets and thousands of
seeds and are often referred to as 'nutgrass'. Nutsedges are very
tolerant of close mowing and tend to be a problem in wet areas.
Our Weed Identification Guide includes pictures, descriptions and control options of several common weeds and it is being constantly updated.
Noxious weeds are especially harmful or invasive and difficult to control. These weeds are designated by law as noxious and are usually required to be killed or removed. Canada thistle and Johnsongrass are examples of lawn weeds that are listed as noxious.