A. Bashar - Weeds in Gardens

Short answer: dandelions keep coming back because the plant you pull or spray is only the top of the problem. The taproot usually sits 6 to 18 inches deep and a piece as short as 1 inch can grow a new plant, each plant can release up to 20,000 seeds that form without pollination, and those seeds land on every thin spot in the lawn. To get rid of dandelions for good, take out or kill the whole root (early autumn is the best time) and thicken the grass so new seedlings have nowhere to start. This guide explains how to identify a true dandelion, what the root and seed are doing underground and in the air, and which control methods actually reach the root. For a quick comparison with other yellow-flowered lawn weeds, see our guide to weeds with yellow flowers, and for more lawn weed profiles browse the Lawn Weeds section. Table of ContentsHow to identify a true dandelionWhy dandelions keep coming back: 5 reasonsHow to get rid of dandelions for goodHow to stop dandelions returningA note from the agronomist's sideWhere this appliesShould you keep some dandelions?Frequently asked questionsSources How to identify a true dandelion Common dandelion (Taraxacum officinale) is a perennial that grows from a flat rosette of leaves. UC IPM describes leaves 2 to 14 inches long with deep, irregular teeth that usually point back toward the centre of the plant (the name comes from the French dent de lion, "lion's tooth"). Older plants build a thick crown and a leaf mat 6 to 14 inches across. Photo: "Taraxacum officinale plant NC8" by Macleay Grass Man, CC BY 2.0. Four features separate a dandelion from its lookalikes: One flower head per stalk. Each yellow head is made of 100 to 300 small ray flowers and sits alone on top of its stalk. A leafless, hollow, unbranched stalk 6 to 24 inches tall that bleeds white, milky sap when snapped. Nearly hairless leaves with sharp, backward-pointing teeth. A single thick taproot that also oozes milky sap when cut. Photo: "Taraxacum officinale stem sap ST1" by Macleay Grass Man, CC BY 2.0. The University of Minnesota Extension lists three plants that are often confused with dandelion: common catsear, chicory and perennial sowthistle. It also notes that a second species, red-seeded dandelion (Taraxacum erythrospermum), grows in lawns and is managed the same way. Dandelion vs catsear (false dandelion) Catsear (Hypochaeris radicata) is the lookalike most people get wrong, because its flowers are almost identical. Run a finger over a leaf: catsear leaves are densely hairy with rounded lobes. Then look at the stalks: NC State Extension describes them as wiry, typically branched and leafless, so one catsear rosette often carries several heads, and it flowers mainly from mid-summer to early autumn. Chicory and sowthistle are easier to rule out, because both grow tall, leafy flowering stems, which a dandelion never does. Photo: "Hypochaeris radicata plant NC3" by Macleay Grass Man, CC BY 2.0. FeatureDandelionCatsearLeavesNearly smooth, sharp backward teethDensely hairy, rounded shallow lobesFlower stalkHollow, unbranched, one headWiry, usually branched, one to several headsMain floweringEarly spring, then on and off until autumnMid-summer into early autumnControlSame selective broadleaf herbicides; dig the taprootSame herbicides; dig below the crown Why dandelions keep coming back: 5 reasons Most people who ask why dandelions keep coming back have already pulled or sprayed them at least once. In nearly every case, one of the five reasons below explains the regrowth. 1. The dandelion root breaks and regrows The dandelion root is the main reason for the comeback. The University of Wisconsin gives a usual depth of 6 to 12 inches, and up to 3 feet in loose soil. When you pull a plant by its leaves, the root snaps a few inches down. Oregon State University Extension reports that taproot segments as short as 1 inch can regenerate a new plant, and the upper part of the root, the section you most often leave behind, is the most vigorous. Photo: "A better look at dandelion roots" by isforinsects, CC BY 2.0. That is why a lawn can look clean for two or three weeks after a weekend of pulling and then fill up again with rosettes in exactly the same places. 2. Every flower sets seed, even without bees The common dandelion in most lawns reproduces by apomixis: the seed forms from an unfertilised egg cell, so no pollination is needed and each seed is a genetic copy of its mother. A 2022 study in Nature Genetics identified the PARTHENOGENESIS gene that switches this on. For a lawn owner, the practical result is simple: every flower that opens becomes a seed head, and Wisconsin and Oregon State both put the output at up to 20,000 viable seeds per plant. Photo: "dandelion seed head | Pusteblume" by Oliver Liegmann, CC BY 2.0. 3. Seeds fly in from next door Each dandelion seed hangs under a parachute (pappus) of about 100 bristles. Researchers writing in Nature (Cummins et al., 2018) found that the parachute creates a stable ring of air above it and falls at about 39 cm per second in still air. Most seeds land within 2 metres, but in warm, dry, windy weather some travel much further, with one estimate of up to 20,000 seeds per hectare moving more than 1 km. Clearing your own lawn does not stop seed arriving from a verge, a vacant lot or a neighbour's yard. 4. Thin turf gives seedlings a place to start Rutgers Cooperative Extension puts it plainly: dandelions readily establish from seed in thin lawns. UC IPM notes that seeds germinate once the soil is at least 50°F (10°C) and fastest near 77°F (25°C), so bare patches can produce seedlings from spring through autumn. A dense lawn shades the soil surface and leaves little room; a lawn mowed too short, underfed or damaged by drought does the opposite. 5. The method or timing never reached the root Mowing has no effect on established plants, because the rosette sits below the mower blade (UC IPM). Vinegar, boiling water and other contact products burn the leaves but do not move into the root; Oregon State's weed guide rates organic herbicides only "somewhat effective" on dandelion for that reason. Spraying a selective herbicide in late spring, when the plant is pushing its energy up into flowers, also gives weaker root kill than an autumn treatment. Our test of whether vinegar kills weeds explains the leaf-burn problem in more detail. How to get rid of dandelions for good The right method depends on how many plants you have and where they grow. The table sums up what each option does to the root. MethodReaches the root?Best timingBest forHand digging with a long weederPartly; repeat on regrowthMoist soil, young plantsA few plants, organic lawnsSelective broadleaf herbicide (spot spray)Yes, moves to the rootEarly autumn; mid-spring second bestScattered to heavy infestations in lawnsNon-selective herbicide (glyphosate)Yes, but kills grass tooActive growthPaths, fence lines, beds before plantingVinegar, boiling water, flameNo, leaves onlyAny, but regrowth followsCracks in paving, short-term cosmetic killMulch at least 3 inches deepStops seedlings, not deep rootsAfter weeding a bedGarden bedsThicker turf (mowing height, feeding, overseeding)Prevents new plantsAutumn for cool-season lawnsEvery lawn, long term Dig out the dandelion root the right way Digging works well for a handful of plants if you remove enough root. Oregon State recommends cutting 4 to 5 inches below the soil surface with a knife or long, narrow weeding tool, and pulling when the soil is slightly moist and the plant is still young and small. Push the tool straight down beside the crown, lever it toward the plant, and lift slowly so the root slides out instead of snapping. Photo: "Radius weeder and dandelion" by John11b, CC0 1.0. Expect some plants to resprout from root left behind. Check the same spots after three to four weeks and dig again; each regrowth uses up more of the root's stored food. Fill the hole with soil and a pinch of grass seed so a new dandelion does not simply germinate in the gap. Selective herbicide: use it in early autumn For a lawn with more dandelions than you can dig, a selective broadleaf herbicide kills the weed without killing the grass. The University of Minnesota lists the common active ingredients as 2,4-D, MCPA, dicamba and triclopyr, usually sold as two- or three-way mixes. Late summer to early autumn is the best time, because the plant is moving sugars down into the root for winter and carries the herbicide with them. Purdue Turfgrass Science agrees, with mid-spring flowering as the second window. A few rules from Purdue and Rutgers make the difference between a good kill and a wasted spray: Let the spray dry on the leaves for at least 24 hours before rain or irrigation. Wait two to three days after spraying before you mow, so the product has time to move into the root. Avoid spraying when temperatures above 85°F (29°C) are forecast; most labels warn against it. Do not treat newly seeded grass. Wait until it has been mowed at least three times, usually 6 to 8 weeks after seeding (see our guide to killing weeds before overseeding). Leave the clippings on the lawn and do not use them as mulch around vegetables or flowers for 6 to 10 weeks, depending on the label. Our clippings guide covers when to bag instead. Spot-spray individual rosettes rather than blanket-spraying the whole lawn when the dandelions are scattered. It uses far less product and keeps clover and other plants you may want to keep. Dandelions in beds, paths and paving In garden beds, dig out established plants and then lay mulch at least 3 inches deep, which both UC IPM and Oregon State recommend to stop seedlings. Our guide on stopping weeds growing through mulch covers depth and edging. On gravel and in paving cracks, where there is no grass to protect, a non-selective product such as glyphosate works on the root; keep it off any plant you want to keep. Boiling water or a flame weeder will clear the leaves in cracks, but expect regrowth within weeks. How to stop dandelions returning Killing the plants you can see is half the job. Stopping dandelions from coming back depends on how thick and healthy the grass is. The University of Minnesota calls dense, healthy turf the best defence, and Purdue advises homeowners to raise the mowing height and fertilise on a regular programme rather than relying on herbicides alone. Mow higher. Taller grass shades the soil surface and leaves fewer gaps for seedlings. Feed the lawn. A thin, pale lawn is an open invitation; follow a fertiliser programme suited to your grass type. Overseed thin areas in the right season for your grass, and fill every hole left by digging. Remove flowers before they turn to puffballs. Mowing does not kill the plant, but the University of Minnesota notes that mowing before seeds mature reduces spread. A note from the agronomist's side Apomixis changes how you should think about a dandelion patch. Because the seeds are clones of their mother, one plant that seeds into a lawn can found a whole population of genetically identical plants, all with the same tolerance to your soil and mowing. That makes dandelions a symptom rather than the disease. On farms and research plots, the fastest way to make a weed problem worse is to keep killing the weed while leaving the gap in the crop canopy that let it in. Lawns work the same way: fix the density first, and the herbicide becomes an occasional tool instead of a yearly ritual. Where this applies The timings above ("early autumn", "mid-spring", late September to October in New Jersey) are for cool-season lawns in the temperate Northern Hemisphere. In the Southern Hemisphere, shift them by six months. Warm-season grasses such as St. Augustine, centipede and zoysia differ in herbicide tolerance, so check that the label lists your grass as safe before spraying. Herbicide products and active ingredients are registered country by country, and some regions restrict lawn herbicide use by homeowners; always follow your local label and rules. For how dandelions behave through the cold months, see do weeds die in winter. Should you keep some dandelions? Dandelions flower early, and bees do visit them. Oregon State's extension team describes them as "a snack, not a full meal" for bees, which do better on a variety of flowers, especially native plants. If you want to help pollinators, a mixed flower border does more than a dandelion lawn. Still, leaving a rough corner unsprayed costs little, and spot-treating only the lawn areas you care about keeps herbicide use low. Frequently asked questions Is it better to pull or spray dandelions? For a few plants, dig them with a long weeder and remove 4 to 5 inches of root, then check for regrowth. For a lawn with dozens of plants, a selective broadleaf herbicide in early autumn gives a more complete root kill with less work. Can a dandelion grow back from its root? Yes. UC IPM and Oregon State both report that a dandelion root section as short as 1 inch can produce a new plant, which is why snapped-off plants return. Does mowing spread dandelion seeds? Mowing over ripe puffballs scatters seeds, while mowing before the seed heads form reduces spread. Mowing never kills an established plant, because the rosette sits below the blade. Sources UC IPM (University of California), Pest Notes: Dandelions University of Minnesota Extension, Dandelions University of Wisconsin–Madison Horticulture, Dandelion, Taraxacum officinale Oregon State University Extension, Dandelions: Living with, or without, them (EM 9510) Oregon State University, Solve Pest Problems: Dandelion Purdue University Turfgrass Science, Dandelion Control NC State Extension Gardener Plant Toolbox, Hypochaeris radicata (catsear) Rutgers NJAES, FS385: Broadleaf Weed Control in Cool Season Lawns Cummins C. et al. (2018). A separated vortex ring underlies the flight of the dandelion. Nature 562, 414–418. Underwood C.J. et al. (2022). A PARTHENOGENESIS allele from apomictic dandelion can induce egg cell division without fertilization in lettuce. Nature Genetics 54, 84–93.