Kochia

What is kochia?

Kochia is a fast-growing summer annual in the goosefoot family. It came from Eurasia as an ornamental and now fills fields, roadsides and empty lots across the dry West and Great Plains. kochia identification starts with the hairs: seedlings are covered in fine white fuzz, and grown plants form a branched, pyramid-shaped bush of narrow, soft, gray-green leaves that redden as the season ends.

It is a serious weed because it does everything at scale. A single plant can drop tens of thousands of seeds, the dried plant tumbles across the landscape scattering them, and seedlings keep coming from late winter into midsummer. Kochia also cross-pollinates readily and develops herbicide resistance faster than most weeds; resistance to glyphosate, ALS-inhibitor herbicides, triazines and growth-regulator products such as dicamba has been documented. Relying on one spray rarely works for long.

Kochia identification: what to look for

Kochia is easiest to spot in two windows: as a woolly little seedling in spring, and as a dense, bushy, gray-green to reddish plant in mid to late summer. Run your fingers along a leaf; the soft hairs and the lack of a spine separate it from Russian thistle.

• Seedlings: Thick, dull green leaves with magenta undersides and long, soft white hairs. At the early button stage the whole seedling looks fuzzy.
• Leaves: Alternate, narrow to lance-shaped, smooth-edged and generally gray-green and hairy, from about 1/5 inch to nearly 2 1/2 inches long. Newer leaves lengthen as the plant matures.
• Stems and shape: Upright and heavily branched, usually from the base, with one central growing point, giving a broad pyramid shape. Stems often turn red late in the season.
• Flowers: Inconspicuous, green and petal-less, sitting in the angles of reduced leaves in spike-like clusters from July into fall.
• Fruit and seed: Small star-shaped fruits with knobby lobes or short horizontal wings, each holding a flat brown to beige seed about 1/16 inch long.
• Late season: Plants dry out, snap at the soil surface and roll as tumbleweeds. Dense mats of seedlings often come up the next spring where the old plant stood.

Where it grows in the United States

Kochia is common in crop fields, pastures and rangeland across the semiarid and arid parts of North America, especially the arid West and the Great Plains. In California it ranges from the Central Valley, Bay Area and coast to the Mojave and Sonoran deserts and the Great Basin, up to about 4,900 feet. It germinates in cold soil, as early as January in some areas, which gives it a head start over most summer weeds.

Look for it wherever soil has been disturbed and left open: tilled or fallow fields, newly planted crops, construction sites, gardens, ditch banks, road and railroad shoulders and old corrals. It also tolerates salt, and dense patches in a field can be a sign that soil salinity is rising.

Kochia look-alikes

A few plants get mixed up with it:

• Russian thistle (Salsola tragus): Another tumbleweed of the same habitats, but its leaves are narrower and scale-like with a sharp spine at the tip, and its stems are often striped red or purple. Kochia leaves are hairy and spineless.
• Fivehook bassia (Bassia hyssopifolia): Seedlings of the two cannot be told apart. Older fivehook bassia is hairier than kochia and branches along the main stem instead of from the base.
• Forage kochia (Bassia prostrata): A perennial relative that is valuable livestock feed. Make sure you are dealing with annual kochia before you remove or spray a stand.

How to get rid of kochia

Pulling, digging and mowing: Pull or hoe kochia while it is small; tillage and hoeing work best on plants under about 4 inches tall, and you will need several passes because seedlings keep emerging all summer. Mowing before or during flowering sharply cuts the seed left for next year (one study measured a 98 percent drop in seed density), but mowed plants regrow and can still set seed at typical mowing heights, so repeat it. Flame weeding works on seedlings under about 2 inches tall with soft stems; you only need to heat them until they change color, not burn them black. Once plants dry, collect tumbleweeds from fences and ditches before they shed seed.

Cultural control matters most, because the right conditions keep it from coming back.

• Keep ground covered and competitive. Kochia does poorly in well-managed perennial pasture, alfalfa or other dense plantings.
• In fields and large gardens, fall-sown cover crops or competitive crops such as winter wheat can suppress early spring kochia dramatically; spring-sown covers were not effective in trials.
• Skip unnecessary tillage, which can bring buried seed up and trigger fresh flushes.
• A few rows of stiff-stemmed corn or sorghum, or a fence, across the prevailing wind can catch rolling plants before they reach clean ground.
• Young kochia can be grazed, but watch livestock for nitrate and oxalate poisoning, especially in drought.

Herbicides: Treat kochia while it is young and before it flowers; options narrow fast as it matures. Avoid spraying at the woolly button stage, because the hairs keep herbicide from getting into the leaf. Integrated weed management guides list glyphosate and glufosinate for burndown of emerged plants before planting, preemergence options such as sulfentrazone, pyroxasulfone and metribuzin, and postemergence options such as dicamba, fluroxypyr, bromoxynil and mesotrione, but which ones still work depends on local resistance. University of Idaho reports kochia there resisting ALS inhibitors, glyphosate, dicamba, 2,4-D, triclopyr and aminopyralid. Rotate modes of action, combine spraying with mowing, tillage or competition, and when several products fit, choose the one least likely to leach into groundwater. Use only a product labeled for your exact site and follow the label; it is the law. If you hire someone to spray, make sure they hold your state’s pesticide applicator license; the rules for each state are in our pesticide applicator license guide.

Keeping it from coming back

Kochia seed is short-lived, usually lasting only a year or two in the soil, and very little survives three years. Most seedlings also can't come up from deeper than about 2 inches. Stop every plant from seeding for two or three seasons and the seed bank collapses quickly. Clean out fence lines and ditches every year, because that is where tumbleweeds pile up and drop seed.

Wash mud and seed off equipment after working in infested fields, keep disturbed ground covered with competitive plants, and scout early in spring. Kochia often goes unnoticed until it is big and much harder to kill, so early action matters.

Questions we get about kochia

Similar weeds

Russian Thistle (Tumbleweed)Salsola tragusAnnual SowthistleSonchus oleraceusBermuda ButtercupOxalis pes-caprae