Weedy annuals include 3 life-cycle types here in Arizona.
Annuals germinate in fall and die in early spring.
Summer annuals germinate in early spring and die in fall with the first frosts.
Biennials live for 2 years, but may produce seeds during both growing seasons.
Each weed species requires a different eradication strategy, weather and time of year also factors into weed control. By knowing the life cycles of common weeds, control will be easier in the future.
Redstem Flaree (Erodium cicutarium) was introduced from Europe native to Mediterranean region. Annual or winter annual, reproduces by seeds. Overwinters as rosette and blossoms in early spring. Flowers April to June and is one of earliest flowering plants in spring.Widespread across North America, abundant on Pacific Coast. A weed in fields and waste places, sometimes lawns, pastures, and on dry soil.
Russian thistle (Salsola tragus ) was introduced from Russia and is an annual which reproduces by seed. It is a bushy, much-branched plant growing 1 to 3-1/2 feet high. The branches are slender, succulent when young, and woody when mature. Russian thistle grows on dry plains, in cultivated fields, roadsides, and waste places, chiefly in grain-growing areas. At maturity, the plant breaks off at the base and because of its round shape becomes an excellent tumbleweed.
Sow Thistle, (Sonchus oleraceus) a native to Europe, is a tall, course annual with milky juice. Sow Thistle is found in cultivated fields, meadows, roadsides and waste places. A perennial reproducing by seed and underground roots. The stems are hollow, smooth and branching at the top. The flower is yellow, dandelion-like.
Annual Bluegrass, (Poa annua L.) a turf grass weed that grows best in cool, moist conditions and rich soil but tolerates a variety of conditions including compacted soils. This weed lives as an annual and perennial. Reproduction by seed and favors golf greens and cool, moist conditions. Annual bluegrass can be controlled with pre- and post-emergence herbicides.
London rocket (Sisymbrium irio L.) is a European native weed belonging to the mustard family,and is one of the first winter weeds to appear in southern Arizona. It is abundant in irrigated land in crops such as alfalfa and small grains, in gardens, citrus orchards, pastures, and along roadsides. London rocket is a bright green fleshy winter annual. The stems branch from the base 1 to 3 feet high. It has a coarse taproot. Small, yellow flowers are borne on slender stalks in small clusters at the stem tip.