Iva xanthiifolia

Scientific Name	Iva xanthiifolia Nutt.
Synonyms	Cyclachaena xanthiifolia (Nuttall) Fresenius
Common Names	English: False ragweed, burweed marsh-elder, careless-weed, German: Schlagkraut; French: Ive à feuilles de lampourde
Description	Tall robust annual, 0,6-1,8 m (1.97 - 5.9 ft) high, producing a taproot. I. xanthiifolia is native to North America.

Characteristic Features

Relatively long furrows (10 µm, 0.00039 inch).

Young Plant

Long cotyledons and mostly opposite young leaves.

Stems

Moderately branched, grayish-green, smooth, up to 1-2 m (3.28 - 6.56 ft).

Leaves

Leaves broad, mostly opposite, later alternate, light grayish-green, lower surface covered with small silky, soft hairs, with toothed margins, 5-20 cm (1.97 - 7.87 inch) long and 3-15 cm (1.18 - 5.9 inch) wide; ovate to broadly ovate, margins coarsely serrate to lobed, often double serrate.

Flowers

Flower heads small, drooping, borne in panicles at top of stem and in axils of upper leaves. Flowers either male (inner staminate) or female (outer pistillate) but borne in the same head, without petals, white-greenish-yellow in color.

Flowering Period

July-October.

Fruit

Achene.

Seeds

Gray to black, triangular, somewhat flattened with a ridged surface, about 3 mm (0.118 inch) long, produced in abundance.
Germination in spring.

Viability Of Seeds

Long viability in the soil.

Propagation

By seeds.

Habitat

Abandoned fields, bottomlands, flood plains, stream banks.

Soil

Moist rich soils.

Agricultural Importance

I. xanthifolia is a major weed problem in Texas pastures. The species is very prolific and can be difficult to control if not controlled early. It can reduce forage, hay quality and yield. Similar to ragweed the pollen cause hay fever. Native Americans harvested I. Xanthifolia due to its oil content.

Integrated Crop Management

Frequent soil cultivation suppresses this weed on arable fields. In rangeland it is necessary to maintain intact pastures. Overgrazing provides good conditions for I. Xanthifolia infestations.