Plant Guide - Weed Identification

Leafy spurge is a long living perennial with an incredibly vigorous root system. The extensive roots of the spurge plant can reach depths of 30 feet and contain nutrients that will sustain the plant for long periods of time. The brownish roots have pink buds on them, each of which develops into new shoots. This allows the plant to reproduce by seed and by root. Seedlings resemble small pine trees and closely resemble yellow toadflax seedlings as well. All parts of the plant, when broken off, will produce a milky sap. Stems of the plant can grow up to three feet in height and have alternate, narrow, smooth margined leaves. Leaves and stems are a bluish-green in color. Depending on climate, flowers will start blooming in early June. Flowers are a yellow-green color and arranged in clusters containing seven to ten flowers. The showy, heart shaped yellow bracts surround the flower. When this plant goes to seed, it produces grayish-brown oblong seeds in a three-celled capsule. At maturity, these capsules explode launching seeds up to fifteen feet from the parent plant.

Look for dark roots with pink buds on them, and break apart any part of this plant and you’ll find a milky white latex. Once recognized, leafy spurge is easily identified by its distinctive yellow-green flowers.

Leafy spurge is a flexible plant that tolerates extremely dry to extremely wet soil conditions. It can often be found along waterways and irrigation ditches, but also found in draws and sagebrush. It grows in a wide variety of soil types but is most abundant in sandy or gravelly soils and in arid conditions.

Purple loosestrife is a perennial that can grow up to ten feet in height and typically prefers moist or riparian habitat. Due to the numerous four-sided stems that are green to purple in appearance, this plant appears woody and bush-like in appearance. Clasping leaves have smooth margins, are lance shaped,  and are heart-shaped or rounded at the base. Purple loosestrife leaves and stems are covered by downy fine hairs, and leaves are whorled or alternate on the stem. In autumn with dehydration, the leaves of purple loosestrife turn red in color. The showy purple to magenta colored flowers are clustered on a long spike that can extend two inches to three feet down the stem called a raceme. Each flower has five to seven petals and blooms from June to September. Seeds burst at maturity around late July or early August, with each stem producing up to three million tiny seeds per year. Purple loosestrife has a dense, woody, and extensive root system. This root system and the prolific seed production results in rapid spread of loosestrife. In addition, stems of the plant that are broken off or disturbed often grow shoots.

The square or octagonal stems, the red leaves if the plant gets dried out in the fall, and the long clusters of showy purple to rose colored flowers.

As a general rule, moisture is required for growth and reproduction, however, well-established plants can persist on dry sites.  It is well suited to seasonal wetlands, and is capable of invading wet meadows, river and stream banks, pond edges, reservoirs, and ditches, irrigation canals, and marshes.

Saltcedar is a pretty evergreen shrub that can grow up to fifty feet in height. As an invasive shrub, saltcedar can form dense thickets of vegetation, especially along waterways. Leaves resemble juniper leaves; they are scale-like, overlap each other along the stem and are gray-green in color. Stems of saltcedar are slender, light red or orange-colored and flowers are pale pink to white and form dense masses of 2 inch long spikes at the branch tip. Dense plumes of flowers bloom from early spring to late fall, and each plant can produce 600,000 seeds annually. Saltcedar reproduces by root and seeds which are dispersed through water and air. This plant prefers riparian areas, but can be found in drier soils as well.

The evergreen shrub appearance and the showy pink flowers that bloom in clusters along tips of stems.

Saltcedar is located along streams, waterways, bottom lands, banks and drainage washes of natural or artificial water bodies, moist rangelands and pastures, and other areas where seedlings can be exposed to extend periods of saturated soil for establishment. It has also been found in numerous ornamental locations in urban areas in western Montana. These areas are not typically riparian in nature.

Canada thistle is a familiar perennial in Montana as it is found in every county in the state. It can reach heights of four feet and forms deep and extensive root systems, making it difficult to control. Creeping horizontal roots sprout new plants and can reach more than nineteen feet in one season. These roots can also go as deep as twenty two feet. Rosettes are smooth, have irregular lobes and have spine tipped edges. Thistle leaves are distinctive as they are thorny, alternate and deeply lobed. Leaves are lance-shaped and  the edges have yellowish spines, making hand pulling a thorny proposition. Stems can grow tall, are often branched, slightly hairy, and lack spines. Flowers resemble spotted knapweed in that they are pink to purple and ray-like. Canada thistle produces both female and male flowers and both genders must be present for the plant to go to seed. Male flower heads are globe - shaped while female flower heads are flask-shaped. Canada thistle flowers tend to be smaller than other thistle species. Each female flower prodces a single, tan curved seed which has a papery covering and is easily tossed about by the wind. One plant is capable of producing over 3,000 seeds annually. This plant reproduces by both seed and root, but primarily from the roots.

Roots that are creeping, extensive and deep, spines on the tips of the leaves, and pink flowers that resemble spotted knapweed.

Canada thistle is found in open areas with a moderate amount of moisture but does poorly on wet soils lacking sufficient oxygen.  It can grow on many different soil types but it does not grow well in shade and is rarely found within wooded sites, except in clearings. It is commonly found in abandoned fields or lots, abandoned gravel pits, pastures, right-of-ways , roadsides, railway embankments, lawns, gardens, and agricultural fields. It also invades wet areas with fluctuating water levels such as stream banks or irrigation ditches and sloughs.

Like its close cousin yellow toadflax, Dalmatian toadflax produces showy snapdragon-type yellow flowers, however, it is easier to identify due to its long, erect appearance and waxy coating. Dalmatian toadflax has a tap root that can go as deep as ten feet, but will also produce lateral roots that can extend out from the parent plant for ten to twelve feet. This plant can produce woody stems that are capable of reaching hieghts of four feet. They can be branched in the upper portions and are often a blue-green in color. Both stems and leaves have a waxy coating. Leaves are heart shaped and clasp the stem alternately. They have smooth margins. Blooms are nearly identical to yellow toadflax flowers: pale to bright yellow with orange throats and a spur extending from the bottom. Flowers are arranged in racemes on the stems and flowering occurs from mid summer to early fall. Seeds are ½ inch capsules that contain tiny dark seeds with papery wings. These seeds can remain viable for up to ten years and each plant can produce up to 500,000 seeds annually. Dalmatian toadflax reproduces by seed and by root.

Tall, stalky plant with waxy, rubber-like leaves and stem; stem and leaves are a bluish-green in color and flowers are bright, showy, yellow and resemble snap dragons.

Dalmatian toadflax grows best in full sun on dry sites with coarse textured, well-drained soils.  Dalmatian toadflax is typically found along disturbed sites, roadsides, clear cuts, transitional forest-grassland, right-of-ways, fences, cultivated fields, pastures, and rangelands.

Houndstongue is a biennial forb that forms a deep tap root and basal rosette the first year. It forms a flowering stem in its second year. The rosette leaves are broad, oblong, petioled and resemble a dogs tongue in shape. Leaves are alternate, up to one foot in length and up to three inches wide. They have smooth margins and are soft and velvety to touch. In the second year, stems form and often branch at the top of the plant. Plants can grow up to four feet in height. Flowers are five petaled, reddish-purple in color and produce four triangular, rounded seeds. They typically bloom in June and July. Seeds are small brown nutlets about 1/3 inch in length that easily attach to animals, vehicles, and humans. The entire plant has soft white hairs on it.  The single tap root of houndstongue is thick, black and woody. Houndstoungue reproduces from seed only and each plant can produce up to 2,000 seeds. The plant dies after its second year.

The soft white hairs covering the plant, the basal leaves that resemble a hounds tongue, and the little brown burrs that stick to everything.

Houndstongue prefers well drained, relatively sandy and gravelly soils. It can also be found in shady areas and especially under the canopy of forests and wetter grasslands. It can be found in pastures and meadows, along roadsides and in disturbed sites.

Spotted knapweed is a short-lived perennial or biennial plant that can grow up to four feet in height. This plant has a strong taproot as well as lateral roots. The rosettes of spotted knapweed are grayish-green in color with leaves that are up to six inches in length. Leaves are oblong and wider at the tip, deeply lobed and in early stages, covered with a layer of fine hairs. Stem leaves are alternate and may be slightly lobed or even unlobed. Each rosette may produce many stems. This plant will adapt to mowing and grow shorter and shorter to bloom at very low heights, which is why this plant can vary in height from two inches to four feet. Stems and leaves are a blue-green color but the short, thin hairs on the leaves can give the plant a silver-gray cast. One flower pink to pinkish-purple flower grows on each stem. Flowers are surrounded by oval bracts with black tips, thus the name spotted knapweed. One plant can produce up to 300 flower heads, thus producing up to 140,000 seeds. Flowers, which bloom from June to September, resemble both Canada thistle  and the popular bachelor button, a close relative. Seeds are oval, brown and up to 1/8 inches long with a short tuft near one end. Reproduction is primarily by seed, but can sometimes start shoots from a lateral root system. Dead plants that have gone to seed are readily identifiable by the tall cream colored to gray stalks and white to gray seed heads.

Pink to purple bachelor button - looking flowers, bracts with black tips directly under the flowerhead and deeply lobed lower leaves with fine, cobweb-type hairs.

Spotted knapweed is a highly adaptable plant. It can be found at various elevations, in moist or dry conditions, is shade tolerant but can be commonly found in sunny areas and prefers well drained or gravel/sandy soils. It can be found nearly everywhere in Montana. If it has a preference, it will thrive in sunny, arid conditions in course soil and especially in disturbed areas.