Spotted knapweed flourishes in sandy soils. Figure 10 shows that the spotted knapweed known occurrences are in the north central portion of the West Creek watershed. Hoary cress is a creeping perennial, which reproduces by seed and creeping roots. The extensive root system spreads horizontally and vertically with frequent shoots arising from the rootstock. It grows erect from 10 to 18 inches high and has a white color.
Hoary cress is one of the earliest perennial weeds to emerge in the spring.
May. It grows in waste places, cultivated fields, and pastures, and is capable of vigorous grow on the irrigated, alkaline soils of the West. Yellow toadflax is found throughout most of temperate North America and is found in Colorado from 6,000 to 8,500 feet in elevation, mostly on western slope but also found on eastern slope. It prefers waste places, pastures, roadsides, cultivated fields, meadows, and gardens. It is found locally abundant and often around sites of former homesteads. Occurs in a wide variety of habitats, but is generally limited in wet or dark conditions.