by snow cover, and make use of warm periods in winter for growth when the snow melts. Some common winter annuals include henbit, deadnettle, chickweed, and winter cress. Winter annuals are important ecologically, as they provide vegetative cover that prevents soil erosion during winter and early spring when no other cover exists and they provide fresh vegetation for animals and birds that feed on them. Although they are often considered to be weeds in gardens, this viewpoint is not always necessary, as most of them die when the soil temperature warms up again in early to late spring when other plants are still dormant and have not yet leafed out. Even though they do not compete directly with cultivated plants, sometimes winter annuals are considered a pest in commercial agriculture, because they can be hosts for insect pests or fungal diseases (such as ovary smut, Microbotryum sp.) which attack crops being cultivated. The property that they prevent the soil from drying out can also be problematic for commercial agriculture. Molecular genetics In 2008, it was discovered that the inactivation of only two genes in one species of annual plant leads to its conversion into a perennial plant. Researchers deactivated the SOC1 and FUL genes (which control flowering time) of Arabidopsis thaliana. This switch established phenotypes common in perennial plants, such as wood formation. See also - Plant that flowers & sets seeds once, then dies. References External links Garden plants