Crabgrass is an annual weed. Living for one year, producing seed and then dying. Their offspring take over the following year and so on.. This weed grows during the warmer season but it can grow in any temperature region. Crabgrasses belong to the genus Digitaria, which is named from the Latin word for finger because of the finger-like appearance of the flowering part of the plant. There are smooth and large versions of Crabgrass. The smooth versions grow to a maximum of 6 inches and will not retreat even if mowed. The larger versions of crabgrass is very tall, reaching heights up to 24 inches. This type is less resilient and will be affected if cut short. Crabgrass can be killed off early in the year before it’s able to reproduce seeds giving it less of a chance to reappear the following year. However, crabgrass that has had a chance to lay seed can lay dormant for many seasons then make a sudden come back without warning.