Volunteer sugar beet
Sugar beet is a biennal plant. The large, succulent roots of sugar beet used for food and feed production are harvested at the end of the first year of growth. If left to grow, sugar beets will flower and produce seeds during the second year. Sugar beets are only allowed to flower for seed production, which mainly takes place in France and northern Italy.
The sugar beet's wild relative, the sea beet, Beta vulgarisssp. maritima, is an annual in southern Europe and a biennal or perennial in northern latitudes (Scandinavia, Ireland etc).
Beets predominantly reproduce by seed, although plants can sometimes grow back from portions of roots left in the field after harvest. Volunteer sugar beets are rarely observed growing among other crops, in ditches, or on roadsides. If volunteer sugar beets were to occur in subsequent crops, they could be controlled by agricultural practices (herbicides, tillage during seed bed preparation). Most seeds left in the upper 5 centimetres of soil will germinate. Seeds that are ploughed deeper may remain dormant until conditions favour germination. Beet seeds can remain dormant for over 10 years.
Problems with volunteer beets sometimes occur when planted on the same field for several consecutive years. Emerging annual weed beet from the seed bank can only be controlled by mechanical means, and only to a certain degree. Remaining volunteers can reproduce and could potentially cross with bolting, transgenic sugar beets.