Culm, in botanical context, originally referred to a stem of any type of plant. It is derived from the Latin word for "stalk" (culmus) and now specifically refers to the above-ground or aerial stems of grasses and sedges.
Malting
In the production of malted grains the culms refer to the rootlets of the germinated grains. The culms are normally removed in a process known as "deculming" after kilning when producing barley malt, but form an important part of the product when making sorghum or millet malt. These culms are very nutritious and are sold off as animal feed.
References
Culm (botany) Wikipedia(Text) CC BY-SA