hemp, applied to other plants furnishing textile fibres
蔴 centers on hemp and, by extension, other plants that yield textile fibers. The character is essentially a variant of 麻 with an added plant radical, reinforcing its botanical source.
蔴 is a variant form of 麻, with the addition of the grass radical 艹 to emphasize its plant nature. 麻 itself is a pictograph of hemp plants drying under a shelter, and 蔴 reinforces that botanical origin.
The grass radical 艹 sits above 麻, which already means hemp. Picture a field of hemp plants growing under a shelter: the extra grass on top reminds you it's a plant used for fibers.
For マ, imagine a mother (ママ, mama) weaving hemp fibers into cloth: mama -> マ, and the hemp plant provides the material.