Primroses (Primula vulgaris) grow in perennial clumps. The plants have fibrous roots that expand and grow outward as the plant spreads. Dividing primroses provides you with new plants and prevents the old ones from growing too large. Split the plants into two in the spring or fall when temperatures are cool but not freezing. Primroses don't tolerate frequent division, but occasional splitting gives you new plants and likely won't have a long-lasting effect on the primrose flower's health.
Loosen the soil around the base of the primrose with a garden fork, approximately 4 to 6 inches out from the stems. Slide a spade under the roots and lift the primrose plant from the soil.
Brush the excess soil from the roots. Use your fingers to tease out as much soil as possible so you can see the roots.
Work your fingers into the roots. Tease the roots apart gently, dividing the primrose plant into two equal-sized clumps. Minor root breakage may occur as you divide, but the plant recovers quickly after replanting.
Plant the two new primroses in the bed at the same depth the plant was growing at previously. Water the newly divided plants thoroughly, moistening the top 6 inches of soil.
Divide primroses every two to three years to ensure the least damage to the plants. Spring division occurs after the plants have finished flowering. Dividing before they flower may inhibit blooming for the year.