Potentilla, known botanically as Cinquefoil, is a perennial herbaceous genus, cultivated for summer flowers and bright green foliage. According to the USDA, there are more than 134 known species and cultivars of potentilla and they are all related to the Rose family of plants. Potentilla is technically classed as a sub-shrub and even the largest species rarely grow above 3 to 4 feet tall, hence the plants are also commonly considered to be ground covers and can be used in under-plantings.The genus is extremely forgiving of whatever trimming you deem necessary and can quickly spring back from even drastic pruning when other cultural conditions are being met.
Trim your potentilla plants in the spring after the last hard frost occurs but before new green shoots emerge.
Mow down large swathes of low growing Potentilla cultivars with your lawnmower deck set to the desired height. Smaller patches of low growing types can be trimmed by hand, using pruning shears held roughly parallel with the soil and plant surface. Cut away any dead or discoloured foliage and as much living plant bulk as you wish to remove.
Prune larger potentilla cultivars as deciduous shrubs. Trim out any dead, diseased, broken or ailing branches, severing them at the crown of the plant just above the soil line. Selectively remove roughly one third of the oldest living branches down to the crown of the plant. This will rejuvenate the plant slowly over a three year cycle.
Renew a badly overgrown, leggy or misshapen potentilla be shearing off all of the plant to just 1 inch above the soil line. This drastic pruning will force a rush of green growth that will be dense and in the natural intended form of the plant.
Potentilla will recover quickly from even harsh spring pruning, producing a flush of green foliage growth. Hard pruning may diminish or severely limit bloom in that first summer but the plants will be back to full bloom the second summer after a hard pruning.