Ninebark, or Physocarpus opulifolius, is a large deciduous shrub that produces tiny white or pinkish flowers from May through June in cold climates, and from summer to summer in temperate regions. Red fruits ripen in the fall. Stems grow straight, then arch downward forming a fountain shape. They look best when allowed to grow as they please. Hardy in USDA Zones 2 to 10, these plants are the lazy gardener’s dream come true. They don’t care whether it is hot or if it’s brutally cold. Ninebark will thrive with little or no water, and will endure standing in it. It's not fussy about soil, either--a little sand to a little clay works fine. Add to this that the shrubs are deer, rabbit, and disease resistant, and drought, heat, and humidity tolerant, and you’ve got the perfect plant. Ninebark is a tough, trouble-free addition to just about any setting.
Water young ninebark only enough to moisten the soil evenly during its first year. Let it dry out a little before watering again. In subsequent years, these amazing shrubs will tolerate any moist to dry conditions occurring naturally. Ninebark is extremely drought tolerant once established.
Adjust pH only if it doesn’t fall into the 4.5 to 8.5 range. It’s highly probable that your soil’s current pH is perfectly suitable.
Provide your ninebark with adequate lighting. Part shade to full sun is fine.
Feed this shrub once each spring, whether it needs it or not. If it makes you feel better, it’s true that all plants can benefit from some fertilization. A single annual application of an all-purpose product is adequate.
Prune your ninebark during the winter, or in the spring right after it has bloomed. Just remove any dead wood, and thin out about a quarter of the stems down to the base. This will keep the plant from becoming leggy, and will enhance bloom production.
Cut this shrub back by half following flowering every several years. This will keep it shapely and under control.