Physocarpus capitatus Tilden Park

Physocarpus capitatus 'Tilden Park®' is a prostrate form of a robust but little-known Physocarpus, native to the western United States. Still not widely available, this unusual bush has a prostrate habit and forms a wide ground cover adorned with lobed and dentate leaves similar to those of maples, silky and purplish at budbreak, turning green at maturity. Its spring flowering, white and in large flat corymbs, is highly attractive to bees and butterflies, giving way to small red fruits that remain decorative on the branches until late in the season. Other advantages of this sturdy ground cover are its ease of cultivation in any slightly acidic to non-calcareous soil, and its good resistance to summer drought once established.

Physocarpus capitatus (synonymous with Opulaster capitatus or Spiraea capitata) belongs to the Rosaceae family, and is native to the western United States, from southern Alaska to eastern Montana and Utah, and south to California. It is mainly found in wet places, forming thickets along rivers and in forests. This very hardy bush shows a good tolerance to summer drought, to the point that it is commonly planted in Californian gardens. This Physocarpus gets its English name of "newbark" from the appearance of its scaly white bark, which peels off in ribbons as it ages, forming flakes. The name Physocarpus comes from the Greek 'phusa' which means air bubble or vesicle, and 'karpos' which refers to the fruit, in reference to the shape of the fruit.

The cultivar 'Tilden Park', discovered in 1963 in California, stands out with its prostrate, ramified and compact habit, supported by several "trunks" and branches that arch gracefully towards the ground. This bush has a medium to slow growth rate and will not exceed 1m (3ft) in height and 2.50m (8ft) in width when fully grown. In our gardens, it will reach a height of about 50cm (20in) and a spread of 1m (3ft) at the age of 10 years.

Its deciduous foliage may partially persist depending on the severity of the winter. It consists of large leaves, 8cm (3in) wide, slightly sticky and coloured purple at budbreak. The mature leaves are dark green, covered in fine hairs, deeply lobed, with serrated edges. Before falling, they turn yellow. The flowering takes place in May-June. The bush is adorned with a beautiful white flowering, in the form of tiny flowers gathered in dense, fluffy and flat corymbs, 8cm (3in) wide. This flowering is followed by curious red and swollen fruits that are appreciated by birds in autumn.

Physocarpus 'Tilden Park' is one of those shrubs that can thrive on their own once well established and can tolerate the root competition of large trees on the edge of a grove. Unknown to many gardeners, it is more often offered to professionals for urban landscaping, proof of its robustness and tolerance to pollution, summer drought and even sea spray. It will find its place along the edge of flowerbeds or groves, in sunny, semi-shady or even shady areas where it will keep weeds in check. For example, it can be combined with sturdy shrubs such as the hedge honeysuckle (Lonicera xylosteum), with light, golden foliage (Euonymus japonicus 'Aureovariegata', Leycesteria formosa 'Golden Lanterns'), or with silver foliage (shrubby wormwoods). It also pairs well with Japanese spireas, small viburnums (Viburnum trilobum 'Bailey Compact'), dwarf winged euonymus (Euonymus alatus 'Compactus') or Neillia (Neillia affinis). To accompany it, you can plant Heucheras or Heucherellas at its base. It also looks great planted in a container on a terrace or balcony.