Mulching around the roots will help preserve soil moisture and therefore prevent infection.
The best way to prevent powdery mildew forming is to grow your spiraea in full sun and to water regularly in dry weather. It is easy to grow, low maintenance and ideal for mass. Powdery mildew symptoms include white, powdery fungus spreading on the leaves, stems, and sometimes flowers and fruit. Magic Carpet Spirea is deer resistant and thrives in full sun in rich, evenly moist, well-drained soils. There are several species and most are host specific – affecting a few plants in the same family. Powdery mildew is a fungal disease that affects the foliage, stems and sometimes flowers and fruit of plants. In poor soil that's liable to dry out, powdery mildew may appear on the leaves. Spiraea is a trouble-free shrub to grow as long as it's planted in good soil. Some spiraeas form spreading clumps and produce shoots on the outer part of the clump (called suckers) which form roots at the base: these can be detached and planted separately. Take semi-ripe cuttings of non-flowering shoots in mid to late summer. After several years, take out about a quarter of the oldest stems near to the ground, which lets light and air through the centre and encourages fresh new growth to develop. Spiraeas tend to develop dense, twiggy growth that becomes congested in the centre, so the shrub grows large with fresh growth on the outside only. Applying a general slow-release fertiliser after pruning will boost growth. As with all border shrubs, a spring mulch of well-rotted organic matter will keep the soil – and therefore the plant – in good condition.
Spiraea is hardy and doesn’t require any special winter care. Once established, spiraea needs little attention apart from pruning. Spiraea japonica Magic Carpet Plant Size Height Up to 60cm (23.6in) Spread Up to 60cm (23.6in) Hardiness & Longevity Hardy Shrub Position In Full sun. Plant with the top of the rootball at the same depth as the soil level, firm in, and water well to settle the soil around the roots. Clusters of deep pink flowers cover the plant in early summer and. Planting can be done while in full growth in spring or summer, as long as plants are watered regularly. Vibrant red shoots emerge in spring and mature into rich bronze, red-tipped foliage. Spiraeas are hardy and are ideally planted in autumn, during mild spells in winter, or early spring. A fairly low growing spirea cultivar that is somewhat similar in coloration to Goldmound Spirea, but not quite as intense of a lime green color to the foliage. Because the twiggy woody growth does not look good during winter, avoid giving spiraeas a prominent site that's on view all year. The smallest spiraeas give the best effect if planted in a group of three. Depending on plant size, site your spiraea towards the back, middle or front of the border. Improve poor soils by adding well-rotted organic matter before planting. Grow spiraea in garden borders in fertile, well-drained soil.