A cold-hardy deciduous shrub that evokes memories of grandmother when its arching branches are laden with clustered white flowers in late spring and early summer, Spiraea x vanhouttei is a hybrid of Spiraea cantonensis and S. trilobata. The cultivar ‘Renaissance’ has all the ornamental charms of this old-fashioned shrub but virtually none of its usual leaf diseases. The dense domed flowerheads attract bees, butterflies, and ants in search of pollen and nectar. A twiggy plant that spreads by root suckers, this medium-sized shrub has small, blue-green, somewhat diamond-shaped leaves with lobed tips. They sometimes provide a second season of interest by turning rusty-red in fall.
Vanhoutte spirea grows and flowers best in full sun, but also produces a good display in partial shade. It tolerates many soil types, doing best in fertile, moist ground. It tends to spread via roots and seeds to form an unruly mass of stems. Remove unwanted stems in early spring and prune back remaining stems to strong new side shoots immediately after bloom. Use it massed in screens and informal hedges or individually as a specimen or shrub border plant.
Plant in spring or fall. Space plants 2 to 15 feet apart, depending on the expected mature size of the plant. Dig a hole only as deep as the root ball and 2 to 3 times as wide. If your soil is in very poor condition, amend the soil you’ve removed from the hole with a small amount of compost. Otherwise don’t amend it at all. Carefully remove the plant from the container and set it in the hole. Fill in around the root ball with soil until the hole is about half filled. Then firm the soil and water thoroughly. Fill the hole with the remaining soil and water again. Form a raised ridge of soil around the perimeter of the hole so it acts like a berm to help hold in water.
Apply a layer of compost under the tree each spring, spreading it out to the dripline (the area under the outermost branches). Add a 2-inch layer of mulch to retain moisture and control weeds. Water plants during the summer if rainfall is less than 1 inch per week. Deadheading spent flowers will sometimes induce a second flowering. Most spireas can be pruned after flowering to reduce height and maintain the desired shape. However, Japanese and bumald spireas should be pruned in early spring to promote the best flowering. Remove dead, diseased, and broken branches anytime. Spireas can be severely pruned and will grow and flower again.
Winchester Gardens generally stocks this item.
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