Does your garden lack the anticipation and excitement that it had this spring when shrubs like forsythia, spirea and lilac burst into glorious bloom? Shrubs and small trees are important in forming the backbone of the summer garden, serving as a green backdrop for colorful annuals and perennials. However, a number of these woodies can serve double duty by adding vibrantly colored flowers as well as rich green foliage.
A couple of commonly available and therefore, often over-looked summer bloomers are smooth hydrangea (Hydrangea arborescens) and panicle hydrangea (Hydrangea paniculata). ‘Annabelle’ is the most popular cultivar of smooth hydrangea -- a shade-tolerant, 3-4’ shrub which produces strong-stemmed, white flower heads measuring 1 foot across! Annabelle hydrangea blooms in late June or early July and is excellent for brightening up a moist, shady spot in the garden. Panicle hydrangea is a taller species reaching 8-10’ in height and performs best in full sun. A fine late-blooming form of panicle hydrangea is ‘Tardiva’. This cultivar produces white to pink, 8-10” long, cone-shaped flowers in late August or early September -- quite a late bloomer! It is often trained into an attractive single or multi-stemmed small tree. Both of these summer bloomers can be seen in the shrub borders surrounding Olbrich’s Herb Garden.
If fragrance is what you’re looking for in a summer blooming shrub, then take a look at summersweet clethra (Clethra alnifolia) and sweet mockorange (Philadelphus coronarius). Summersweet clethra is a small suckering shrub that reaches 3-5’ tall, grows well in sun or shade, and performs best in moist organic soils. The white-flowered cultivars ‘Hummingbird’ and ‘Paniculata’, and the pink-flowered cultivars, ‘Pink Spires’ and ‘Rosea’ are all deliciously fragrant garden-worthy selections blooming in early to mid-August.
The mockoranges, as their name suggests, fill the air with the sweet scent of orange blossoms in mid-June. They are all sun-loving, tough growers that are tolerant of heat and poor infertile soils. Bouquet blanc virginal mockorange (Philadelphus x virginalis ‘Bouquet Blanc’) is an excellent hardy, dense grower. It reaches 6’ in height and produces single or semi-double white flowers. The golden mockorange (Philadelphus coronarius ‘Aureus’) is clothed in lemon yellow foliage and is a knock-out planted next to other contrasting green-foliaged plants. The single white flowers tend to blend in with the leaves but the fragrance is sure to remind you that they are there!
If I had to pick but one summer blooming shrub it would have to be bottle-brush buckeye (Aesculus parviflora). This stately shrub produces spectacular white 8-12” long bottle-brush shaped flowers in early July. It grows equally well in shade or sun and prefers a somewhat organic soil that retains moisture, especially during long summer dry spells. Bottlebrush buckeye is a suckering shrub reaching 8-12’ when mature and is a somewhat slow grower, but is definitely worth waiting for!