Shrubs: The Backbone of a Beautiful‚ Functional Landscape
Shrubs do more work on the landscape than nearly any other plant in the garden․ They hold the soil on slopes‚ filter the air of pollutants‚ and provide food and shelter for wildlife year-round․ They also provide the backbone of the garden where perennials and annuals cannot fill in․ If you are in Tennessee or anywhere else in the Southeastern United States‚ the right shrub plants can grow well in our clay‚ hot and humid summer climate and USDA Zones 6-8․
We'll start by taking a look at these little beauties and then we'll explore very practical reasons that every yard should have a few shrubs around․
Blue Hydrangea: The Soil Chemist's Delight
One of the few flowers that easily changes color is Hydrangea macrophylla․ A high content of Aluminium in the soil plus a pH of less than 5․5 produces true-blue flowers; on the other end of the pH range‚ with no aluminium‚ or neutral to alkaline pH‚ the flowers are pink to red․ In the naturally acidic clay soils of Tennessee‚ blue flowers can easily be grown by most home gardeners with a sprinkle of aluminum sulfate in early spring․
Blue Hydrangea grows in partial sun (morning sun and afternoon shade are best․ By 1 p․ m․ full exposure to the high heat and humidity on summer afternoons in Tennessee will scorch the leaves․) with blooms from late May through August․ The plant grows best in a moist‚ well-drained soil‚ but once established can withstand periods of drought; newly transplanted specimens need to be watered regularly for the first season․
Snow Hill Hydrangea: Reliable Blooms in Tougher Light
The Snow Hill Hydrangea (Hydrangea arborescens 'Grandiflora') is the workhorse of sunnier locations; it produces a white flower ball in summer‚ 8 inches․ The acidity/alkalinity don't matter (although the Blue Hydrangea prefers acid soil); there is no need for science experiments․ Native to North America‚ it will grow in everything from shade to nearly full sun as long as it is watered․
It also flowers on new wood‚ so if the tops are killed by a late frost‚ as unfortunately happens in Middle and East Tennessee more than you may think‚ it is of no consequence‚ as the plant will be developing new stems in the spring anyway․
Maple Leaf Viburnum: The Understory Native
Maple Leaf Viburnum‚ Viburnum acerifolium‚ is a native shrub planted in many of Tennessee's wooded lots and is named for its three lobes that resemble a maple leaf․ In the fall‚ the leaves turn pink‚ burgundy and purple creating a fall show to rival any tree․ In the spring small clusters of white flowers are present․ The blue-black berries develop in late summer‚ and are quickly consumed by songbirds‚ most years within a few weeks․
Being a native plant of the shade‚ it can be planted underneath trees either in partial shade or in deep shade․ It is a suitable ground cover plant that can be used under large trees like oaks and hickories in the shady area of a house where grass does not grow․
Arrowwood Viburnum: The Wetland Workhorse․
Viburnum dentatum (Arrowwood Viburnum) tolerates wet feet more than most ornamental shrubs and is used for planting in drainage ditches‚ rain gardens and low spots which remain effectively boggy following the spring rains which are common in Tennessee․ Features of Viburnum dentatum include dark glossy green leaves and white flat-topped clusters of flowers in May․ Bluish-black berries can persist through winter and are used by birds and other wildlife when other food sources have been depleted․ Therefore the plant is considered to be one of the more important late-season wildlife shrubs․
Mature plants are 6 to 10 ft (1․8 to 3․0 m) tall and wide‚ and should not be planted among other plants too closely; in good environments‚ it reaches its full height and width within two to three years․
Beyond Beauty: The Role of Shrubs
Erosion Control That Actually Works
Fibrous rooting of a shrub collectively mat in the top 1․5 feet of soil‚ the layer of soil most likely to be removed by washout during heavy rain․ On slopes of 15% gradient or greater‚ fibrous rooting of a shrub would be more effective at preventing erosion than shallow rooting grass․ This is one reason we recommend shrub plantings along creek banks‚ property borders or along the grade‚ and in depressions where water stands and runs on properties in Tennessees rolling hills after a storm․
Cleaner Air‚ One Leaf at a Time
Additionally‚ the leaves of the shrub perform photosynthesis‚ absorbing the carbon dioxide and emitting oxygen into the air․ It's just like any other plant‚ really․ Especially with a shrub with large or fuzzy foliage (e․g․ viburnums)‚ the leaf material itself can also act as a filter and trap particulates‚ pollen‚ etc․ before they are blown further (which is why a shrub can have the greatest bulk of foliage on the street side‚ but can still be a good filter to catch the dust outside the space)․
Their Home‚ Not Just Decor․
For innermost nester birds such as sparrows‚ wrens and cardinals‚ the interlocking canopy of understory branches of a mature shrub border protects nests from hawks and other aerial predators‚ yet are high enough off the ground to avoid nest predation by ground-dwelling creatures․ Berries of viburnum and various other shrubs are used as an important food source by birds during autumn migration when berries are less abundant․ Hydrangeas and viburnums are important nectar sources for bees and butterflies․ Shrub-covered habitats such as many gardens have a great variety of these․ In contrast‚ single trees surrounded by lawns offer less variety and hence encounter fewer visitors․
Getting Started
Tennesseans should plant from late fall to early winter (October through early December)‚ when soil is still warm‚ roots will grow‚ and foliage demand less․ Spring is also acceptable; plants require more water for establishment during their first summer․
TN Nursery will ship all of these shrubs‚ including Blue Hydrangea‚ Snow Hill Hydrangea‚ and viburnums‚ at a size and root condition that will allow you to stick them in the ground in your yard and not in a small nursery pot to take years to fill in․ Erosion? More birds in the yard? Curb appeal in all four seasons? These four shrubs cover a lot of ground between them‚ sometimes quite literally․
