It’s the season for the bright yellow branches of the forsythia, a clarion call to another growing season and a bright relief to a drab winter.
Alas, the flowering season is short for these often ragtail-looking shrubs and if the forsythia is the only flowering shrub in your world, you might think there’s no reason to investigate the genre further.
But there’s good reason. The landscape value of flowering shrubs is often overlooked as we search out the best trees or the newest perennials. And with prime planting season virtually upon us, there isn’t a better time in the year to earmark some pockets of the home landscape that could be brightened by such plants.
“Perennials are the big rage now and flowering shrubs are in scale with them,” says Kris Bachtell, horticulturist and collections manager at the Morton Arboretum. “We like that because it gets people away from the yew meatballs in front of their house. You don’t have to be manhandling flowering shrubs with pruning shears. That’s why flowering shrubs with ornamental grasses and perennials has caught on.”
The problem is to find a shrub that fits into your yard, and that will survive our harsh winters and thrive. What kinds should you choose and how should they fit into your landscape?
Forsythias are not Bachtell’s favorite plant because of their ungainly form and flowers that appear only if winter hasn’t been overly harsh. What he looks for is a shrub with multiseason appeal, one that flowers, looks good in summer, has colorfulfall foliage and hopefully adds winter interest in the form of its fruits or bark. Bloom times range from late winter to early fall and plant types range from those that die back to the ground every winter to those that hold their foliage year-round.
“Viburnums are some of my favorites; many can be grown in sunny or shady locations,” says Karen Heier, garden center manager of Schwarz Nursery in Addison. “Many of the viburnums such as Chicago Lustre do get quite large, but they get good fall color and good berries.”
Chicago Lustre is one of three cultivars of Viburnum dentatum that have been certified for the Chicagoland Grows program. The partnership between the nursery growers, the Morton Arboretum and the Chicago Botanic Garden introduces new or underused shrubs and trees that are especially suited to our winters and soil types.
The Chicagoland Grows viburnums are named Autumn Jazz for its multihued fall color; Northern Burgundy for its purplish fall uniform; and Chicago Lustre for its shiny green foliage. All three have white flowers in late spring and blue-black berries that are attractive to birds in late summer into fall. They will range from 10 to 15 feet tall and nearly as wide at maturity, which makes them a challenge to place in a small yard.
How to use them
How to use flowering shrubs is perhaps the largest challenge facing the average homeowner, Bachtell says. Just because the plant looks rather unimposing in a nursery container doesn’t mean it won’t attain height and heft over the next several years.
“You should pick a plant that will appear in scale with the area where it will be planted,” Bachtell said. “Many have to be hacked back to keep them in bounds. You should consider the scale of the plant and the bed and move a three-foot bed out to a six-foot bed to accommodate a shrub in a design aspect.”
Bachtell said most shrubs should be planted in a bed situation, rather than plunking them down in the lawn where they would be considered specimens. Beds approximate the relationship to forest canopy where shrubs thrive in the wild. They often form backdrops for flowers or become visual and actual barriers to frame a yard.
Planting
Shrubs should be planted in a good soil environment. If they are going into a bed, that soil should have been improved by loosening and adding leaf mold, manure and peat moss, Bachtell says. He prefers organic mulches to rocks or weed barriers.
“You should plant shrubs at the same height they were growing in before or slightly higher,” he advises. “If you have poor drainage in the bed, you have to use a species appropriate to that condition or build a mini-berm to get them above the soil. Drainage is very important for plants like rhododendrons.”
If you buy a container-grown shrub, check the root system carefully. If it is highly potbound to the point where it won’t come out of the container, “then the roots need to be loosened for it to have a good chance at survival,” Bachtell said. “For most plants, cut off the bottom roots if they are circling and manage the root ball carefully because it is planted in a highly organic mixture that dries out quickly.”
The other predominant way to buy woody plants is called “balled and burlapped,” where the roots are wrapped up in a cloth substance. It’s best to take off the burlap when planting, Bachtell says, but if you put the rootball in the hole and fold back the cloth, that should work as well. The key is to open the “ball” so the cloth is not above ground where it will act as a wick to let moisture evaporate from the planting hole.
“You then backfill the hole that is twice the size of the ball with good amended soil,” Bachtell says. “Poor drainage is one of the biggest factors of failure with shrubs. If it is near a foundation, make sure the soil is sloped away from the house. And make sure the back line of planting is out from under the eaves of the house so they can get rainfall.”
What likes Chicago
Because of our specialized conditions, many shrubs are not suited to the Chicago area. If you go to the library and check out books on the subject, the lush photographs more often than not contain wide vistas of rhododendrons and azaleas, shrubs that prefer far more acidic soil than our alkaline clay. One book I found fairly gushed over winterberry, a deciduous holly with red fruits. Although hardy in our winters, the recommended soil pH is 4.5 to 5.5. In most areas of Chicago, the soil pH is 7.5 and higher. In order to grow that shrub, you would have to virtually remove the native soil and create a bed using lots of acid-based peat moss.
Both the Arboretum and the Botanic Garden sell publications that outline the best shrubs and trees for the area, lists that are too long for inclusion here. However, several shrubs made the list of favorites of both Bachtell and Heier:
Small shrubs (under 5 feet):
– Black chokeberry (Aronia melanocarpa): Widely adaptable, white flowers, glossy foliage, excellent red fall color, shade tolerant.
– Fothergilla (Fothergilla gardenii), commonly called bottle brush: Smells like honey in spring, excellent fall color; needs good, organic well-drained acidic soil.
– Hydrangea aborescens Hills-of-Snow: Huge white flowers in summer; very shade tolerant; good with perennials like hosta to lighten up shady areas.
– Spirea x bumalda-“Anthony Waterer,” “Froebelii” and “Goldflame”: Dwarf versions of the bridalwreath spireas; multiseasonal; long flowering season; pink to lavender flowers.
– Potentilla: Small yellow flowers last all summer; if pruned properly, will look good from year to year.
– P.J.M. rhododendrons: Little-leaf types of the species do better in our winters and on our soils; pink-to-purple flowers in spring; need good drainage.
Medium shrubs (to 8 feet):
– Red chokeberry (Aronia arbutifolia): Very showy, attractive fruit display; tolerant of shade, wet soils and poor drainage.
– Palibin Meyer’s lilac: Small clusters of typical lilac flowers, formal globe shape. Miss Kim has more upright and larger clusters, although not as many. Both are predictable growers and stay in scale with the yard.
– Judd viburnum: Pink buds turning to white fragrant flowers.
Large shrubs (over 8 feet):
– Bottlebrush buckeye (Aesculus parviflora): Large brush-like white flowers around July 4; yellow fall color; shade tolerant, drought intolerant; may be hard to find because they’re difficult to establish in nurseries.
– American fringetree (Chionanthus virginicus): Long, olive-like leaves, long lacy fragrant flowers; olive-blue-purple fruits on female plants; likes moist conditions.
– European smokebush (Cotinus coggygria): Needs good drainage; looks like it’s covered by smoke in summer; good fall color.
– Witchhazels (Hamamelis virginiana and vernalis): Flower at odd times, virginiana in October to November, vernalis in February or March; best treated as shrubs instead of small trees; best grown when biggest canes are pruned out.
