Flowers and Plants for Northern Gardens

“Leonard Messel” hardy magnolia in bloom.

Magnolia trees conjure up images of genteel southern plantations and live oak draped with Spanish moss. Many northern gardeners aren’t aware of the several hardy varieties of magnolia that will grow and thrive as far north as USDA Zone 4.

Magnolias
Magnolias

I wasn’t aware of this until I saw a potted magnolia seedling (pictured at right) in bloom and for sale at the Farmer’s Market. You can be assured it is hardy in Minnesota and other Zone 4 areas.

The Star Magnolia, Magnolia Kobus var stellata, is one of the most common hardy magnolias grown. It is actually a large bush, growing about ten feet tall, with an upright, uniform appearance. Its branches spread out nearly as wide as it is tall and are somewhat tiered. Star Magnolia produces white blooms in late April or early May.

“Leonard Messel” and “Merrill” magnolias are the result of a cross between the tree-like Magnolia Kobus and its shrubby variety stellata. They both grow somewhat larger than the Star Magnolia. “Leonard Messel” has delicate, lovely pink blossoms with white inner petals and “Merrill” offers white flowers on an extremely vigorous and large growing tree.

The Cucumber Tree Magnolia, Magnolia acuminata, is so-named in reference to its fruit aggregates, which somewhat resemble cucumbers. This magnolia is grown primarily as a large and beautiful shade tree rather than for its flowers. These trees can grow to eighty feet tall and forty feet wide.

You’ll find potted magnolia trees at the garden center. Magnolias don’t like their roots disturbed so you’ll rarely if ever, find them for sale as bare root or balled and burlapped plants. When you get it home, plant it into its final growing place and leave it there.

Plant magnolias in full sun; they’ll grow in light shade, but will produce fewer flowers and exhibit less vigorous growth.

Make sure that the tree gets adequate water the first year after you plant it. Thereafter, it should do nicely fending for itself, although all trees benefit from artificial watering during times of drought.

Magnolia trees often live eighty years or more. What a legacy to leave to your grandchildren and their grandchildren.

Lilac Bushes Perfume the Air in Northern Cities

The lilacs are blooming. All over the city, their sweet fragrance permeates the air. Everywhere you look their delicate lilac-colored flowers light up individual lawn specimens or hedgerows of this hardy bush. The brief, two-week period that lilacs bloom every spring almost makes up for freezing winter weather.

Almost.

Lilacs are classified as Syringa vulgaris and are reliably hardy in USDA Zones 3 to 7.

Lilac Bushes
Lilac Bushes

Native to both Europe and Asia, lilacs are now grown around the globe. They have adapted well to urban environments. You’ll find stands of lilacs growing alongside highways and freeways, as well as the property lines of city and suburban lots.

Lilacs grow best in full sun, although they’ll do fine with as little as four hours of direct sun a day.

Plant lilacs in well-drained, slightly alkaline soil (add pulverized lime to sweeten). They don’t like their feet wet, so don’t plant them in low lying areas where the water stands after it rains.

Lilacs live for 100 years or more. If you live in the city, chances are the lilac bush in your yard has been growing there since the automobile was a “curiosity” and travel by horse and buggy was the norm.

If you’re lucky enough to have well-established lilacs growing on your property, you probably already know that they’ll continue to grow and bloom every spring with very little help from you.

Provide them with water in times of extreme drought and feed them with an all-purpose fertilizer in late spring after they finish flowering, although they’ll most likely thrive without your intervention.

Prune for size and shape at the same time you cut off the spent flower heads, right after they finish blooming. They’re very forgiving. I once watched a well-meaning neighbor “prune” his lilac bush by ripping off several of the large branches. I was convinced that the bush was history, but it bounced back and bloomed again in a couple of years. Go figure.

Just to be on the safe side, prune out no more than 1/3 of a lilac’s branches at a time. If the bush requires more pruning than that, wait until the following year and again, prune out no more than 1/3 of its branches.

Lilacs seem to last only a few hours as a cut flower before wilting. Here’s what to do to keep a bouquet of lilacs that will last longer: cut short branches, not individual flowers, making sure to cut them at the woody part of the stem. Lay the stems on a cutting board and smash the woody ends with a hammer. This will enable them to more easily draw up water and they will last indoors for several days in a vase. Change the water daily.

Add a few tulips and/or peonies for a spectacular looking spring bouquet.

No flowers smell as sweet as spring-blooming flowers.

Grow Rhododendron and Azalea in Cold Northern Climates

Hardy varieties of spring-blooming rhododendron and azalea grow in cold northern climates.

Most varieties of rhododendron are not wintered hardy in northern climates, but several varieties being tested at the Landscape Arboretum of the University of Minnesota are showing promise for successful growing in higher latitudes.

Azaleas, a deciduous variety of rhododendron, are somewhat harder and are the variety of choice for northern growers. Rhododendrons and azaleas are both considered subsets of the rhododendron genus.

Grooming Rhododendrons
Grooming Rhododendrons

Despite cold winter temperatures, rhododendrons thrive planted on the east side of buildings. This protects them from hot summer temperatures or winters sunscald, which occurs when the bark of trees or shrubs is suddenly cast into a shadow when air temperatures are below freezing. The sudden cold after the warmth of the bright winter sun heating up the bark on the tree is what causes the damage.

Plant rhododendrons in soil that is very well-drained and slightly acidic, the same type of soil in which evergreens grow well. Rhododendrons make good companion plants for evergreen shrubs and ground covers.

Amend the soil by adding peat moss, compost, and well-rotted manure. This will improve the soil’s fertility and moisture holding abilities. The acidic peat moss will also help lower the pH of the garden bed. You can also add sulfur or ferrous sulfate to lower the pH to an optimum level of 4.0 to 5.5 on the pH scale.

Apply a thick mulch to hold in moisture and prevent the growth of weeds. Rhododendrons are shallow-rooted, and their roots can be harmed by cultivation. They are also thirsty and will benefit from a water-retaining mulch. Water them well during dry summer weather.

Korean Rhododendron (Rhododendron mucronulatum)
Native to Korea, China, and Japan, this hardy, deciduous variety blooms in early May with magenta colored flowers. The flowers appear before the leaves. A pink cultivar, called “Cornell Pink” is as hardy as the magenta-flowered variety.

Rhododendron

Rhododendron P.J.M.
A cross between Rhododendron carolinianum and Rhododendron dauricum, P.J.M. is an evergreen rhododendron with small leaves and lavender-pink flowers. Hardy to -35 degrees Fahrenheit, it prefers sandy soil. This is a promising group of hardy hybrid rhododendrons and is currently being tested at the University of Minnesota Landscape Arboretum.

Mollis Azaleas Series
With flower buds hardy to -25 degrees Fahrenheit, the mollis series of hybrid rhododendrons (Rhododendron X kosteranum) bloom in late May in shades of red, orange and yellow. They grow about 6 to 8 feet high and wide at maturity.

Rododendron Pinkshell Azalea
Extremely hardy, Pinkshell azalea (Rhododendron vaseyi) has flower buds hardy to -35 to -40 degrees. Its delicate, pale pink flowers bloom before the leaves unfurl. It grows into a shrub with an open form, fitting well into natural gardens.

Northern Lights Azalea Series
A series of F1 hybrids, Northern Lights azaleas are a cross between Rhododendron X kosteranum and Rhododendron prinophyllum. Released commercially in 1978, the flowers are both prolific bloomers and extremely fragrant. Named cultivars–all featuring “Lights” as part of their name–are available with flowers in rose, pink, white, salmon, orchid, golden yellow and white with a golden upper petal. Developed and released by the University of Minnesota Landscape Arboretum, the flower buds of Northern Lights azaleas are hardy to -30 to -45 degrees.

Don’t forgo planting these spring-blooming beauties if you live in the far north. There are plenty of varieties of hardy rhododendrons to choose from. And don’t forget about azaleas, their deciduous cousins.

Leave a Reply

Your email address will not be published. Required fields are marked *