Evergreens are a mainstay of the garden in winter and Kansas City’s manic-depressive climate can really create some wear on such plants. Evergreens can be divided into two categories: broadleaved like magnolia and holly and needle-leaf, which includes the conifers. The following is an overview how some of Powell Gardens’ evergreens have weathered the winter so far. It has been a wild ride with temperatures around zero but back into the 60s on a bi-weekly basis; and all this with little or no snow cover. (Snow is the best winter mulch against cold!). The coldest temperature has been -4F one morning.
Southern Magnolia (Magnolia grandiflora) grows at its northern limit in the Kansas City area and its leaves are often burned or even killed by hard winters. This is our small, but established ‘Kansas City’ Southern Magnolia, which is a rooted cutting off the champion Southern Magnolia tree in Kansas City. The parent tree has withstood the test of time and severe winters long into the past as it was brought here by an African American from Mississippi more than 80 years ago. The parent tree is over 40 feet tall and wide with a 18″ diameter trunk. Our young plant has held up well with just slight bronzing to the branch tip leaves. You can see we have allowed the plant to have foliage to the ground which helps protect the trunk in winter.
Here are winter damaged leaves of our ‘Twenty-four Below’ Southern Magnolia. This cultivar of Southern Magnolia is considered one of the hardiest, surviving -24F without injury. Ours has burned on the sunny side from much less cold because it is exposed on the south side of a warm wall. It gets too warm during the day then quickly drops when the sun goes down — this shocking change of temperature causes the damage, not the ultimate low temperature. By spring, you will be amazed how quickly this winter damage will recover. If this has happened to your own tree, not to worry.
Southern Magnolias sheltered against the north walls of the Visitor Center show much less winter burn because they do not warm up so much during the day. The left evergreen is actually an American Holly but the pyramidal central tree is our selected ‘Margarite‘ Southern Magnolia and the big magnolia on the right / background is the the hardy cultivar ‘Edith Bogue.’
This broadleaved evergreen is the poorly known and poorly named Devilwood (Osmanthus americana), which is native to the Southeastern United States. It can become a small tree with very glossy evergreen leaves. This plant is quite hardy once established and as you can see has no damage to its winter leaves.
Nandina or Heavenly Bamboo is a Japanese broadleaved evergreen that is marginally hardy in our area. As you can see this Compact cultivar’s foliage has been killed by the -4F cold. Again, we don’t let this bother us because it will quickly releaf in spring as the stem has not been injured — the winter killed leaves are the color of winter grasses. Our Nandinas have killed back to the ground in colder winters but have resprouted each spring.
Leatherleaf Grape-Holly (Mahonia japonica) has leaves that have withstood the cold but I can’t quite tell how the “spider” of flower buds atop the leaves have fared. This is one of the first shrubs to bloom, often in February. The flower buds start to emerge in fall and are hardy to around zero or only slightly below. They are very fragrant and yellow when in bloom; last year our shrubs did bloom in March and were awesome. This is a good indicator of moderating winter lows in our area as this shrub never was hardy here until recent years.
Some normally very hardy shrubs like this ‘Green Velvet’ Boxwood (Buxus hybrid) show some tip damage to leaves. This is because it was trimmed too late in the season and new twigs emerged and didn’t harden off well before winter’s cold. The burned leaves can easily be trimmed off and the shrub will quickly recover in spring.
Needle leaved evergreens like the Juniper (low and spreading) and the Oriental Arborvitae (Platycladus orientalis) are better adapted to the ups and downs of our winter climate. Oriental Arborvitae is a good choice for our climate, actually better than the American Arborvitae (native to the Great Lakes region) because it handles our hot and often dry summers much better. (There actually is a ‘DD Blanchard’ Southern Magnolia in the left background of this shot, too.)
This is the lush green foliage of the Hiba Arborvitae or Elkhorn Cedar (Thujopsis dolabrata var. hondai). This shrub is very marginal in our area because it is from Northern Japan in a cooler, more benevolent climate. It is sited off the northeast corner of the Visitor Center where it remains cooler in summer and is protected from winter winds by other evergreens. If you like a particular marginally hardy plant, be sure to know its needs and plant it in a microclimate that suits it.
Here are Golden Threadleaf Sawara False Cypress (Chamaecyparis pisifera ‘Filifera Aurea Nana’) — quite a mouthful but a very adaptable, diverse and beautiful evergreen from Japan. We have never had winter burn on any cultivar of this species.
This is a cultivar to the sister species to the above, the Hinoki False Cypress (Chamaecyparis obtusa ‘Nana Gracilis‘). Hinoki Falsecypress has some of the most beautiful and luxuriant sprays of evergreen foliage but is very marginal in our area. I am pleased most of ours are doing well sheltered on the east side of the Visitor Center.
Off the north end of the Visitor Center this ‘Glauca Nana Aurea’ cultivar of the Hinoki False Cypress has burned needles. It will recover in spring and probably survive the winter better as it becomes more established and as neighboring evergreens grow and help shelter it. Always try to give your plants an extra chance!
Here you can see the ‘Glauca Nana Aurea’ Hinoki Falsecypress in full (the golden muffin of a shrub lower left!). It has a ‘Blue Pagoda’ Blue Spruce (Picea pungens) and a groundcover of sedums dwarfing it. It still makes a nice golden contrast with the blue spruces. We bought these interesting blue spruces as ‘Blue Pagoda’ but that is not a cultivar name accepted by the American Conifer Society. We don’t actually know what they really are even though we are often asked by visitors where they can get one! A lovely dwarf blue spruce at any rate.
The beautiful bicolored needles of this Golden Korean Fir (Abies koreana ‘Aurea’) almost feel like AstroTurf. This is a much loved ornamental conifer but very touchy in our climate. I am so happy ours is doing great in a cool, raised bed with a Acrocona Spruce sheltering it from summer heat and winter wind.
Our Lacebark Pines (Pinus bungeana) are unfazed by the winter weather and are another choice evergreen for our climate as they come from Northern China with similar winter weather. They do not have the typical pyramidal form that most people demand from a pine but this plant will inspire many future generations on their visit to Powell Gardens as over time they will get the most beautiful bark of any pine. Bark of mature branches will flake off in a patchwork of silver, gray, olive and white — a reason this tree is often grown near Chinese Temples. Lacebark Pine is a much deserving Plant of Merit that everyone should consider planting for future generations to enjoy. It also has large edible pine nuts so is included our future Heartland Harvest Garden.
Come out and take a stroll around the grounds and enjoy the wide array of evergreens planted throughout Powell Gardens. You will have a great outdoor experience of exercise and fresh air to go along with ideas for your winter landscape.