Structure in the Garden

Winter. The best time to see the structure in the landscape.  There are no flowers to cover, camouflage, or distract from form in the garden. 

What plants are creating that structure?  Trees and shrubs play a huge role in this picture.  Supporting roles are provided by the flower stems and seed heads of the perennials and grasses left after fall frost and freeze.

Our gardens, as they change through the seasons, can look just as wonderful through the winter as they do in the summer. Appreciating the browns, rusts and tans of the supporting plants and recognizing the stars of the show are our trees and shrubs can make our winter landscapes beautiful.

When we look in the forest, what do we see?  Trees and shrubs, mostly deciduous, form the structure. But, when finding an evergreen tree or shrub, the impact of that plant is great, and provides shelter and food for the critters that live there through the winter.

How can that be recreated in your landscape?  Choosing native shrubs and trees will help to provide the needed food and shelter for the insects, birds and mammals that live here. Also, look towards some evergreens to help create spaces in the yard. 

Although evergreens are not our main plant source in the forest, we do see some plants that hang on to their needles or leaves in the winter. Take, for example, the Eastern Red Cedar, Juniperus virginiana. This evergreen is native, grows to 30’ or so, and can be found in abandoned fields, along wood’s edges, and just about anywhere it can take root, if it has some sun.  In the landscape, it can be used as a screen, or even an evergreen specimen.  If you’re lucky enough, this tree will be a female plant and produce blueberries. Yes, there are male and female plants. The males will not produce the berries.

In the “wild” you may find an evergreen tree called Eastern White Pine, Pinus strobus. This tall evergreen can get as big as 100’ high!  Its needles are clustered in groups of 5, a true identification feature of this tree.  It may be grown as a Christmas tree, as it does well when pruned as a young plant. It has been used as a screen, provided there’s plenty of room for it to grow.  The needles are soft to the touch, and bluish in color.

An American holly is a lovely evergreen native to PA.  Its pointy leaves make it a prickly plant, but one of great texture. The female American holly produces berries, provided a male holly is close by. The red berries shine against the dull green leaves. Reaching 25’, it is a slow-growing plant.  It does not like the north winds, which tend to dry out the leaves, causing brown edges or dropping of the leaves.  It also prefers a more acidic soil, so planting in the right location will allow it to prosper.

Another holly that is native to PA is the inkberry holly, Ilex glabra. It can be found in coastal states from Maine to Florida, and across the southern states. It prefers sandy, moist, acidic soil but tolerates many soils. Full to part sun is best, but this plant can be in some shade as well and do just fine.

The inkberry holly maintains a height of 4’-5’, making it great in a foundation planting. There are many cultivars available, like ‘Shamrock’, Compacta’, and ‘Gem Box’, all selected for their size, tolerance of soil types, and color. This plant, like most hollies, is dioicous, meaning there are male and female plants.  The berries on this shrub are insignificant to our eyes, but to the birds, they are candy. A great plant to add to any landscape.

Other evergreens that we may see in our natural world include Rosebay rhododendron, rhododendron maximum, and mountain laurel, Kalmia latifolia. Both take shade, and like acid soils.  A pH of 4.5 – 6 will do best for these plants. Well-drained soils with rich organic matter will provide a nice home for the shallow roots. Both flower in late spring and are a joy to see in the hemlock forests.  At home, they must have organic soil, with a low pH, and semi-shade for their happiness. The mountain laurel has light pink to almost white clusters of flowers, while the rosebay rhododendron boasts a rose-to-pink flower color.  Rosebay rhododendron will get up to 25’ tall and the mountain laurel can reach 15’ when happy. Both are broadleaf evergreens, which means they keep their leathery-like leaves through the winter. 

Other, non-native evergreen plants that we may add to our landscapes include blue hollies, English hollies, and spruces.

White spruce, Picea glauca, although not found in PA, is native to New England.  They prefer higher elevations, but can be grown here in PA. We have them happily growing on our property as a screen planting from the road and backdrop for our meadow. Ours are almost 30 years old and have grown to 30+ feet. They need full sun and well-drained soil to persevere.  They have a faint bluish cast to the needles.  As with all spruce, the needles are held singly on the stem and prickly to the touch.

Blue hollies, Ilex x meservaea, do very well in our climate. In the 80s and 90s it seemed that every new planting had a few blue hollies along the foundation of the house, and for good reason. These plants have a dark green leaf color, and produce big, red berries.  They are a shrub, and probably will get to 6’ tall, but can be maintained a bit smaller. They are a cross between two species, hence the “x” in its scientific name. Here are some common cultivars of blue hollies:

• Ilex x meservaea ‘Blue Princess’ and Blue Prince’.  These have great leaf color – dark green leaves and dark stems.  The berries are bright red, a great contrast with the dark foliage.  Great for foundation plants and hedges. 
• Ilex x meservaea ‘China Girl’ and ‘China Boy’. These plants have lighter colored foliage, and in my experience, are a bit larger in size than the Blue Princess.
• Ilex x meservaea ‘Golden Girl’. This female holly has golden berries with dark green foliage, a nice change and contrast to the red berried plants.  As with most blue hollies, this one will get about 5’ tall and rounded in habit.  The male partner is ‘Blue Stallion’.  ‘Blue Stallion’ can be used to pollinate most of the female blue hollies.
• Ilex x meservaea ‘Dragon Lady’. This is one of my favorites of the blue hollies.  Unlike the cultivars mentioned so far, this one is pyramidal, not rounded.  It reaches easily 20’ and is relatively slender for the height of the plant.  Like all blue hollies, it is relatively free of pests and disease, doesn’t need pruning, and is tolerant of most soils.

The English holly, Ilex aquifolium, is one of the more difficult hollies to grow.  It doesn’t like it very hot, nor very cold.  It likes well-drained soils, prefers loam or sandy soils, and is hardy to zone 6.  It should grow well along the coast, but in the mountains, maybe not so well.  It’s worth mentioning, though, because during the holidays, you may have seen this shrub sold as a Christmas holly in variegated form. It’s often seen in bunches of cut greens or in wreaths as well, mostly because of its dark, glossy leaves, and the pretty white or yellow margins of the leaves.  Most of the cultivars do get large. The straight species reaches 40’, so be sure if you pick one of these up at the garden center to read the label for the height.

Try these plants in your landscape. Whether native is your “jam,” like it is mine, or introducing a few non-natives to your landscape is your preference, evergreens can be the backbone of the landscape, providing structure and green color through the winter months.  

Author: Mary Ann Ryan, Consumer Horticulture Program Coordinator