Trees For Tight Places

Any landscape is predicated on a finite amount of space.  A property could be described by a certain amount of square footage on the ground plane.  A landscape is comprised of lots of different elements, the largest of which would be the sky.  Next up, the trees.   I suppose a small urban property could be forested like woodland, but that assumes  the gardener has only one use in mind for their landscape.  Fortunately, trees come in all sizes and shapes.  A number of trees have a fastigiate, or columnar form.  This means just what the word implies.  The foliage or needles grow naturally in a column.  A tree with a restricted spread is a great choice for small gardens, for gardens that ask for screening, and for gardens asking for natural ornament.  Years ago, this side garden was in full view of a neighboring house.  Today all that remains of that view is a chimney.  The arrangement of pairs of columnar hornbeams have created a natural pergola that is home to a shady seating area.   

My first visit to this property immediately brought the idea of columnar trees to mind.  The back yard is very small, and adjacent properties very close.  The prominent feature of the yard-a beautifully constructed wall.  The soil had been mounded up against the wall, and boxwood had been planted against its base.  In the front of the bed, a collection of perennials. The boxwood and perennials obscured rather than featured the wall,  nor could they possibly provide screening from a neighboring house. The rear yard screen of hemlocks had grown thin, and was very wide at the bottom where no screening was really needed.

These columnar Bowhall maples will eventually completely screen the neighbor’s garage wall from view.  Lowering the grade meant much more of the wall was available to view. The hemlocks were replaced with Thuja Nigra, an arborvitae that grows narrow and tall.  A very small yard is now completely private, given the planting of  fastigiate trees.  The maples only occupy the air space; their pole-like trunks take up no room whatsoever.  The arborvitae are narrow at the bottom as well as the top.  This helps to make a very small space feel spacious. 

This back yard sloped steeply towards the foundation of the house; water in the basement was a problem.  A retaining wall permitted the soil at ground level to be graded away from the house.  The top of the wall was planted with hornbeams  spaced at 12 feet apart; they will grow together faster than you think.  Carpinus fastigiata is naturally broadly egg shaped, but it is quite tolerant of pruning.  The hydrangeas will make the wait for the trees to grow a little more tolerable.  It will be interesting to see what direction the client wants to take with pruning.  They have time to sort that out. The wall also gave the trees a little leg up, screening out the neighboring property.

Arborvitae have a naturally columnar shape, but they also adapt quite well to closer pruning.  This landscape called for a vertical element which would not shade the surrounding plants.  A once yearly pruning is all it needs to keep it in shape.

This landscape features both pruned and unpruned arborvitae.  The pruned cylindrical shapes are very interesting and sculptural.  Pruning any tree or evergreen should be undertaken over time.  It has taken my palabin lilacs on standard 2 years to recover from the shock of my pollarding fit. 

There are those trees that are not particularly columnar by nature, but they are amenable to pruning.  The hybrid magnolia “Ivory Chalice”, a cross between magnolia acuminata, and Magnolia denudata, has been priuned to stay within the confines of this very narrow space along a driveway.  They have been happy here for over 10 years.

Populus tremuloides erecta , or Swedish columnar poplar, is a loosely growing columnar tree that will eventually provide some screening for the giant windows of this contemporary home. The rounded and scalloped leaves flutter in the breeze just like any other popple, and the fall color is great.  This tree may occasionaly have a branch that falls out-a little pruning will put that to right.  Even older trees are not much wider than 5 or 6 feet.

Of course the queen bee of columnar trees has to be the fastigiate European green beech.  Properly cared for, as these are, they make a very strong vertical statement. 

Once these trees reach the roof line of the house, they could be pruned flat.  Age will only improve these fine trees.

Some Thoughts on Spacing

Once there is a landscape plan in place, there is the matter of the plant count.  Determining a plant count has much to do with spacing.  I have read much about rules for spacing plants properly for optimal growth, but the issue is more complex than that.  For instance, if I am planting pachysandra, and space them at a foot apart, I need one plant per square foot.  For 500 square feet, I will need 500 plants, or about 10 48 count flats.  If I space them at 6″ apart, I need 4 plants per square foot, or 2000 plants, or about 40 48 count flats.  Option A asks for a modest up front investment, but I see a lot of time ahead devoted to weeding, the purchase and spreading of a lot of mulch, and a lot of water thrown on bare ground.  I also see a grim looking space for probably 3 years.  My solution?  Start a groundcover bed small and plant densely.   Enlarge it next year, or the following season- only that number of square feet you can plant densely.  My mature, healthy beds of pachysandra-individual plants are much less than an inch apart.

Spacing evergreens has everything to do with the desired outcome.  Should I plant a taxus densiformis in the middle of the lawn, and give it 50 years to grow, I will have a single plant of considerable size.  A hedge, or a mass of yews is more about a community. Sometimes I look at the distance between the rootballs.  The big idea here-everybody has their own subterranean digs. This may mean that the foliage touches.   

Plants are much more sociable than I.  I want my space. I was never so conscious of the need for my own space than after my knee replacement.  I was less than stable on my feet, and was not interested in an enthusiastic Golden Retriever broaching my borders. But plenty of plants do well planted in close quarters.  They are completely happy to relinquish their individuality, and become a part of a larger community.

One of my most favorite landscape moments-the arrival of the plants.  These 1.5″ caliper fastigiate hornbeams in 25 gallon pots would be planted as if they were the poles of a pergola. Carpinus betulus “Frans Fontaine” is a culitvar of fastigiate hornbeam which is slower and more densely growing than the species.  Even so, it will grow 30′-35′ tall, and 15′-18′ wide. I spaced them at 8′ on center, knowing they would grow together.  Someday there would be a green roof under which there would be shade.   

I had other reasons which influenced my spacing.  The house next door loomed over this side yard property.  Evergreens would have provided year round screening, but they occupy a lot of space at the ground plane.  My clients wanted to entertain in this space.  Given enough time, and spaced close together, they would eliminate this view of the neighbor.   

Carpinus are also very tolerant of pruning.  Decisions about spacing are specific to the species in question.  The vast majority of green spaces have not been planted by a person.  There are those wild places densely populated by plants.  No natural forest or meadow is at equilibrium; some plants are coming on as others are in eclipse.  Perhaps a lighting strike will “prune” a giant tree such that new plants can take hold around it.  Should you be interested in the exceptions to any gardening rule, visit any wild and untended space. 

Five years later, the new yews have grown together to make a mass.  The topmost row of yews had been transplanted from the front of the house; the new yews will eventually cover their bare lower limbs.  It sometimes makes more sense to underplant an old and ungainly shrub rather than tear it out.  These big old yews will eventually become part of a simple mass.Eight years later, the house next door has all but disappeared. As the carpinus grow taller, they can be selectively pruned on the underside to permit easy passage beneath them. 

The yews planted behind the carpinus are planted on a gentle slope that rises to the neighboring driveway. Though the shade has become considerable, they are green and well needled from top to bottom.  Allowing those densiformis yews to keep their natural shape is in large part responsible for their continuing health.  Yews do not respond so well to hard formal pruning.  Once all light is blocked to the interior of the shrub by a proliferation of growth on the exterior, those inner branches will go bare.  I have begun planting Taxus media Moonii in place of Hicks yews, as their natural growth is much more upright and formal. 

This is a great spot to sit.