I have built flower boxes, using stone, that follow the steps at grade leading to my backyard at the side of my house. I have 5 flower boxes in all.
The first two are 3.5 x 3.5 feet square.
The last three are 4.5 x 4.5 feet square.
This follows the fence line where I would have between 2 feet from the flower box to the fence at the top and 3 feet from the flower box to the fence at the bottom.
What type of columnar tree could I plant that would work for that space?
I don’t believe I could have one that grows any wider than 6 feet and I’m struggling with what to put there.
Deciduous and evergreen trees provide us with clean air, buffering from strong winds, shade from the heat of the day, as well as habitats for birds and smaller mammals.
Not knowing whether you prefer a deciduous or evergreen tree, your soil conditions or sun exposure it is difficult to make specific recommendation.
You may wish to consider the following deciduous trees:
Pyramidal Beech (Fagus sylvatica ‘Fastigata’) A tall, extremely narrow slow growing tree which requires rich soil and significant moisture.
Serviceberry (Amelanchier canadensis) can be found as a tree or shrub. This tree/shrub provides year round interest, white flowers in spring, blue-black fruit in summer, and brilliant fall foliage. Grows 5m- 8m tall.
Eastern Redbud(Cercis canadensis) The tree develops flower buds along older branches right up to last years branch growth. The clustered flowers are pink and are compared in shape to pea or bean flowers. Flowers develop first and branch and leaf growth starts to develop at the end of flowering. The leaves are heart-shaped with a smooth edge. Grows 5m x 6m. There are other smaller weeping varieties which are also interesting. Check out lavender twist weeping redbud.
Cherokee Chief Dogwood (Cornus florida). New leaves emerge bronze-red in spring, maturing to green. Autumn brings fantastic burgundy-red foliage. The show continues into winter, with red fruit clinging to bare branches. You may also wish to check out Kousa Dogwood (Cornus kousa).
If you are interested in evergreens you may wish to consider the following genera:
Pyramidal yews (Taxus capitata) , Columnar Yew (Taxus citation), Irish Yew (Taxus baccata ‘Fastigiata’). All these yews require well drained soil and grow best in sun/part shade conditions.
If you have full sun then Degroot’s Spire Cedar (Thuja occidentalis ‘Degroot’s Spire‘) would be an excellent choice.
I would also recommend browsing your local garden center for additional examples. Once you see a tree that strikes your fancy remember to check the height and spread at maturity. The tree might look small now but they will grow. Make sure to select a tree that will grow within your environmental conditions (amount of sunlight & soil conditions). Remember, right plant for right place will lead to success.