Medium height coniferous tree, for Toronto

(Question)

I am thinking about adding a couple of coniferous tree to my back yard for all-year interest and considering “Fat Albert” Colorado spruce, “Taylor Sunburst” pine, “Dragon Eye” pine or Pinus Nigra “Nana”. Are there any pine particular diseases that I should be aware of in our region? Some areas in USA are hit with nematodes, so I am not sure if should invest in pine trees. Not buying Ash tree for sure. Any recommendations among mentioned trees?

(Answer)

Thank you for writing, and lucky for you, embarking on a project of research, and selection, for hopefully this coming spring! The world of conifers is wonderful, rich and varied.

You don’t mention the size of your back yard, but this should be high on your check-list of considerations. Also, generally speaking, wherever we live in the world, the best kinds of trees to plant are our native species, not only because they are adapted to their environment, but they will be culturally integrated with other native life forms. In the Family Pinaceae, the Black spruce  (Picea mariana)  and White spruce (Picea glauca) are among Spruce native to Ontario. That said, there are many non-native, but generally well-suited, conifers that will thrive, and get along well with other regional living creatures.

At first blush, the mention of a Colorado Spruce brings to mind an image of a broad, towering, mature tree — not often the first choice for a medium-to-small, back yard. But, you clearly have done some research, because the Picea pungens ‘Fat Albert’, is exactly that: a semi-dwarf, compact, chunky tree (hence its name) which grows almost as wide as it is tall. Generally, a 10′ tall specimen should be about 8′ wide, with a dense-branching, pyramidal form, and an excellent landscape specimen. Easily grown in average, well-drained soil, in full sun, this is a really superb evergreen choice, with rich blue coloring.  Also, ‘Fat Albert’ is one spruce that really does not require any training, or pruning.

As for your pine considerations, you have suggested species that each feature a unique colour and shape. Your personal preferences can guide you in this regard. The White pine (Pinus strobus) is the provincial tree of Ontario, and the name strobus means cone. When given ample space to grow, the large White pine can be a magnificent addition to your urban canopy. White pine is fast-growing, and presents best in sunny sites, with well-drained acidic soils; it can tolerate some dry soil, but high pH soils might cause yellowing of the needles.

White pine can be susceptible to several native, and introduced, pests and diseases. This includes white pine blister rust, and white pine weevil. Blister rust is caused by a fungus (Cronartium ribicola) that was introduced from Europe in the early 20th century. It can cause yellowing and dying foliage, with entire branches dying, which may be halted by pruning the infected branch.

White pine weevil (Pissodes strobi) is an insect that is native to North America, and causes damage by attacking the leading shoot at the tip of the tree. Once this shoot is destroyed, the tree’s side shoots begin to grow upward, thus creating a forked trunk and a deformed tree.

Regarding your mention of nematodes (multicellular animals that burrow into plant tissue), the pinewood nematode is actually transmitted by pine sawyer beetles, either when the beetles feed on the bark and phloem of tree twigs, or when the female beetles lay eggs in freshly cut timber, or dying trees. The most effective prevention strategy is to avoid planting non-native pines, such as Scots pine, Pinus sylvestris, which was introduced from Europe.

So, again, think native. And think local. And you will likely be making choices that will be for the best suited, and most robust in your area. In closing, below are a few links to hopefully help with your research, and selection !

Ontario’s Tree Atlas: https://www.ontario.ca/environment-and-energy/tree-atlas

You might also want to consult the Toronto Master Gardeners Garden Guide on evergreens for hedges: https://www.torontomastergardeners.ca/index.php/factsheet/evergreens-suitable-for-hedging-a-toronto-master-gardeners-guide/