We live in the Scarborough Bluffs and have two crabapple trees that have unfortunately died due to blight. They provided shade and visual interest over a backyard patio, and we’d like to plant two new trees in their place. Can you recommend a replacement shade tree variety that is resistant to blight? I had cherry trees in mind due to their beautiful spring show, however we’re not sure if this is a good choice due to the blight.
How fortunate you are to live in as beautiful an area of Toronto as the Scarborough Bluffs. It must have been heartbreaking to loose not one but both of your crabapple trees to blight, likely Erwinia amylovora which is a very serious disease of ornamental species in the Rosaceae family: flowering crabapple, pear, quince, mountain ash to name a few. You will want to stay away from any trees in this family and make sure you have removed all branches, leaves and debris from the infected trees.
An ornamental flowering cherry such as Kwanzan (Prunus x serrulata) will certainly provide you with adequate shade for your patio as well as stunning large double pink flowers for a few weeks in the spring. Brilliant yellow, orange or copper foliage will delight in the fall. It has a spread of 15 – 25 feet at maturity, has a shallow root system, grows in zones 5-9, requires full sun and good drainage. Unfortunately ornamental cherries are often short lived trees. They are more susceptible to diseases and pests than most trees. Black knot, shoot blight, root rots, peach tree borers, scales, powdery mildew, cherry leaf spot can all contribute to poor health and possible demise.
You do have other options. Flowering Dogwood (Cornus kousa) is a small ornamental tree which likes morning sun, afternoon shade, well drained, slightly acidic soil, mulch and regular fertilization. At 15′ – 20′ tall and the same width with dense foliage it is a good specimen tree next to a patio. Long lasting white bracts, red to maroon fall colour and the red berries will be enjoyed by humans and birds alike.
Even more stunning in the spring is the Eastern Redbud (Cercis canandensis). This tree is native to the US. Between March and May its bare stems are covered for 2-3 weeks with light to vibrant pink 1/2”long clusters of flowers which attract bees and butterflies. In fall the leaves turn a strong yellow. It is a wonderful urban tree, 20-30 ft tall with at 25-25‘ spread. It likes well drained soil, full sun to part shade in zones 4 – 9.
A tree that is very resistant to pests and diseases and extremely hardy is the Ivory Silk Lilac (Syringa reticulata ‘ Ivory Silk’). Initially it has an oval or pyramidal shape but it spreads to a more rounded form as it grows older to a height of 20‘ – 30‘ with a 15‘ spread. Large clusters of creamy white flowers last about 2 weeks in late June. This tree likes full sun and well drained soil in hardiness zones 2-9. The City of Toronto has planted many Ivory Silk Lilacs along it streets and boulevards in the past years and all appear to be going strong!
I hope these suggestions will be of interest to you.