Photo: Contributed This screen shot of the Okanagan Xeriscape Association's plant database on its website, shows one of the new additions to the trees category, now considered a good choice for this valley, in consideration of climate change. After the hardscape part of your landscaping, which can include pathways, patios, retaining walls and water features, your most expensive purchase will be for trees in your landscaping. With the past two years of extremely erratic weather, we have to reconsider our traditional tree choices and embrace other options.
It is vital that we choose trees adapted to our climate in the Okanagan and that are both drought and heat tolerant, as well as able to survive temperature swings of a staggering 70 F. Trees which we have traditionally selected are now suffering under these new climactic conditions and are therefore more susceptible to pests and disease. One example which has been traditionally used in street and residential plantings is the London Plane tree, (Platanus x acerifolia), which is now frequently infected with anthracnose at sites throughout this region.
This foliar disease causes bud damage, wilted leaves and substantial defoliation. Although not fatal, it certainly creates an unsightly and weakened tree. Historically, we planted lots of ash trees (Fraxinus spp) in urban areas but this species is susceptible to the Agrilus planipennis, or emerald ash borer.
Emerald ash borer originated in Asia, so it has few native predators to control it here and has decimated millions of ash trees in North America since its arrival in the 1990s. It is estimated 99% of all ash trees were killed within eight to 10 years of the beetle’s arrival in North America. This spring, emerald ash borer was detected in B.
C. for the first time. It is only a matter of time before this pest arrives in the Okanagan Valley.
I recently heard a statistic that a city-planted tree has a life expectancy of just 12 years. We need to do a better job of caring for our individual trees and our tree canopy in general, as our survival is tied to theirs. I regularly travel up Clifton Road and have recently seen the aforementioned London Planes planted under three-phase power lines.
What are we doing? The London Plane trees will reach a height of 70 to 100 feet tall, at which point a contractor will be hired to sever a good portion of the tree away from the lines, resulting in a weakened and ugly tree. I understand we have made this mistake in the past but why are we continuing to do so? Check out the Okanagan Xeriscape Association plant database at www.okanaganxeriscape.
org to see some of the recent additions to the list of trees we have researched and trialed, and which we believe will be able to thrive in our new, challenging conditions. One of the new additions to the tree database is the Deodara cedar (Cedrus deodara). Do not confuse this true cedar with the genus Thuja, known commonly as hedging or pyramid cedars, which I often warn are completely inappropriate for the Okanagan climate due to their high water requirements.
Deodara cedar is a beautiful evergreen which has a similar shape to spruce with graceful, pendulous branches. It is native to Afghanistan. This evergreen can be considered as an alternative to blue spruce as it is significantly more drought-tolerant.
Some of the most cold-hardy cultivars include "Sanders Blue" and "Shalimar." For those who are impatient for their evergreens to grow, note the Deodara cedar will put on up to two feet of growth per year when young. That rate slows as the tree matures.
It reaches an ultimate height of up to 70 feet, with a spread of 20 feet. Another tree, not yet planted extensively in the valley but deserving to be so, is Osage Orange (Maclura pomifera). It is a medium-sized deciduous tree, reaching 35 to 60 feet tall and wide.
It is hardy in Zones 4 to 9. This tree is easily grown in average soil in either full or part sun and is tolerant of poor soil, drought, cold, heat and windy sites. Historically it was planted in hedgerows to serve as fencing and it is useful in challenging areas where other woody ornamentals may struggle.
The cultivar "White Shield" is both thornless and fruitless, with a broadly rounded crown and beautiful shiny leaves turning golden-yellow in the fall. Wichita is another excellent vigorous cultivar. Browsing deer do not favour Osage Orange.
Make Water Work As in years past, the Make Water Work challenge encourages homeowners to take the pledge to make water work smarter on their landscapes. By heading to the website at www.makewaterwork.
ca and pledging, for instance, to choose plants suitable to our dry environment, you will become eligible to win one of two prizes of $500. The pledge encourages you to make better choices about your consumption so there will be enough water for firefighting, aquatic health, and agriculture in our valley. The Okanagan Xeriscape Association is grateful for the ongoing financial support of the Okanagan Basin Water Board and is proud to be collaborating with them on their Make Water Work campaign.
Sigrie Kendrick is a master gardener and executive-director of the non-profit Okanagan Xeriscape Association. This article is written by or on behalf of an outsourced columnist and does not necessarily reflect the views of Castanet..
