September 15, 2012
By Jen Llewellyn
OMAFRA nursery crops specialist

Everyone and his dog is talking about the weather this summer.

I too want to talk about the weather, and how it created some of the challenges we are seeing with ornamental plants.

This has been an extremely tough year to be a farmer. We had one of the mildest and driest winters on record. The growing season started several weeks early with a lot of heat and very little precipitation. Several container crops broke dormancy early and producers had little choice but to vent and/or pull off poly in March and start irrigating.

These early-breaking crops sustained a lot of low temperature injury in April and May, and in the case of evergreens, many of these crops were not able to recover and will remain in production a year longer to make up for it.

The pome fruit and tender fruit industry lost a lot of blossoms on its early-blooming varieties to low temperature injury, which significantly reduced yields across the province.

Freeze-thaw injury and foliar desiccation on conifers was also unprecedented. In particular, eastern white cedar in the field and landscape suffered major frost cracks this winter. Look for large, oblong splits in the bark on the trunk. The resulting shoot dieback was reported across Ontario this summer. Many trees had to be pruned and very young trees had to be replaced.  

The dry parts of the province, especially those areas with soils that have low water holding capacity (sand or clay) are particularly stressed. This includes, but is not limited to, the Niagara region, Haldimand Norfolk, parts of Elgin and Middlesex, Grey, Bruce, north Wellington and Waterloo, Timiskaming and parts of central and eastern Ontario, including Renfrew.

Virtually all agricultural industries have been impacted directly or indirectly. Many producers will see some aid through their enrolment in the Agri-Stability program.  

Varying amounts of precipitation in the last month or so have been a welcome relief, but in some cases it was too little, too late. As of Aug. 1, there were 13 watersheds or sub-watersheds with confirmed Level II low water conditions. Level II indicates a potentially serious problem and requests producers with Permits to Take Water to voluntarily reduce their use of water by 20 per cent.

We have seen a tremendous number of stress symptoms in the landscape and the nursery. Conifers that were transplanted in the last year are or so were particularly susceptible. We have seen needle tip browning, needle browning and needle drop on several evergreens, including fir, spruce, pine and hemlock.

Needle drop was something we saw on Colorado spruce last summer and it’s only become worse. The amount of emails and calls I’ve received about dieback on recently-planted trees is pretty significant.  The scary part is that many landscapers and homeowners said that they either were not irrigating or (even worse) they had been irrigating every one to two days. Couple this with heavy clay, poorly-drained soils and you have a recipe for root dieback, or root rot.  

Landscape specimens that are faring well are those that received a long, slow irrigation every seven to ten days. You can help woody plants recover by continuing to irrigate the root zone into September and October while soil conditions remain dry. Remember, roots of trees and shrubs extend well beyond the dripline of the canopy, so make sure you are also watering the area surrounding the canopy. The idea is to aim for 20 to 25 mm with each irrigation event, which you can measure with a rain gauge or by setting out a tray.

Hold off fertilizing until October to let soils cool and recover their moisture. The fall root growth period is a great opportunity for nitrogen and potassium uptake of woody plants.
Jennifer Llewellyn may be contacted at the Bovey Building, University of Guelph, at 519-824-4120, ext. 52671, or Watch for the Nursery-Landscape Report on