Philadelphus lewisii 'Blizzard'

Philadelphus lewisii 'Blizzard' mock orange on low water in June 2022 at UC Davis. Photo SK Reid.

Summary

South Coast Research & Extension Center (South Coast REC/SCREC) is located in Irvine California, this site has a sandy loam soil and plants are irrigated with reclaimed water. UC Davis is located in Davis, California, this site has a silty clay loam soil and plants are irrigated with potable water. More information about the field sites is located in the Nuts & Bolts section.

Blizzard is a medium sized deciduous shrub that was included in the trial as a performance benchmark for comparison with Swan Lake mock orange. In the spring, Blizzard produces 4-petaled white flowers. After the petals drop, the green star-shaped sepals persist. Blizzard grew by sending out new shoots from the base that were thicker and longer than the older growth as well as from buds on the old wood. This resulted in a unique, initially uneven appearance at both sites. Blizzard was evaluated at UC Davis and South Coast REC (SCREC) with site specific performance details and recommendations below.

UC Davis Trial – Davis, CA

At this site Blizzard was grown in the full sun. The plants installed were root-bound #1-sized containers requiring some amount of root shaving and/or loosening of the root ball before planting into the native soil. Blizzard is a mock orange cultivar that is not commonly found in our region of California and was included in the trial as a comparison plant for Philadelphus Swan Lake. In our field, Blizzard hovered between acceptable and unacceptable appearance over the course of the deficit season. While we noticed a few flowers in May, June, and October, their appearance on a few of the plants is not enough to outweigh the scruffy appearance of the plants over the summer. We had intended to evaluate this cultivar concurrently in the partial shade field, however, due to scarce availability, we only had enough plants for the full sun field. Statistically there were no differences in overall appearance between the treatments and thus we would recommend irrigating Blizzard on the lowest treatment implemented, 20% or WUCOLS Low in Region 2. However, we would suggest planting this cultivar where it could receive dappled or afternoon shade.

South Coast REC Trial – Irvine, CA

Blizzard was grown in both full sun and under 50% shade cloth. In both exposures, Blizzard was relatively late to leaf out and the initial data was collected in May. Foliage quality and quantity were concerns during the trial. There was some amount of defoliation that was observed throughout the summer. While new leaves were produced in the autumn, foliage quality was low – the leaves exhibited a desiccated appearance. Necrotic spots and edge burn weighed down foliage quality throughout the season. The shade tended to exacerbate the asymmetrical growth habit, resulting in plants with sparse, open canopies. Plants in the shade tended to be more variable in size, and smaller as well, though foliage quality was marginally better. At the Open House, participants seemed to prefer Blizzard when compared to Swan Lake. For both exposures the difference in overall appearance ratings between the 50% treatment and 20% treatment was statistically significant. As a result, we recommend Blizzard be irrigated on Moderate water in Region 3.

Philadelphus lewisii 'Blizzard' mock orange on low water in September 2022. Photo: SK Reid.

Basic Info

Growth and Quality Data

Click Here for Complete Data Set - UC Davis

Click Here for Complete Data Set - SCREC Sun

Click Here for Complete Data Set - SCREC 50% Shade

Philadelphus lewisii 'Blizzard' mock orange on moderate water in May 2022 at South Coast REC.

Philadelphus lewisii 'Blizzard' mock orange on moderate water in October 2022 at South Coast REC.