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  • Spaeth Property Service

Seasonal Update from UMASS Amherst Extension about landscaping conditions

Landscape Message: April 21, 2023

General Conditions: The spring season has rocketed forward in the Pioneer Valley since our last report. A five-day span of bright sun and progressively warming temperatures saw us climb from 69°F (4/10) to a staggering 93°F (4/14). Both 4/13 and 4/14 were unbearably hot for mid-April, especially with the lack of shade from deciduous trees, and new record high daily temperatures were established in Springfield. Red flag warnings, indicating ideal conditions for wildfire development, were hoisted several times due to low humidity and strong winds. An air quality alert was also enacted on 4/14 as ozone reached levels that could affect sensitive groups. Nighttime low temperatures in the 50s during this unseasonably warm span liberated plants from the cold that often constrains growth this time of year. As a result, a wide array of trees and shrubs are now leafing out, including witch hazel, Japanese maple, redbud, crabapple, viburnum, stewartia, katsura, serviceberry and privet. Mid-April is a tenuous time for leaf out and low temperatures dipping close to freezing on 4/19 and 4/20 were concerning. A report from the UMass Cold Spring Orchard predicts apple and pear blooming will begin around 4/22, after the latest round of warm weather. On the coniferous side, arborvitae, false-cypress, juniper and ginkgo are putting on new growth. Pine candles are elongating and hemlock and yew buds are swelling. The first half of April was also quite dry, with no measurable precipitation from 4/2 to 4/15. Highly scattered showers from 4/15 through 4/18 produced only minimal accumulations (<0.5”), but cooler temperatures and the light drizzle provided some relief and stimulated more flowering. In some locations, the uppermost soil horizon is drying out but there is still plentiful soil moisture in deeper horizons. Sugar maple, Norway maple and various birch species have been in full flower, producing a significant percentage of pollen in the air. Turfgrasses have quickly transformed from dormant brown to a lush, vibrant green. The soundscape is increasingly active with the mating calls of peepers and tree frogs along with a variety of migratory birds. A variety of bees, fireflies, lady beetles, hover flies and other beneficial or benign insects are also abundant now in the landscape.

Pests/Problems: As we continue to assess winter injury on trees and shrubs, Weeping Higan cherry (Prunus x subhirtella 'Pendula') are not flowering and this is very troubling. A large and old specimen with a broad canopy on the UMass campus should be in peak bloom right now but has no flowers. Additional specimens around Hampshire County also show no activity. The early February arctic freeze is the most likely culprit for the injury. The ubiquitous Snow Fountain cherry (Prunus 'Snofozam') has flowered normally throughout the area. Some trees appeared thin but they can be so badly pruned it’s hard to assess health in some cases. It also appears some Forsythia were injured by the freeze as well. Weak flowering has been observed on various plants and drought may have also been a factor. Aside from certain flowering cherries and scattered forsythias, it appears many plants are largely unscathed after the winter season. Exceptions exist, of course, with some plants (e.g. American holly, rhododendron and redbud) exhibiting symptoms of desiccation and freeze injury. It’s still too early to determine how rhododendron and azalea flowering was affected by the cold. PJM rhododendrons are flowering normally, but these cultivars are extremely cold hardy. Snowball aphid activity on viburnum will be evident soon as new growth develops. Damage is usually minor and plants grow out of the injury. Viburnums may also have blighted shoot tips with peeling bark, often the result of winter injury. This is common for these plants and they should be pruned out as soon as possible. There are a variety of small green caterpillars that chew and roll leaves early in the season. Bruce spanworm (Operophtera bruceata), a native pest of forest and landscape trees, and the redbanded leafroller (Argyrotaenia velutinana) are examples. Close examination of developing leaves on younger and accessible trees is necessary to observe feeding injury. Hand picking/crushing is sufficient on smaller trees. Orange spore masses produced by rust pathogens (Gymnosporangium spp.) will soon be developing on Juniperus. When especially numerous, they can be pruned out and discarded. Several azaleas and rhododendrons with suspected iron deficiency were observed. Symptoms include interveinal chlorosis on the foliage (particularly the newest foliage), stunted growth and canopy dieback. Reducing soil pH, with sulfur for example, can help to correct the issue. Continue to prune out dead twigs and branches while they are most visible. Mosquitoes, black flies and paper wasps have emerged. Garden weeds are quickly developing along with invasive plants like honeysuckle and Oriental bittersweet.

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