UMASS Landscaping update

General Conditions:

Late summer is flourishing across the Pioneer Valley as the autumn season unofficially starts following the Labor Day weekend. We’ve had some downright pleasant temperatures in recent days with highs in the upper 70s to low 80s and cool nights in the 50s. The oppressive heat and mugginess of mid-summer is in the past and the landscape is still vibrant with color. For many trees and shrubs, this has been a banner growing season with the (over) abundance of rain. New shoot and leaf development was recently observed on eastern hemlock, eastern larch, pin oak, redbud, and red maple across the UMass campus. When deciduous trees are still flushing new growth in mid-August, it’s been a good year. Conifers like false-cypress, arborvitae, and juniper often have a late season flush and this year it’s far more noticeable. Turfgrasses and lawn weeds are still growing at a rapid pace and remain healthy and green. Early leaf color and drop is also occurring on scattered trees across the landscape. September conditions will play a significant role in the quality of the fall foliage. Bright, sunny days and cool nights during our ninth month help to stimulate production of anthocyanins that produce brilliant reds and expose the carotenoids that produce the oranges and yellows as chlorophyll production wanes. Soil moisture remains plentiful and late August through early September is an excellent time to transplant conifers. New root development in the fall will help them better establish the following growing season. The appearance of red maple seedlings has finally slowed down after what was undeniably a mast year for this species. Many sugar maple canopies are loaded with mature seed that will soon be falling. This is a good time of year to gently excavate the root flare on young trees that were transplanted within the past five years (or so) to prune out any adventitious roots that may be problematic over time. With the abundance of rain this season, mulch and other organic matter may have washed over the root flare, allowing for the development of future circling and girdling roots. Groundcovers or perennials established at the base of the tree can also result in the flare being covered. The nighttime soundscape remains very active with katydids and crickets. 

Pests/Problems:

Apple and crabapple defoliation due to apple scab continues with some trees nearly defoliated. Pseudocercospora leaf blotch is widespread on lilacs (Syringa vulgaris) throughout the area. Infected plants have brown-colored spots and blotches that can advance to a blight of the foliage and premature shedding (see Disease section below). Lilacs are extremely hardy plants and these infections will likely result in only minor reductions in growth and/or flowering next season. However, remove and discard infected foliage from the base of the plants this autumn season to reduce overwintering inoculum. The abundance of rainfall this season is likely to blame for this significant outbreak. Slime molds and mulch-inhabiting fungi have been very common this season. Slime mold growth around the base of trees and shrubs can be alarming for some but these organisms do not parasitize plants. Tubakia leaf blotch is very conspicuous on scattered oaks in the landscape right now. Infections often take place in the spring but symptoms appear much later in the growing season. Currently, it appears as reddish-brown circular spots that coalesce to create larger, necrotic blotches. The disease is primarily a concern for members of the red oak group but white oaks are also susceptible. Scattered feeding damage by grasshoppers is present on hardwoods and conifers. Slugs are still very abundant on leafy perennials. It’s not too late to treat lace bug infestations on azalea, rhododendron, and Andromeda.