Hort Notes 2025 Vol. 36:2

A monthly e-newsletter from UMass Extension for landscapers, arborists, and other Green Industry professionals, including monthly tips for home gardeners.

Click on the headings below to jump to that section of the newsletter.

Announcements

Save the Dates

Landscape Pests and Problems Walkabout: June 24th

Pollinator Steward Program Summer Cohort: June Registration

Turf Field Day: July 23rd

Invasive Insect Certification Program: September

UMass Extension is Hiring! 

Educator II, Sustainable Turf & Landscapes 

UMass Extension is hiring an Extension Educator II for Sustainable Turf & Landscapes. This position will support development and implementation of educational resources and programming and participate in delivery of research-based information to meet stakeholder needs. This is a full-time position with the opportunity for a hybrid work schedule. The successful candidate will have achieved at least a bachelor’s degree and have two years of relevant professional experience. Click to read more and apply.

Photo Contest for the 2026 UMass Garden Calendar

Ever take a great garden photo and think “this would be perfect for the UMass Garden Calendar?” UMass is accepting photos from the public through April 4th for possible use in the 2026 Garden Calendar!

Photos must be horizontally oriented with high resolution and feature garden plants of particular horticultural interest. Winning photographers will be credited in the Garden Calendar and have an opportunity to write a caption about the plant. They will receive 5 free calendars. Visit out website for complete info and submission instructions.

Hot Topic

Eastern MA Joins the Periodical Cicada Magic!

Our very own Magicicada septendecim, a species of 17-year periodical cicada, is emerging in parts of Barnstable and perhaps Plymouth counties this year, after spending the last 17 years beneath the ground!

Ideas for Observing

• Periodical cicada nymphs will emerge from the ground in approximately late-May and early June. Research shows that periodical cicadas emerge when soil temperatures at a depth of 7-8 inches reach approximately 64°F (Heath, 1968). You can track soil temperatures for Barnstable county by visiting this website.
• Not sure what to look for? Visit this resource from the University of Connecticut: images of nymphs emerging and adult periodical cicadas.
• Where are the periodical cicadas? This map shows historical sampling of periodical cicadas in Massachusetts and beyond. Check to see if your area is on this map. If it is, talk to local garden centers, master gardeners, tree care professionals, or Extension to learn more about where you might find these special insects. While they may be in your area, local abundance varies significantly by site. Barnstable County Cooperative Extension and Plymouth County Extension are also available for information about periodical cicadas and much more!
• Not in an area on the map? Not to worry! This could be an opportunity to engage in entomotourism – wildlife, specifically insect or other arthropod, focused sight-seeing! This entomologist knows of at least one nursery in East Falmouth, MA that is planning to celebrate periodical cicadas – including dressing up as one!
• Take photos and report your location! Periodical cicadas are incredible native insects that benefit our ecosystems. Their populations have been threatened, and researchers want to know where they are. Join the MA Department of Agricultural Resources in tracking periodical cicadas in eastern MA by reporting your observations through iNaturalist! Other researchers will receive alerts when you report sightings here.

Tips for Preparing

Here are some things to consider before the periodical cicadas emerge, if you are lucky enough to live or work in an area experiencing this incredible natural phenomenon. These steps are not necessary if periodical cicadas are not expected to emerge near you:

• Wait until the fall to plant new apple trees or other susceptible hosts. Particularly for orchards, this spring may not be the time to plant young trees in periodical cicada emergence areas. Waiting till fall (or next spring) will give them time to lay their eggs on mature trees that can handle ovipositioning (egg laying). On certain mature trees, egg laying naturally prunes branches and overall has been shown to benefit trees (Dr. Zoe Getman-Pickering, personal communication). On young trees, however, this activity can be a significant stressor.
• If you must plant a young tree, install a physical barrier. On newly planted host trees or existing smaller caliper trees, bird or other similar netting with opening sizes less than ½ inch can be placed over the entire tree to prevent periodical cicadas from accessing them. This must be done in advance of periodical cicada emergence and subsequent egg laying, typically ahead of late May (see prior comments about timing and tracking).
• Learn more about periodical cicadas. Understanding what you might expect while these insects are in your area might help reduce the shock of sharing your environment with them. For example, adults are approximately 1-2 inches long, they make noise as heard in the recordings available from the University of Connecticut, and in patchy areas of Barnstable and Plymouth counties, past research shows that 1 million cicadas per acre is possible to expect. Will that be the case in 2025 for MA? We cannot be certain. The important thing to remember is that we’re surrounded by similar numbers of insects all the time, and due to their smaller size, we may never notice them. Check out the further resources below for more information!

Periodical Cicadas are Not a Plague

• They do not bite or sting.
• They are not poisonous or toxic.
• They will not harm people, their pets, or their home. Although note that periodical cicadas are known bioaccumulators of mercury, so the safety of ingesting them is questionable. They may, for other reasons, also make pets who feed on them sick. Seek veterinary assistance if this becomes a concern.
• The ecosystem-wide resource pulse they provide to our food webs produces change! The 2021 Brood X emergence was shown to cause 80 bird species to switch their feeding to periodical cicadas, leaving herbivorous insects like caterpillars out of their diet for a short period of time. Caterpillar populations were essentially doubled! While this will increase caterpillar feeding on oak leaves, this phenomenon is short lived. The addition of nutrients from decomposing cicadas can alter foliar nitrogen content, nutrient use efficiency, plant biomass, and patterns of herbivory in herbaceous plants (Getman-Pickering et al., 2023).

Further Resources

Map of Brood XIV (14) from the University of Connecticut

Periodical Cicada Fact Sheet from UMass Extension

Periodical cicadas disrupt trophic dynamics through community- level shifts in avian foraging

Report Periodical Cicadas in Eastern MA on MDAR’s Project through iNaturalist

University of Connecticut’s Periodical Cicada Information Pages

Tawny Simisky, UMass Extension Entomologist

Trouble Maker of the Month

Winter Injury on Evergreen Shrubs

The winter of ‘24–’25 proved to be very damaging to rhododendrons and hollies throughout the region. While not as widespread, boxwood also suffered significant damage in some locations.

Freeze and desiccation during the winter months is a common injury for many evergreen shrubs across managed landscapes in southern New England. Plants most frequently affected include rhododendron / azalea (Rhododendron), holly (Ilex), mountain laurel (Kalmia), andromeda (Pieris), and boxwood (Buxus). Among the plants listed here, there is significant variation in cold hardiness by species, variety, and cultivar, with some cultivars exhibiting extreme cold hardiness (e.g. Rhododendron 'P.J.M').

Symptoms: Winter injury on evergreen shrubs can manifest in several ways and usually becomes visible in late February through March. For rhododendron, leaves that naturally curl during the winter do not unfurl in the spring and become wilted and desiccated with a pale green to tan coloration. Twigs and branches may also exhibit wrinkled bark, and the vascular tissue appears pale green to brown when the bark is shaved. Azaleas, hollies and andromedas can develop pale green to brown, scorched leaf margins or leaves that are entirely brown. Rhododendrons, azaleas and hollies may also have dark brown to purple blotches across large portions of the leaf midrib or margins. On boxwood, entire shoots often appear bronze to tan in color. In some cases, plants are killed outright but many survive and experience scattered branch dieback.

Extreme cold temperatures combined with strong winds, especially in exposed settings, often lead to winter injury on evergreen shrubs. Even when temperatures are not lethal by themselves, strong winds desiccate the foliage. There may be a distinct demarcation between healthy lower canopy branches and injured upper canopy branches that coincides with the height of the snowpack. Drought stress during the autumn season is a major predisposing stress that can disrupt or delay cold acclimation, making plants more susceptible to freeze damage. However, even plants under regular irrigation can experience winter injury.

Management: In many cases, a patient and prudent approach to rehabilitation is required to understand the full extent of the injury. For example, rhododendrons with serious foliar injury may have intact shoots that will flush new foliage. Therefore, pruning should commence only when it's clear that twigs and branches are dead. Once it is clear which plant parts have survived and which are dead, pruning to remove the dead canopy parts (individual leaves or entire shoots and branches) should commence. If these dead parts are left in the canopy, they can be colonized by opportunistic pathogens that may further expand the dieback (e.g. Phomopsis and Botryosphaeria). In some cases, these fungi are already present within the plant as endophytes (pathogens living within a plant but causing no noticeable symptoms until the plant becomes stressed or injured). Phyllosticta and Pestalotiopsis are fungi often associated with winter injury on rhododendron and holly. After this initial sanitation prune, selective pruning may be required during the growing season to remove additional dieback.

If the shrubs are well-established and in evenly moist, well-drained soils, supplemental watering is not necessary unless we experience a prolonged drought. For plants in exposed settings or in excessively drained, sandy soils where drought stress is a problem, provide supplemental water on a regular interval during prolonged dry periods. Newly transplanted shrubs should receive supplemental water until established. Fertilization may help to restore vigor to badly injured plants but can reduce flowering the following year for certain plants (e.g. rhododendron).

Nicholas J. Brazee, UMass Extension Plant Pathologist

Q&A 

Q. I am a service provider/grounds manager/homeowner/etc. eager to get out and fertilize lawns this spring… when should I start?

A. Generally, fertility for a turf system is about providing supplemental nutrients that are not otherwise available to the plants in amounts sufficient to achieve the desired level of performance. Optimal nutrition, meaning nutrient levels that support plant needs, but are not excessive, will help in the production and maintenance of surfaces that meet expectations in terms of both appearance and function. Supplying enough, yet “just enough”, will also help to prevent adverse environmental impacts from nutrients, especially nitrogen (N) and phosphorus (P), which can become pollutants when they move beyond the turf system.

Being attentive to nutrient sources and rates to achieve “just enough” may not be adequate, however, if the timing is off. A first step in fertility is putting nutrients into the root zone in a plant-available form. Once there, at least two more things are needed for nutrients to move from the soil into the plant: ample moisture, and root activity. It’s important to understand that, even when fully active, plant roots are not able to capture nutrients like N & P directly. Instead, these nutrients move into the root along with the uptake of water, literally hitching a ride in what’s called the transpiration stream. Transpiration refers to the water that moves from the soil, into the root, and around and throughout the plant, prior to being exhausted to the atmosphere through leaf pores (stomata). Assuming that there is ample water in the root zone to serve transpiration needs, the next most important component is plant and root activity. The more active and vigorous that the plant system is, the more robust the potential for transpiration, and therefore water and nutrient capture, will be.

Free nutrients in the soil water (often called the soil “solution), while readily plant-available, are also subject to possible loss. Water and nutrients not captured by plants can move downward through the soil profile and out of the reach of plant roots in a process called leaching. Nutrients that move in this way do not benefit plants as intended, and so this is wasteful of material, time, budget, and labor resources. More broadly, nutrients lost to the larger environment can negatively impact natural systems and resources. Among the most immediate potential impacts of nutrients lost via leaching, for example, is contamination of groundwater resources.

Leaching, unfortunately, is not the only concern for loss and the associated risks. One of the realities of fertilizing established turf is that materials must be applied to the surface, on account of the lack of opportunity to incorporate them into the soil. This means that it takes some time for nutrients and nutrient-containing materials to move into the root zone where they become plant-available. Until then, they are vulnerable to another major route of potential loss: runoff. Runoff happens when water input from heavy rain or irrigation accumulates sufficiently and begins to move downslope. Runoff can very easily and readily carry nutrients, organic materials, and soil out of the system and into the environment, especially surface water, which makes runoff another possible source of pollution.

An important functional service of turf is the mitigation of runoff and stormwater… the thick plant canopy serves to slow the momentum of runoff, thereby promoting desirable infiltration into the soil. Turf that is dense and growing vigorously, therefore, is most effective for managing nutrient losses from runoff. On the other side of the coin, the mitigation capacity of inactive, dormant turf is significantly reduced.

With all of the above said, what is the key for preventing leaching and runoff from stealing applied nutrients and resulting in possible environmental harm? Aligning the presence of high levels of plant-available nutrients in the system (i.e. fertilization) with the times that the plant is growing most vigorously. On the specific question of when to fertilize in the spring, this means withholding fertilization until the plant is active and fully capable of taking advantage of those nutrient inputs. Conditions and the pace of plant development vary from season to season, so specific trigger points, like calendar dates, are unrealistic. Note, especially, that Massachusetts plant nutrient regulations prohibit nutrient applications to “frozen and/or snow-covered soil”, as well as to “drought dormant, cold dormant, inactive or otherwise brown turf.” The current guideline is to refrain from spring fertilization until at least “50% green-up”, or in other words, the point at which the departure from winter dormancy is well underway and the turf is at least halfway to normal expected seasonal color and vigor (Figures 1&2). This simple step will help to ensure optimal utilization of applied nutrients, and minimize risks for loss, waste, and pollution.

Q. In a recent Hort Notes, you answered a question about optimizing mowing practices. I’m especially interested in reducing mowing time… do you have any additional tips on that front?

A. I devoted appreciable space in that article to increasing mowing efficiency through turfgrass selection, so I’ll assume that the reader is referring to equipment considerations. With that said, research continues around reducing mowing demands via selection and genetics… for example, check out this recent work with Kentucky bluegrass.

There are many with more expertise than myself on the equipment front, and the technology moves fast, but I do see and hear a lot in my travels. Here are some thoughts:

Time is an important resource spent in managing turf. Mowing, the most fundamental of management practices, demands an outsize portion of time for most programs. Reducing mowing time frees space for other activities and enables greater efficiency and revenue potential for service providers. Some of the key parameters to look at when selecting equipment to reduce mowing time are cutting width, turning capacity, and ground speed capability.

A larger machine with a wider deck or reel size is among the primary options available to cover more ground. Possible drawbacks that should be considered include reduced maneuverability, heavier weight, transport considerations (if applicable), storage space, potentially greater fuel consumption, and often higher purchase and maintenance costs. Folks are also encouraged to give attention to “effective cutting width”, which is the actual width of the mown area for each pass. This can be significantly less than the stated deck (reel) width, so be sure to do your homework.

One of the most common and celebrated advancements to overcome maneuverability issues with larger rotary mowers is “zero-turn” capability. Zero-turn mowers are all about efficiency and were originally designed for lawn care operators and facility managers looking to cover more ground in less time. A great deal of the efficiency comes from the maneuverability… i.e turning on a dime compared to more traditional machines that require larger, slower, sweeping turns. This efficiency comes with a penalty, however, as the pivoting action of a zero-turn can create substantially more “collateral damage” in the way of plant injury and soil compaction, especially if mowing patterns are not varied regularly. Another means to mitigate these effects is to perform turns off of the turf surface (on a driveway, for example) whenever possible.

Then, ground speed. Mowers do indeed have optimum ground speeds for mowing that differ from brand to brand and machine to machine. Be sure to consider these optimum ground speeds in relation to your specific needs, as mowing at speeds higher than the equipment can handle most usually results in poor cut quality. Zero-turn mowers in particular are often also designed to mow at a higher ground speed relative to other mowing equipment - this is based on higher blade speed and other engineering factors - but precisely how fast varies based on the specific technology and manufacturer.

Note also that mowers, especially larger zero-turn units, are complex machines that fall very squarely into two categories: commercial or “consumer” machines. Commercial versions tend to be more resilient, reliable, repairable, etc., but unfortunately these benefits come at a financial cost, which these days can begin to rival that of a car or truck. Nevertheless, this cost can be a prudent investment for operators looking to take on larger properties or effectively service more properties over the course of a day. For facility managers and homeowners alike, larger, more nimble machines can translate to less valuable time spent on mowing activities.

Jason Lanier, UMass Extension Turf Specialist & Group Leader, Commercial Horticulture

Garden Clippings: Tips of the Month

April is the month to . . . .

• Start seeds of tomatoes, peppers, and eggplant indoors early in the month. Tomato seedlings transplant best when they are 6 to 8 weeks old, and lightly brushing the seedlings as they are growing indoors can help reduce height and yield more robust transplants. Start seeds of squash, cucumbers, and melons towards the end of April, in individual biodegradable pots. Growing seedlings in pots that can be transplanted directly into garden soil is gentler on plants that are sensitive to root disturbance.
• Water and fertilize houseplants more often, and check plants growing near windows to ensure they are not getting sunburned. Most tropical houseplants prefer low light conditions. As spring sunlight becomes more intense, move sensitive plants away from windows.
• Sharpen mower blades. Dull blades tear grass instead of cutting it. The tips of torn grass turn brown leaving the lawn looking ragged and poorly cut grass can be more susceptible to disease. Bare patches in the lawn can be repaired now: loosen soil with a garden rake before seeding, sprinkle with water, and cover lightly with straw.
• Prune summer- and fall-flowering shrubs before flower buds develop; avoid pruning spring blooming plants which have already developed flower buds. Remove winter mulch from the base of rose bushes and prune roses as the buds begin to swell but before new growth emerges.
• Protect transplants of cabbage, broccoli, onions, and lettuce in the garden from the drying effects of wind with a floating row cover made from lightweight, permeable fabric. Strong winds markedly slow the establishment rate and growth of transplants. Though some wind moves through the row cover, it is not enough to damage plants.
• Get going on landscape bed tasks: edging, weeding, and mulching. Apply landscape mulches no deeper than 2 to 4 inches—mulch that is too deep can reduce water infiltration—and remember to avoid mounding mulch against the base of plants. This is also a good time to position support hoops around perennials (such as peonies) while the plants are small.
• Consider mature size when planting new trees and shrubs in the landscape. When working with bareroot plant materials, store them in cool, moist conditions until planting. Soak the roots in water for about an hour prior to planting. Plant trees and shrubs at the correct depth in a generously sized hole—planting too deep or in a too-small hole can result in girdling roots.
• Wear tick repellent and conduct daily tick checks of people and pets. To help prevent tick bites, learn about tick borne diseases and tick borne disease prevention.
• Look for garden pests such as lily leaf beetle, a ¼-inch long, black-legged, bright red insect feeding on leaves of true lily species, Fritillaria, and occasionally lily-of-the-valley, Solomon’s seal, hollyhock, and hosta. Check boxwoods for leaf miner larvae. Small bumps on the undersides of leaves indicate that larvae are inside; the tiny green or orangey-yellow worm-like larvae are visible when affected leaves are peeled apart. Watch for cool season spider mite activity on broadleaf evergreens (e.g. andromeda, azalea, Japanese holly) and conifers (e.g. spruce, arborvitae, juniper, hemlock, pine). Damage appears as stippling on leaves or needles, and magnification is required to see mite eggs.
• Apply horticultural oil to trees and shrubs with scale, mite, and/or aphid problems. Carefully follow label directions for application rates, timing, and plant sensitivity.
• Set up a rain gauge near the garden to monitor rainfall and determine watering needs. Gardens need one inch of rain per week through the growing season. At this point, after several months of below-normal precipitation in the state, a rain gauge should be considered a critical gardening tool.

Jennifer Kujawski, Horticulturist

Spring Is Here…and so are peepers and ticks

Spring is finally here and for those people who were largely cooped up for the winter it’s a chance to get outside and resume favorite outdoor activities like gardening, walking, golf…you name it. It also triggers phone calls to me, including from the media, with the question…"Larry, when is tick season going to start and, is it going to be a bad tick year?”

The simple answer is that tick season runs from January 1st to December 31st. Many people are under the belief that a hard freeze in the fall is the end of tick season. This is true only for mosquito season. Ticks make a chemical that is essentially antifreeze. If you look at the tick activity chart the risk of tick bites in the winter is lower than summer but it is there. This corresponds with Department of Public Health data on incidence of tick-borne diseases like Lyme, the most predominant, but there are others.

We have a few species of ticks to be aware of. The most important one across the state is the deer tick. Public enemy #1. They transmit the pathogens that cause Lyme and other diseases. Dog ticks are also very common but are a lower threat statistically speaking. They can cause diseases like Rocky Mountain Spotted Fever, but it is very uncommon in northern states. Lone star tick seems to be confined right now to the Cape and Islands, but it will spread across the rest of the state over time.

So, what to do to protect ourselves? I speak to a simple 3 phase plan…Protect yourself, protect your yard and protect your pets. At the top of the list for self-protection is to treat clothing and footwear with a repellent that contains the active ingredient permethrin, which is available at sporting goods stores and many garden centers. This combined with tick checks prove maximum protection. You can also use a skin repellent containing DEET. A 30% concentration is sufficient.

Yard protection provides an additional layer of protection by a perimeter spray in May and June. Consult with a professional applicator for options such as bifenthrin. Avoid services that spray all natural products like botanical oils as research has shown they are completely ineffective.

For pet protection consult your vet because recommendations may vary depending on the pet's age and overall health.

Visit Cape Cod Cooperative Extension’s playlist of videos that covers topics such as permethrin treated clothing, perimeter yard sprays and pet protection.

Larry Dapsis, Retired Cape Cod Cooperative Extension Entomologist

Additional Resources

• For detailed reports on growing conditions and pest activity – Check out the Landscape Message
• For professional turf managers - Check out our Turf Management Updates
• For commercial growers of greenhouse crops and flowers - Check out the New England Greenhouse Update website
• For pollinator interests - Sign up for our newsletter, check out the Pollinator Buzz and follow us on Instagram.
• For home gardeners and garden retailers - Check out our home lawn and garden resources
• TickTalk webinars - To view recordings of past webinars in this series, go to: https://ag.umass.edu/landscape/education-events/ticktalk-with-tickreport-webinars

Diagnostic Services

• Landscape and Turf Problem Diagnostics - The UMass Plant Diagnostic Lab is accepting plant disease, insect pest and invasive plant/weed samples. By mail is preferred, but clients who would like to hand-deliver samples may do so by leaving them in the bin marked "Diagnostic Lab Samples" near the back door of French Hall. The lab serves commercial landscape contractors, turf managers, arborists, nurseries and other green industry professionals. It provides woody plant and turf disease analysis, woody plant and turf insect identification, turfgrass identification, weed identification, and offers a report of pest management strategies that are research based, economically sound and environmentally appropriate for the situation. Accurate diagnosis for a turf or landscape problem can often eliminate or reduce the need for pesticide use. See our website for instructions on sample submission and for a sample submission form at http://ag.umass.edu/diagnostics.
• Soil and Plant Nutrient Testing - The lab is accepting orders for Routine Soil Analysis (including optional Organic Matter, Soluble Salts, and Nitrate testing), Particle Size Analysis, Pre-Sidedress Nitrate (PSNT), Total Sorbed Metals, Total Carbon, Total Nitrogen, and Soilless Media. The lab is also accepting samples for Plant Tissue analysis, including macro and micronutrients, total carbon, and total nitrogen. Testing services are available to all. The lab provides test results and recommendations that lead to the wise and economical use of soils and soil amendments. For updates and order forms, visit the UMass Soil and Plant Nutrient Testing Laboratory web site.
• Tick Testing - The UMass Center for Agriculture, Food, and the Environment provides a list of potential tick identification and testing options at: https://ag.umass.edu/resources/tick-testing-resources.