Hort Notes 2020 Vol. 31:2

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

To read individual sections of the message, click on the section headings below to expand the content:

COVID-19 Information for Landscapers, Garden Centers, and Nurseries

During these challenging times, everyone is taking extraordinary measures to help protect the health of ourselves, our families, our employees and our communities. In Massachusetts, Governor Charlie Baker has issued an emergency order requiring all businesses and organizations that do not provide “COVID-19 Essential Services” to close their physical workplaces and facilities to workers, customers, and the public as of Tuesday, March 24th at noon until Monday, May 4th (however, this end date may change so it is important to follow updates at mass.gov). These businesses are encouraged to continue operations remotely.

NOTE: These guidelines are likely to change as the COVID-19 situation in Massachusetts continues to evolve. These updates are as of April 4, 2020.

Landscaping and Tree Removal Operations

The information below is taken from the updated FAQ from the Commonwealth's official COVID-19 site at https://www.mass.gov/info-details/covid-19-essential-services-faqs (scroll down to the Construction-Related Activities heading). Continue to check this web site for further updates, as this information is rapidly changing. Landscaping is considered essential if the services being provided are necessary to maintaining the safety, sanitation, and essential operation of residences, businesses, and other buildings. Non-emergency tree removal is designated as a non-essential service; however, these companies may continue operating remotely if they maintain compliance with the social distancing guidelines from the official MA COVID-19 mandate and directives from the MA Department of Public Health.

Q. Can businesses that don't operate out of a bricks-and-mortar location continue to operate?
A. YES with social distancing. If the service a business provides is not on the essential services list, that business must cease all in-person activities at its bricks-and-mortar facilities. These non-essential businesses are encouraged to work remotely. Businesses that do work remotely, whether as part of their normal activities or as a result of this order, must maintain social distancing requirements: six feet of separation between all employees, and between employees and members of the public.

Q. Is landscaping an essential service?
A. YES if providing services that are necessary to maintaining the safety, sanitation, and essential operation of residences, businesses and certain other buildings (see list at https://www.mass.gov/info-details/covid-19-essential-services for full details).

Q. Is non-emergency tree removal considered an essential service?
A. NO but you may be able to continue operating. If the service a business provides is not on the essential services list, that business must cease all in-person activities at its bricks-and-mortar facilities. These non-essential businesses are encouraged to work remotely.  Businesses that do work remotely, whether as part of their normal activities or as a result of this order, must maintain social distancing requirements: six feet of separation between all employees, and between employees and members of the public.

Nurseries, Greenhouses, and Garden Centers

Q. Are nurseries essential?

A.Yes, if they sell food or food plants and follow DPH guidance.

Nurseries, greenhouses, garden centers, and agriculture supply stores that sell food or food producing plants for human consumption have been designated as COVID-19 Essential Services and may therefore continue to operate their brick and mortar premises. Workers supporting these operations are included within the COVID-19 Essential Workforce for approved purposes. These operations that remain open for business must deploy strategies to reduce COVID-19 exposure for their customers and employees by following DPH guidance. These guidelines are detailed at https://www.mass.gov/doc/dph-nurseries-guidance/download. Any nursery, greenhouse, garden center or agriculture supply store that sells solely plants that do not produce food for human consumption shall remain closed. 

For more information about protecting yourself and others from coronavirus, please visit: 
https://www.mass.gov/resource/information-on-the-outbreak-of-coronavirus-disease-2019-covid-19  

Does Your Pesticide License Recertification Cycle End 7/1/20?

For holders of Massachusetts pesticide licenses whose current three-year retraining or recertification cycle ends in Calendar Year (CY) 2020, the MA Department of Agricultural Resources Pesticide Program has extended the time permitted to earn credits to 12/31/20 as well as the number of computer-based or online credits that are acceptable for these specific individuals. For more details, go to https://www.mass.gov/doc/pesticide-license-recertification-processes-and-related-impacts-from-covid-19/download

Featured Plant

Spring Bulbs

As temperatures warm in March and April, the search for signs of plant growth begins. Some of the most exciting finds are the first leaves of the early spring bulbs. The emergence of crocus, snowdrops, and early daffodils and tulips provides a moment of hope for gardeners that spring has arrived. Although bulbs are generally associated with the Netherlands, from where many are exported, bulbs are native to a variety of places around the world.

Almost synonymous with the Netherlands, the tulip (Tulipa) is native to an area around the Pamir Alai and Tien-Shan Mountain Ranges near the Russian-Chinese border. They first gained popularity in Turkey during the Ottoman Empire and were brought to the Netherlands in the 1500s. There are approximately 150 different species of tulips, and they are organized into 15 divisions based on flower shape, origin, and bloom time. Along with the traditional cup-shaped flowers, there are doubles, contrasting eyes and penciling, lily-like flowers, fringed tepals, streaked flowers, and contrasting bases. The Rembrandt group, long one of the most desired varieties, is no longer sold in commerce because the desired striping is caused by the tulip breaking virus (TBV). These were some of the most highly sought-after bulbs during "Tulipmania" in the Netherlands in the 1500s and included the Semper Augustus. Animal pests are generally the largest problem for the bulbs, with squirrels frequently digging up newly planted bulbs. Tulips are planted in the fall at a depth of 3 times the height of the bulb. After flowering, spent flowers can be removed but foliage should remain until the leaves yellow. Although tulips are perennials, they are commonly treated as annuals because performance declines after the first year. 

Daffodils (Narcissus) are native to Spain and Portugal. Also referred to as jonquils in some areas, jonquils are actually one species which have multiple small flowers on each stem. Daffodil flowers are generally a trumpet or cup surrounding by six petals. Colors include yellow, white, orange, pink and bicolors. Other flower variations include the size or length of the trumpet/cup, double flowers, number of flowers per stem, reflexed petals, fragrance, time of bloom, length of stem, and miniatures. Daffodils are best grown in a slightly acid, well-drained soil in full sun to part shade. Similar to tulips, daffodil bulbs should be planted in the fall at a depth of 2 to 3 times the height of the bulb. Also similar to tulips, the flower stem can be removed after flowering but leaves should remain until they yellow to allow replenishment of food reserves in the bulb. 

Snowdrops (Galanthus) are native to Europe and the Middle East. Flowers consist of six tepals in two whorls, with outer tepals being spreading and inner whorls being shorter. These flowers are some of the first to emerge in spring, often when there is still snow on the ground. Galanthus nivalis, or common snowdrop, has naturalized in parts of eastern North America. Galanthus elwesii, or giant snowdrop, has larger flowers, leaves, and overall size than the common snowdrop. Cultivars offer features such as green marking on tepals, double flowers, the angle of the tepals (dropping vs. spreading), and the length of the stems. Snowdrops do best in a well-drained soil in full sun to part shade. Ideal conditions would provide full sun in early spring becoming part shade as trees or shrubs leaf out. These bulbs are deer and rodent resistant. Bulbs should be planted 2-3” deep and care should be taken to wear gloves as skin irritation can occur.

There are over 90 species of Crocus, which are native to North Africa, the Middle East, central and southern Europe, and Western China. Crocus “bulbs” are actually corms. The commonly planted crocus includes species or botanical crocus and the Dutch large flowering crocus. The “species” group includes a number of species that grow to around 4” tall, have six petaled flowers, and grass-like foliage. Flower colors range from white to yellow to purples to orange with bicolored petals and striping. The Dutch large flowering crocus bloom about two weeks after the species crocus and grow to 5” tall. Flowers are similar to the species but larger. Crocus are best sited in full sun to part shade in a well-drained soil. Rodents are particularly fond of crocus corms. Plants will naturalize over time and should be divided every 4-5 years. No matter the selection, the emergence of early spring bulbs helps to signal the arrive of spring and warmer days to come. 

Mandy Bayer, Extension Assistant Professor of Sustainable Landscape Horticulture

Questions & Answers

Q. What can I do to improve the health of my flowering cherry?

A. Flowering cherries are one of the most common and neglected trees in our managed landscapes. Available almost everywhere for purchase, ornamental cherry stock can be less than ideal. For much of the year, flowering cherries provide only limited garden interest but all their shortcomings are forgotten when in full bloom. Admiring the cascading pink to white blooms of a mature flowering cherry, contrasted against the dark brown branches and trunk, is one of the annual rites of spring. 

First, it’s important to recognize that many ornamental cherries, such as Prunus serrulata and P. subhirtella, are generally short-lived trees that will not persist indefinitely in the managed landscape. Ornamental cherries are especially susceptible to deep planting and the development of girdling roots, which may shorten the life of these trees even further. Air spading or careful removal of soils around the base can help to understand the scope of the problem and may extend the life of the tree if the root flare is exposed and girdling roots can be safely pruned. Bark cracking and splitting on the main trunk from sun scald and freezing is also a common abiotic stress. These large longitudinal splits and cracks can facilitate insect colonization and kill sapwood and cambium tissues. Sun scald and freeze wounds often develop on south and southwesterly facing sections of the trunk, so avoiding fully exposed settings when choosing a planting site can be beneficial. 

With regards to diseases of the canopy, regular sanitation pruning of dead shoots and branches should be performed on an annual to biennial basis to reduce the presence of cankering pathogens and improve aesthetics. Opportunistic pathogens like Phomopsis, Botryosphaeria and Cytospora can be problematic for these trees if not treated, especially on dwarf, weeping cherries with dense, compact canopies. Brown rot of stone fruits, caused by Monilinia fructicola and M. laxa, causes shoot and leaf blight, fruit rot and canopy dieback. Shoot and stem cankering, along with other dieback symptoms, can also be caused by the bacterial pathogen Pseudomonas syringae. Regular scouting and immediate pruning of flagging shoots and branches can limit their spread in the spring. In late winter, scout for “mummified” fruit in both the canopy and around the base of the tree, if the tree produces fruit. Remove or cover these infected fruits as they provide a large source of inoculum to create new infections. Pruning to improve sunlight penetration and air flow in the canopy can also be beneficial in controlling cankering pathogens. 

Blumeriella leaf spot, caused by Blumeriella jaapii, is perhaps the most widespread foliar disease of cherries. Infections result in reddish-brown leaf spots that develop early to mid-summer and when numerous, cause premature leaf yellowing and shedding. In some cases, the leaf spots are isolated and the dead tissue falls away, creating a shot hole appearance. For trees with chronic infections, preventative fungicide applications, performed early in the growing season when new leaves are expanding, may help to limit the initial colonization of fungal spores. However, bacterial leaf spot, caused by Xanthomonas and Pseudomonas, can also produce the shot hole symptom so field identification alone may not be sufficient for pathogen identification. For this reason, fungicides that also act as bactericides (e.g. copper-based products) may be the best option for treating foliar diseases on ornamental cherries. 

Finally, larger neighboring trees may be completely shading out a flowering cherry that once ago received sufficient sunlight. A lack of sun may be the primary cause of decline and before any intervention takes place, it’s prudent to ask whether the tree has outlived its purpose in that particular setting. Removal of any tree or shrub in the garden is unfortunate but creates an opportunity to plant something else in its place.  

 

 

 

 

 

Nick Brazee, UMass Extenstion Plant Pathologist

Trouble Maker of the Month

Are There Glyphosate Alternatives? 

Garden Clippings Tips of the Month

April is the time to:

• April is a good month to rake the lawn.  Rake the turf lightly with a leaf rake, do not use a garden rake as it will damage the turf, and avoid any raking if conditions are too wet. Raking will remove dead and blighted blades and other debris, facilitate recovery from snow mold (if any), and help to promote good regrowth.

• If areas of the lawn were damaged during the winter, April is a good time to repair those areas. A starter fertilizer that contains nitrogen (N) and phosphorus (P) is beneficial for the establishment of young turf seedlings and is permitted by Massachusetts plant nutrient regulations. Keep the seeded area moist throughout establishment by watering lightly multiple times a day to avoid runoff and washing. A covering of mulch will help to keep repaired areas moist and reduce watering frequency. Avoid applying herbicides to repaired areas during the spring as this may cause injury to new plants.

• Cut back any ornamental grasses and perennials you left in place for winter interest or bird feeding. Cutting ornamental grasses back before new growth emerges will make the clumps sturdier. If you wait too long to cut back the old stems and leaves, you’ll likely snip off the tips of new leaves.

• Divide perennials. Many perennials tend to die out from the center if not divided on a regular basis. The frequency of dividing perennials depends on the species. Most perennials respond best when divided in early spring. In early spring the weather is cool and there is usually adequate moisture in the soil. Roots have a lot of stored energy that will help the divisions recover from being cut apart and replanted. The new emerging shoots are likely to suffer less damage than fully developed growth and will also lose less water through evapotranspiration. Spring divisions also have the entire season to recover from the stress of division. Start by digging around the plant, then lift the entire clump out of the ground. Using a spade or sharp knife, cut the clump up into separate pieces. Discard the old, dead center and trim off any damaged roots. Keep the divisions moist and shaded while you prepare the new planting site. After replanting. keep them well watered.

• Prune summer and fall flowering shrubs. Early April is good a good time to prune summer flowering shrubs such panicle hydrangea, butterfly bush, buttonbush, summersweet clethra, sweetspire, and summer flowering spirea, since these shrubs form their flower buds on the current season’s stem growth. Pruning these in winter or early spring leads to vigorous stem growth in spring and summer that contain the buds that will flower in summer and early fall.

• Prepare garden soil for spring planting. Do not work your soil when it is wet. Tilling or digging when the soil is wet will cause it to dry into hard clods. Prepare soil when it has dried enough. To test if your soil is dry enough, take a handful of soil and squeeze it. If the soil crumbles easily when you open your hand, it is ready to be tilled. If it does not crumble, it is too wet. Allow the soil to dry for a few more days and test again before digging. Prepare raised beds in areas where cold soils and poor drainage are a continuing problem. Incorporate generous amounts of organic materials.

• Sow seeds of cool season crops in the field. Seeds of leafy greens such as lettuce, chard, kale, or arugula and roots crops such as carrot, radish, beet and turnips can be planted in the field in April. Plant the seeds as soon as the ground can be worked. You can also set out transplants. Transplants are preferred for leafy vegetables such as kale and chard as they establish faster and mature early. Cool season crops such as spinach, beets, radish, carrots and lettuce are sowed thickly in rows and thinned later to the desired stand and to allow them to develop properly. Root crops such as carrots, beets, and radishes should be thinned to a 2-inch spacing to allow the roots to develop properly. They can be thinned as soon as they reach small edible size. 

• Start seeds of warm season plants indoors. Seeds of warm season plants such as tomatoes, cucumbers, eggplants and peppers can be started indoors in April for transplanting later to the garden when it gets warmer. Starting your vegetable seeds early will give your garden a jumpstart on spring by having plants ready when you want to transplant. When selecting vegetable varieties, check for the number of days needed to harvest. Make sure you follow seed packet or catalog instructions, as each species has its own requirements. Make sure you have indirect but high light around all plants. The more light the better, up to 16 hours a day. Use cool white spectrum fluorescent fixtures or grow lights suspended 6-12 inches above the plants and make sure you move the lights up as plants grow. If you don’t have grow-lights, place your plants on a south facing window, but make sure to rotate the containers to get sturdy, uniform straight plants. Providing bottom heat speeds up germination and produces healthier roots and plants, and can prevent “damping off” disease that causes death of tiny seedlings. Electric heating mats specifically for seed starting are available from many garden centers.

• Plant cold tolerant flowers. Pansies and other cold tolerant flowers such as petunias and snapdragons can be planted in April. Place these plants where they will receive full sun. Some pansies may tolerate partial shade. Water plants thoroughly after planting and mulch lightly with organic mulch if possible.

• Plant balled and burlapped (B & B) trees and shrubs. Balled and burlapped (B & B) trees and shrubs (especially species known to be slow to establish new roots) do best if planted in the early spring before or just as new growth starts.

• To celebrate Arbor Day on April 24, plant a tree. Arbor Day is an annual observance that celebrates the role of trees in our lives and promotes tree planting and care.

Geoffrey Njue, UMass Extension Sustainable Landscapes Specialist

The Perks and Price of Planting Street Trees

Officially declared by Congress as America’s National Tree in 2004, the oak boasts a long history of cultural significance. This stately tee has served as a landmark throughout the centuries and is recognized to this day for its size, stature, abundance, and diversity. With nearly 60 different species native to the United States alone, oaks are the most widespread hardwoods in North America. It makes sense then, given their common presence in our rural forests, that many species of oak are popular street trees. In addition to the lumber products and wildlife benefits they provide, oaks are hardy shade trees that, in some instances, may offer brilliant fall color.

Upcoming Events

Operations at the University of Massachusetts Amherst have been significantly reduced in response to the COVID-19 pandemic. All in-person UMass Extension events scheduled through May 4 have been canceled or postponed, including pesticide exam preparation and recertification courses, MassAggie workshops, and the Spring Kickoff for Landscapers. All professional staff are working remotely and are unable to travel for work at this time. We are doing our best to maintain and expand our remote educational services and to continue to participate remotely in meetings and events where possible.

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Other Upcoming Events:​

Tune in to a TickTalk with TickReport webinar, a FREE live webinar series by Dr. Stephen Rich, Director of the UMass Laboratory of Medical Zoology. Noon to 1:00 pm on the 2nd Wednesday of the month. Co-sponsored by UMass Extension and the UMass Laboratory of Medical Zoology.

• 4/8 - Update from TickReport: includes the status of the lab during the COVID-19 response, summary data of the current Spring tick season in Massachusetts and beyond, and based on prior year's data, forecasts of what we may expect for tick activity in the coming weeks. Register at https://ag.umass.edu/landscape/education-events/webinars
• May-Dec: noon to 1:00 pm on the 2nd Wednesday of the month

New Online Offerings: 

• Check Out InsectXaminer! This new short video series hopes to increase the visibility of the beautiful world of insects, even those we consider to be pests in our managed landscapes. One thing you don't have to worry about this spring? Gypsy moth! Thanks to the gypsy moth caterpillar killing fungus, Entomophaga maimaiga, the recent outbreak of this invasive insect has come to an end! Most locations in Massachusetts will not see damaging or even noticeable populations of this insect in 2020. Missing gypsy moth already? Check out Episode 1 of InsectXaminer to reminisce about the 2015-2018 outbreak of this insect, available here: https://ag.umass.edu/landscape/education-events/insectxaminer 

Registration for the following events has been temporarily suspended while we await further guidance regarding public gatherings from public health officials and the University of Massachusetts. 

• 5/19 - Weed Walkabout
• 6/4 - Landscape Pests & Problems Walkabout: Diseases & Weeds
• 6/11 - Ornamental Tree & Shrub ID and Insect Walk
• 6/25 - Landscape & Forest Tree & Shrub Insect Workshop
• 7/8 - State Regulations Pertaining to Invasive Plant Management (part A2: Invasive Plant Management Certification Program)
• 8/5 - The Invasive Plant Issue and Invasive Plant Identification (part A3: Invasive Plant Management Certification Program)
• 8/19 - Developing an Invasive Plant Management Program (part B: Invasive Plant Management Certification Program)
• 9/9 -  Ornamental Tree & Shrub ID and Insect Walk
• 10/26-12/10 - Green School

For more details for any of these events, go to the UMass Extension Landscape, Nursery, and Urban Forestry Program Upcoming Events Page. 

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Additional Resources

For detailed reports on growing conditions and pest activity – Check out the Landscape Message

For commercial growers of greenhouse crops and flowers - Check out the New England Greenhouse Update website

For professional turf managers - Check out our Turf Management Updates

For home gardeners and garden retailers - Check out our home lawn and garden resources. UMass Extension also has a Twitter feed that provides timely, daily gardening tips, sunrise and sunset times to home gardeners at twitter.com/UMassGardenClip

Diagnostic Services

Current Massachusetts and University policy have the effect of temporarily suspending most of the on-campus services that we provide, including but not limited to:

• Soil and Plant Nutrient Testing Lab
• Plant Disease Diagnostics Lab
• Weed, Insect, Turfgrass, and Invasive Plant Identification

These services are currently suspended. Until further notice, please do not send or deliver samples to the campus, as we cannot process them.

A UMass Laboratory Diagnoses Landscape and Turf Problems - When normal services resume, the UMass Extension Plant Diagnostic Lab is available to serve 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. For sampling procedures, detailed submission instructions and a list of fees, go to Plant Diagnostics Laboratory. No samples are being accepted at this time.

Soil and Plant Nutrient Testing - When normal services resume, the University of Massachusetts Soil and Plant Nutrient Testing Laboratory is located on the campus of The University of Massachusetts at Amherst. Testing services are available to all. The function of the Soil and Plant Nutrient Testing Laboratory is to provide test results and recommendations that lead to the wise and economical use of soils and soil amendments. For complete information, visit the UMass Soil and Plant Nutrient Testing Laboratory web site. Alternatively, call the lab at (413) 545-2311. No samples are being accepted at this time.