Photo: Flickr / klm185

By Dirk Coburn, M.C.H.

Here at Weston Nurseries we're often brought strange and interesting specimens and rare plant diseases to diagnose. For the first time in my 12 years here, we have seen two confirmed cases of cedar-quince rust on Amelanchiers. One case was on a customer's tree that we recently inspected, and the other case was diagnosed by photos brought in by a homeowner.  Again, this occurrence of a condition not seen in a long time.

Cedar-quince rust is a lot like cedar-apple rust, only much rarer and more pernicious.  It requires a “cedar” host, which in our area is usually a juniper.  The native junipers are said to be somewhat more susceptible than the Asian ones.  It also requires a “quince” host, which can be any of a number of plants in the rose family, including fruiting quince (Cydonia), flowering quince (chaenomeles), hawthorn (Crataegus), apple (Malus), Amelanchier, or mountain ash (Sorbus), and possibly others.  The spores generated on one host must germinate on the other host.

Chaenomeles speciosa 'Cameo'

Unlike cedar-apple rust, cedar-quince rust does not just affect the leaves of the “quince” host.  It gets into the wood and causes lesions on twigs or branches that swell into gall-like structures.  The swollen segment erupts into fruiting bodies with an orange tinge that present the spores for dissemination.  Then the fruiting bodies fade and the gall shrivels and darkens into something that looks a bit like black knot.  Because these galls disrupt the cambium, cedar-quince rust can cause dieback pretty quickly.

There is no chemical treatment that can cure cedar-quince rust on its own.

If caught early, there is some hope that the affected wood can be pruned out.  Pruning should be done several inches below the galls/lesions, and the removed material should be burned, trashed, or buried – NOT composted or shredded.  After each pruning cut, the pruning shears should be sterilized with either rubbing alcohol or a 20% solution of chlorine bleach.  The tree should then be sprayed well with a general-purpose antifungal product;  propaconizole (the active ingredient in Infuse from Bonide) is a good choice because it soaks into the tissues and lasts a bit longer.

If the case is advanced, even those measures may not save the tree.  When the lesions/galls are plentiful and/or well distributed around the plant and/or present in the trunk or in major branches, it is advisable to remove the plant and to replace it with something suitable to the site and not susceptible to the cedar-quince rust.

PJM Rhododendron, a Weston Nurseries Introduction.

By R. Wayne Mezitt

Rhododendrons are such a significant component in many of this region’s gardens, and you likely have some in your yard. Can you recall such a spectacular display as we experienced this spring?! And now that they’ve finished blooming, some tasks that are effective and easy to accomplish will help assure your enjoyment continues next year.

When you visit your local garden center this time of year, you’ll likely see staff removing and discarding the spent flowers from many of the flowering plants, particularly annuals, they offer for sale. Horticulturists call this process “deadheading”. Deadheading surely enhances the appearance of the plants, and more importantly, it prevents them from forming seeds; it enables each plant to devote its energy to increased growing and forming new flowers.

Spent blossoms & seedheads.

Large-leaf rhododendrons and mountain laurel (Kalmia) can similarly benefit from deadheading. And it’s a simple task: let your fingers grasp and twist-off the entire seed-head at the tip of each flowering branch, taking care to leave the new growth shoots undisturbed. Don’t be overly concerned if some of the new shoots, leaves or branch-tip get removed during this operation—the latent growth buds will be stimulated and soon fill-in. The idea is to redirect the plant’s energy from seed-production into new growth. And the rhododendron (or Kalmia) will more than make up for the occasional loss of shoots by increasing its overall growth.

Seedpods tend to become more difficult to remove as they mature. And each cultivar differs in how tenaciously they hold-on to their seed-heads. Just as their flowers fade is the ideal time to do this, but even weeks later is still beneficial. And simply let the spent flowers drop beneath the plant—they eventually decompose and blend invisibly to become part of the mulch. The Early Rhododendrons (small-leaf types like PJM and Olga Mezitt) do not need deadheading because they set few seeds and are able to grow perfectly well naturally.

A rhododendron after being deadheaded.

Growing up in a nursery family, deadheading was one of the annual chores I was expected to perform. And I must say, deadheading hundreds of rhododendrons and Kalmia each summer was one task I didn’t relish very much. But now that I’m a homeowner with a more limited number of plants to maintain, I get a real feeling of accomplishment seeing how much reward I get for investing a couple hours.

Deadheading-time is also a good opportunity to remove dead and damaged branches and prune to control the height/spread of each plant. If you are unsure about how to deadhead specific plants, or whether it’s worth the effort, check with the experts at your local garden center.

Wayne Mezitt is a 3^rd generation nurseryman and a Massachusetts Certified Horticulturist, now chairman of Weston Nurseries of Hopkinton and Chelmsford, MA, and owner of “Hort-Sense”, a horticultural advisory business; he currently serves as Trustee chairman for the Massachusetts Horticultural Society at Elm Bank in Wellesley MA.

Once the Stewartia in my front yard starts to bloom in late June, I know summer has truly begun. A Cary Award winning tree, it is a reliable performer in this region with superb features and few pests. Easy to establish in your garden, it needs little or no care, and provides decades of enjoyment. Few winter hardy trees can rival the Japanese Stewartia (Stewartia pseudocamellia) for appeal this time of year, and its unique multi-season features add significant value to your landscape all year round.

In May Stewartia’s crisp, lustrous foliage emerges with bronzed tones, turning dark green by summer, followed by colorful orange, red, purple and yellow fall colors. Every day over several weeks from late June well into July, ruffled 2” diameter camellia-like (hence its name) nodding white flowers open successively along the stems. Interestingly, although each golden-yellow-centered blossom is open only a single day on the tree, the spent flowers always land face-up as they drop to the ground, creating a unique “bloom” effect on the ground beneath.

During the dormant seasons, starting when its October foliage drops, Stewartia’s distinctive bark features take center stage for the next 6 months until new buds again emerge in spring. The trunk and larger branches exfoliate, exposing mottled plates of pale orange, green and gray, creating a striking effect. These colors contrast robustly with winter’s snow or when grown against a darker background. For an even more impressive effect, try allowing the lower branches grow and arch-up naturally rather than pruning into a single trunk.

Stewartia grows well in full sun and partial shade and appreciates humusy, evenly-moist soil. Upright growing when young, it broadens a bit as it grows, reaching 25-30 ft. at maturity. It is a perfect centerpiece for a formal or patio garden, equally at home in a naturalistic planting. Because of its narrow, upright habit, interesting branching and year-round charm, it is a spectacular choice for lining a walkway, framed on both sides, and planted 10-15 ft. apart.

This is an underutilized tree that deserves to be up front in the landscape where its exquisite beauty can be appreciated every day all year long.

R. Wayne Mezitt is a 3^rd generation nurseryman and a Massachusetts Certified Horticulturist, now chairman of Weston Nurseries of Hopkinton and Chelmsford, MA. He has served as president of the Massachusetts Nursery and Landscape Association, the New England Nursery Association, and the American Horticulture Industry Association (“AmericanHort”), based in Columbus, Ohio and Washington, DC. Recently he’s formed “Hort-Sense”, a horticultural advisory business that utilizes his knowledge and experience for client benefit.

By Dirk Coburn, M.C.H.

Summer is here.  We have started the classic New England pattern of active cold fronts coming through our region and encountering moist air that has heated up during the day.  These fronts often generate brief rains or thunderstorms.  While our water tables are in good shape from the winter and spring, these rainstorms pose a potential threat;  if we think we can rely on them to water our landscapes, we may be disappointed.  A New England summer rain front often produces fairly little water on the ground.  Rains are often light and may evaporate before they even reach the ground.  When the rains are heavier, they are still not long.  Heavy rain in a brief period typically produces a high percentage of runoff.  The water from such a rain might wet the top couple of inches of soil, but a lot of the water goes into storm drains.  Relatively little soaks deeply into the soil near the root zones of trees and shrubs.

What are the implications for our landscape plants?

NEW PLANTS:  We cannot rely on Mother Nature to water newly planted trees, shrubs, perennials, or lawns in the summer.  It is too easy to kid ourselves that these summer weather fronts will cover for our busy lives – easy, that is, until we are facing plants that are wilting and failing to establish.  New plants need an intentional and diligent watering regimen for a full year (except when the ground is frozen for the winter) after their planting – ESPECIALLY in the summer.  Weston Nurseries’ watering guidelines for new plantings can be found on our web site here:  https://www.westonnurseries.com/watering-guidelines/.  If you will be away for part of the summer, you have several tools at your disposal:  e.g. tree watering bags such as the Treegator®; mulches that reduce evaporation from the soil; soil humectants such as Hydretain® that make the water in your soil more available to your plants’ roots; and friends, relatives, or hired help who can keep up watering during your absence.

A word about irrigation systems!  An irrigation system can sustain your plants or it can kill them.  New plants need watering that is:

• Deep Enough – to soak into the soil to a depth somewhat below their roots.
• Frequent Enough – to keep the roots from going bone dry and dying back between waterings.
• Not Too Frequent – so the soil can “breathe” between waterings and roots can exchange oxygen and carbon dioxide as they need to do.

These principles may dictate different watering cycles for trees and shrubs, perennials, lawns, annuals, and for each planter or container.  We recommend that you discuss these principles of watering in detail with your irrigation system designer or maintainer.  If you believe that a plant may be ailing due to water or lack of water, we may be able to recommend adjustments to your watering regiman for that plant.

ESTABLISHED PLANTS:  Right now, the spring has left us with water tables in good shape.  Unless we see a month or more of high temperatures with no rain, our established plants should be in good shape.  There is one caveat, however.  During last summer’s severe drought, some of our established plants may have seen some dieback of fine root mass.  If the root mass of a tree or shrub is out of balance with its branches and foliage, the plant may show signs of stress even during our current nurturing weather.  In this case, it might be helpful to stimulate some new root growth.  The quickest way to do so is with a liquid root stimulant;  Weston Nurseries carries one by Bonide called Plant Starter Concentrate.

Rhododendron catawbiense 'Album'

By R. Wayne Mezitt, WN Chairman

It has been many years since we’ve seen such superb, extended bloom on so many plants, particularly this week’s rhododendrons! An unusual number of favorable factors this year have combined to facilitate such an extraordinary season. Last winter lacked the extended cold and desiccating winds we often experience around here; April’s six days with temperatures >70°F made a big contribution by “fooling” many early-flowering plants into believing the season was more advanced that it was; the persistently cooler temperatures between the high peaks helped, along with no frost since the first week in April. And of major significance is all the rainfall that has finally ended our drought.

Now that rhododendron-blooming season is upon us, our weather continues to enhance the floral displays. Our consistently cooler-than-normal temperatures and periodic rainfall all are contributing to extending the flowering times in all our gardens. Perhaps this weather is not so encouraging for those of us who enjoy warm outdoor evenings around the pool or patio; but the plants love it!

So take a few moments to revel in this unusually-opulent display of bloom adorning so many homes and landscapes this spring—magnificence like this doesn’t occur very often!

By Dirk Coburn, M.C.H.

May is a great time to create or renovate a lawn.  Our lawn grasses in New England are cool-weather growers.  They germinate well in the late spring, the late summer, or the early fall.  Weston Nurseries has a full offering of tools, seeds, mulches, and treatments that are helpful for lawn projects.

Let me take a moment to talk specificly about the use of sod in a lawn project.  The following points respond to questions that we are asked frequently about sod:

• Sod farms grow their sod in locations spread widely around a region. Sod from each of these locations may look somewhat different due to local differences in soil at the farms.  However the crops are the same seed mix, and over time they will grow to look alike as they establish in their new environment.
• Sod from a location with sandier soil drains faster and may need more frequent watering, especially for the first two to three weeks. Twice a day for 10 minutes would not be out of line during that period.
• After the initial establishment period, watering should be less frequent and a little deeper. A lawn watered twice a week for at least 20 minutes each time will grow deeper roots than a lawn watered every day for 5 minutes, and will be more drought-resilient.
• Sod works best if care is taken to ensure that the underlying soil has good organic content. This may mean spreading half an inch or so of high organic loam if the underlying soil has low to moderate organic matter, or two inches or so if the underlayment is subsoil with virtually no organic matter.
• Sod works best if the underlying soil has been lightly tamped to promote good anchoring and then lightly scratched with a rake to give new roots entry points.
• Sod works best with a fertilizer designed for seeding or sodding, such as Jonathan Green’s Green Up Lawn Fertilizer for Seeding and Sodding.

Our sod grower has started recently harvesting from a farm in Maine where the soil is a little lighter colored and a little sandier than the soil in their other locations.  There are some benefits to the new sod, including:

• The lighter soil in the new farm assists the grower in keeping the sod free from fungal issues.
• The less dense soil is more penetrable by roots, and so with diligent care and watering it offers the potential to put new roots into a well-prepared substrate somewhat quicker.

Whatever method you may use for creating or renovating your lawn, Weston Nurseries’ staff of trained horticulturists stand ready to assist you in planning and if necessary troubleshooting your project.