By Dirk Coburn, M.C.H.

At Weston Nurseries we carry from time to time two types of bamboo plants:  clumping bamboo, and running bamboo.  The clumping genus that is hardy to our service area and that we carry when our growers offer a quality stock is Fargesia, the fountain bamboo.  I want to discuss running bamboos.  The genus that we carry from time to time is Phyllostachys.  In the past we have carried Pleioblastus, Sasa, and Sasaella which are also running bamboo genuses.

Running bamboo spreads by sprouting from rhizomes that migrate laterally underground.  Since bamboo shoots can be difficult to control through mowing, and can run under a walkway or in some cases even a driveway, it is a good idea in most cases to surround the entire bed with a root barrier. A deep foundation or other existing impenetrable wall at least 30 inches deep can form part of the barrier for a bed.

Weston Nurseries carries a heavy-duty polymer barrier product that can be inserted vertically into a narrow trench dug around a bed to contain the roots of running bamboo.  The barrier is 30 inches wide (so 30 inches deep when installed) and can be purchased by the foot. 

Root barriers can effectively control other rhizomous running plants, including:

·     Athyrium felix-femina – lady fern

·     Convallaria majalis – lily-of-the-valley

·     Dennstaedtia punctilobula – hay-scented fern

·     Pachysandra terminalis

·     Wisteria – especially the Asian species W. floribunda and W. sinensis

·     Xanthorhiza – yellowroot

Root barrier is not effective to inhibit aggressive spreading through above-ground stems or “stolons” that root where they touch the ground, or through dispersal of seed.  Spreading by stolons or by gravity-driven seeds can be discouraged by surrounding a bed with some combination of hardscape, pavement, a crushed stone bed, and mowed lawn.  Spreading by seed can further be discouraged by use of a pre-emergent weed control to inhibit germination of seeds that are spread by wind or by wildlife.  All of these methods – root barriers, hardscape, pre-emergent controls – can reduce the need for laborious hand-pulling or digging of undesired shoots and seedlings or for application of herbicides in our gardens.

Some plants spread by both rhizomes and another method, and may require both a root barrier and another control.  For example, Convallaria majalis spreads most aggressively by rhizomes and secondarily by seed dispersal.  Gardeners who want to contain that plant may want to consider both a root barrier and applications of pre-emergent controls.

Photo: Flickr / Benny Mazur

By Dirk Coburn, M.C.H.

In much of eastern and central Massachusetts we have grown used to fighting in the spring against tree defoliation by winter moth caterpillar and gypsy moth caterpillar.  If a substantially defoliated tree needs leaves, it is likely to push out a new set of leaves.  The resource that it most needs in order to do this is water.  In most years, two or three very deep waterings at two-week intervals would be appropriate to consider for a defoliated tree.  Groundwater is fairly plentiful this year, so an extraordinary deep watering is probably not necessary this year unless you have a very fast-draining soil.

But the threat of defoliation by pests does not disappear with the summer equinox.  Fruit trees can have a particular challenge if they are defoliated by Japanese beetles in July, while they are growing and ripening their fruit.  If the tree has a heavy load of fruit it can be helpful anyway, and certainly in the case of significant defoliation, to remove some portion of the fruit now and to let the tree concentrate its resources on fewer fruit.  The tree may do some culling for you by letting some fruit drop.  If you do some intentional culling, remove the smallest ones and cull evenly from throughout the tree.  Reducing the fruit load by anywhere from 1/4 to 2/5 should significantly alter the stress on the tree of fruit production and improve the prospects of a significant harvest in the current year.

In September any tree defoliated during the growing season could benefit from a feeding with a fertilizer with a major nutrient profile of 8-8-8- or 10-10-10.

What should you do in future seasons if your fruit tree is defoliated by Japanese beetles?  Any tree that is substantially defoliated prematurely three years in a row is at high risk of mortality.  For this reason, you should be prepared the following year to treat your defoliated fruit tree at two-week intervals starting at the very end of June and continuing until Japanese beetles have disappeared from your landscape.  A spray based on Spinosad would be appropriate, such as Captain Jack's Dead Bug Brew by Bonide that we carry.  Treat the trees at dusk, just after sunset, when bees and other pollinators are typically not foraging.  The spray will dry on the leaves overnight.  Its toxicity to insects that do not feed upon the foliage will drop to near zero, but the treatment will remain effective with the Japanese beetles that feed on the foliage.  If we get a moderate to heavy rain while the beetles are out, re-treat the tree when the leaves are dry and reset the two-week clock for the next treatment.

An additional or alternative strategy involves planting lower fodder for the beetles.  The beetles pupate in the ground and usually start feeding from the ground up.  So planting perennials or low shrubs that they feed on can delay their rising to feed on your trees, potentially long enough to result in little or no damage to the trees before the beetles lay their eggs in the ground and die.  This strategy has the advantage of being pesticide-free, though not costless.  On the downside, this strategy does nothing to control the population of the beetles.

Photo: Flickr / F.D. Richards

By R. Wayne Mezitt

Starting in August and continuing well into autumn, it’s hard to miss the ubiquitous sprays of yellow on roadsides, meadows and other untended sunny sites. The profuse flower-heads of goldenrod vary in color intensity, size and shape; all are yellow-flowering, and depending upon species, their height and spread can be less than a foot tall and wide to more than six feet. Two dozen or more distinct species are native to this region, coming into bloom at differing times, extending the season of color to as much as three months.

Goldenrod (botanical name: Solidago) is a superb pollinator plant. Its protracted flowering season attracts many species of bees, butterflies and other pollinators, making it an ideal choice for native wildflower gardens and meadow plantings. Goldenrod honey is dark and spicy and it has become a popular consumer product with beekeepers. Goldenrod’s diverse flower-plumes also make wonderful, long-lasting cut flowers, particularly in combination with contrasting blooms of other wildflowers.

Until recently, goldenrods were seldom grown as garden plants in the USA. Probably because they are so ingenuous in nature, gardeners in this region consider them to be a “weed”. And that’s not entirely unwarranted: some types can rapidly develop into a problematic garden “thug” due to their propensity to germinate and grow quickly from wind-dispersed seed. Once settled-in for a year or two, removing a heavy clump with its dense mat of roots and rhizomes can be a hefty challenge; and even only a small piece left behind will regrow into a robust plant next season.

But in European gardens, goldenrod has long been favored as an attractive summer-flowering perennial, a major garden feature. Thanks to hybridizing successes, the cultivars and hybrids now coming onto the market are much better suited to our gardens with far better performance attributes and less propensity to spread and dominate. Look for names like ‘Fireworks’, ‘Golden Fleece’, ‘Solar Cascade’ and ‘Golden Baby’ at your local garden center. There’s even a variegated-leaf cultivar of zig-zag goldenrod, Solidago flexicaulis ‘Variegata’, adding its yellow-splashed foliage appeal before the blooms appear.

By now you probably know that goldenrod has been wrongly accused of causing hay-fever. That’s because it blooms concurrently and in the same areas with the less conspicuous ragweed, whose pollen is readily carried on the wind. Goldenrod pollen grains are heavy, requiring physical assistance from bees and butterflies to be transported. So spend a few minutes noticing all the goldenrods this season—you may be pleasantly surprised when you take the time to appreciate such a bounty of color and form!

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.

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!