How To Cope With Boxwood Blight: An Expert Weighs In

It’s not every day you get to discuss your problems with an international expert. But Lynn Batdorf is the real deal. Batdorf is the world’s top resource on everything boxwood, including all of the diseases and pests that affect this diverse species. Recently he spoke to me about how to deal with the latest threat to our gardens, the dreaded boxwood blight.

WHERE DID BLIGHT COME FROM, ANYWAY?

Given its rapid spread, you could be forgiven for assuming that boxwood blight is a recent arrival. But in fact, the fungus was first reported in the United Kingdom in the mid 1990s. Following its discovery, the disease quickly spread across Europe and New Zealand before landing in North America in 2011. In the years since, it has been decimating landscapes across the world at alarming rates.

Boxwood blight was first discovered in the United Kingdom in the mid 1990s.

SIGNS AND SYMPTOMS OF BLIGHT

Boxwood blight is caused by the pathogen Calonectria pseudonaviculata which causes leaf spots, stem cankers, defoliation and eventual death of the shrub. The fungus usually begins on the bottom branches and moves up the plant by splashing water. It begins as dark leaf spots with a black ring, which Batdorf refers to as ‘frogs’ eyes.’

Boxwood blight leaf spots

Soon after the spots appear, they expand to cover the entire leaf and the blighted leaves begin dropping from the plant. The disease next progresses to the stems, forming narrow black streaks called cankers. As the cankers enlarge, they girdle the stems and the twig dies.

Photo: Landis Lacey & Kelly Ivors, NCSU Dept. of Plant Pathology

Blight infects all the above-ground parts of the plant and will cause defoliation of the entire shrub in less than 10 days. As Batdorf puts it, the plant simply dies from exhaustion. Indeed, each time the boxwood tries to recover and produce a new leaf, blight spores hop back up on it. Eventually the shrub succumbs, deprived of its source of life-giving energy.

Row of infected boxwood in Connecticut/Photo: Sharon Douglas, Ph.D., CAES

TRANSMISSION

Although it can at first resemble other boxwood diseases such as Volutella and Macrophoma, the main thing that sets blight apart are its spores. Said to live up to 5 years in the soil, they are nearly impossible to eradicate. As a result, once boxwood blight has appeared on a plant, it will most likely keep reappearing.

To make matters worse, during growing season transmission of the disease is usually splash-related. This means it generally occurs through irrigation or rainfall, both of which easily spread blight to nearby shrubs.

Irrigation helps spread the disease.

Moreover, boxwood blight can overwinter on infected plants or hide in leaf litter. It is also transmitted by tools, lawn mowers, leaf blowers, vehicles that contain infected leaves and pets. And host plants include all members of the boxwood family such as pachysandra and sarcococca. Recently, these two popular ground covers have also shown signs of being infected by the fungal disease.

A new host, pachysandra can also spread blight/Photo: CAES

STRATEGIES FOR COPING WITH BLIGHT

So what’s a gardener to do? Up until now, there have been few options. More recently, instituting a preventative fungicide spray program has shown some promise in protecting non-infected plants. However, since the spores live for so long in the soil, this involves expensive, bi-weekly spraying during the growing season for at least five years.

For those who aren’t comfortable or able to invest in such measures, Batdorf (who is not a fan) offers some suggestions. He recommends first that you only purchase from reputable nurseries. Sadly, he says you should no longer buy English box. It is the most susceptible of all.

English box is the most susceptible of all varieties.

Second, he advises against shearing plants when wet. Boxwood blight thrives in humidity and moisture.

Avoid pruning in wet conditions.

Third, Batdorf recommends you collect and remove all leaf debris that may be harboring spores. And, don’t compost dead leaves in the vicinity of boxwood plants. 

Don’t compost near boxwood plants.

If you do diagnose blight on your boxwood, remove and destroy the plants. Then dig out the infected soil and replace with clean soil. Replant with a different species. Unfortunately, other boxwood, even so-called resistant varieties, are no longer candidates for that space.

OTHER NON-HERBICIDAL STRATEGIES

Whether or not you’ve decided to use fungicides, here are Batdorf’s three main recommendations for helping to prevent boxwood blight on healthy shrubs. (The key thing to remember is that blight loves to spread by splash from soil to plant.)

Remember, boxwood blight spreads primarily by splash.

1. APPLY 1″ OF PINE BARK MULCH

Apply 1″ of mulch (not 2″ or 3″, which can hold too much moisture) around the plant’s drip line to prevent splash. Batdorf recommends pine bark over hardwood for its better aeration. Hardwood can suffocate boxwood’s delicate surface roots.

2. LIMB UP THE BRANCHES

Limbing up the branches by 6 to 8 inches will help prevent splash up from the soil.

3. PRACTICE SANITATION

Regularly vacuum up the area under your boxwood to remove all dead leaf debris, which is a major cause of infestation.

Clean up all dead boxwood debris.

BEST DISEASE-RESISTANT BOXWOOD CULTIVARS

Finally, although there are no known resistant boxwood, some have been found to be more tolerant than others. One of the best ways to limit your exposure is to plant less susceptible varieties. Below are some recommendations.

DO NOT PLANT. At the top of the list are ENGLISH BOX, Buxus sempervirens Suffruticosa and Buxus sinica var. insularis Justin Brouwers. Other highly susceptible cultivars include Buxus sempervirens Marginata and Buxus sempervirens Elegantissima.

Buxus sempervirens Elegantissima

BETTER choices are Buxus microphylla Jim Stauffer, Buxus X Green Mound and Green Mountain.

BETTER STILL are Buxus microphylla japonica Winter Gem, Buxus sempervirens Dee Runk, Buxus hybrid Green Gem and Buxus microphylla John Baldwin.

BEST OF ALL and recommended for all new plantings are Buxus sinica var. insularis Nana and Buxus microphylla japonica Green Beauty.

For more information on Lynn Batdorf, the U.S. Arboretum’s National Boxwood Collection (which he curated for 36 years) and his many books, articles and lectures, click here for his website. He also provides on-site consultations.

 

Why Star Magnolia Deserves A Spot In Your Garden

Magnolia stellata, commonly known as Star Magnolia

First introduced from Japan in the 1860s, star magnolia has long been a resident of the American garden. One of the smallest magnolias, it produces a cloud of showy white or pink flowers in early spring. The blossoms appear before the leaves, dangling like fallen stars on the tree’s smooth, bare branches. It’s enough to leave you speechless. Continue reading

The Best Hellebore Varieties For Your Winter/Spring Garden

February can be a bleak time on the East Coast. Days are short and the sky hangs low on the horizon. But there’s a small-sized perennial whose early, colorful blooms never fail to lift my mood. It’s the lovely, cup-shaped flower called hellebore, commonly known as the Lenten Rose. Continue reading

Clear the Air With These 10 No-Fuss Houseplants

Peace lilies can help clear the air of harmful toxins

According to the Environmental Protection Agency (EPA), Americans on average spend 90 percent of their time indoors. And indoor environments can be poor, trapping dangerous chemical toxins as well as bacteria, pollens and mold. Continue reading

Managing Hydrangeas: To Prune Or Not To Prune And Other Existential Questions

To prune or not to prune? That is one of the quintessential gardening questions. Continue reading

How To Say What You Mean In The Language Of Flowers

Different flowers and flower colors carry different shades of meaning

Studies show that mastering a foreign language can not only boost your brain power but also provide you with insight on how the world thinks. Unfortunately, not everyone can learn with the same facility. But there’s one second language we all know how to speak fluently, albeit with slight variations. Colorful and often emotional, it’s called the Language of Flowers.

THE VICTORIAN LANGUAGE OF FLOWERS

Back in Victorian times, people knew how to ‘say it with flowers.’ The 1800s were a buttoned-up era, with many taboos against expressing emotions. To get around the rules, people borrowed from an ancient language to convey their feelings. They used flowers and floral arrangements as coded messages.

Mother’s Day card circa 1890

Sometimes referred to as floriography, the Language of Flowers can be traced back to ancient times. This includes the Hebrew Bible, where plants and flowers often figure as symbols. The Song of Songs is one such example:

I am the rose of Sharon, and the lily of the valleys. 2.As the lily among thorns, so is my love among the daughters. 3 As the apple tree among the trees of the wood, so is my beloved among the sons. I sat down under his shadow with great delight, and his fruit was sweet to my taste. Song of Songs 2:1-3

Apple tree blossoms

THE TULIP’S TURKISH ROOTS

However, the practice of floriography most likely had its roots in Turkey, where in the 16th century, the Court in Constantinople was said to have an obsession with tulips. Following their discovery in the mountains, many powerful people started cultivating the cup-shaped flowers in their gardens. 

Tulips were an obsession in the Court of Constantinople

Eventually, as Ottoman sultans began wearing tulips in their turbans, they became symbolic of wealth and power. Not surprisingly, the flower’s name is believed to derive from the Persian word tulipan, meaning turban, with which it shares an uncanny resemblance.

The word tulip comes from the Persian tulipan, meaning turban

TULIPS IN THE HAREM

In the Western World, we have Lady Mary Wortley Montagu to thank for introducing the language of flowers to Britain. In 1716, she accompanied her husband to Turkey where he was stationed as ambassador. Montagu’s letters back to England often contained references to the Turkish use of floral symbols. This included a reported custom of using flowers to send secret messages in the harem.

Lady Mary Wortley Montagu

THE FIRST FLORAL DICTIONARY

It wasn’t until Queen Victoria ascended the throne in the next century, however, that Montagu’s efforts to promote floriography were finally embraced. Seemingly overnight, books about flower symbolism began to be published. Many of these works continue to form the basis of the floral language we practice today.

The first dictionary to associate flowers with symbolic definitions appeared in 1819 with the publishing of Le Langage des Fleurs, a work attributed to Charlotte de la Tour. The author’s true identity remained a mystery for several years until it was revealed to be Louise Cortambert, wife of the geographer Euguen Cortambert (1805-1881). She would have been in her late thirties at the time.

1920 edition of Charlotte de la Tour’s Le Langage des Fleurs

Organized by season, Le Langage de Fleurs contained illustrations and essays on different plants along with their associated meaning. There were 330 different types of emotions. Listed in alphabetical order, they ranged from messages of love, acceptance and refusal to more specific feelings or psychological states such as Render Me Justice, My Regrets Accompany You to the Grave and the catchy Better to Die than Lose One’s Innocence. The book can still be purchased on Amazon today.

COMMON FLOWERS AND THEIR MEANINGS

So what are some common flowers that we Americans know how to read? Maybe some of these generally accepted meanings will jar your memory.

BUTTERCUPS

Remember putting a buttercup under your chin and asking your friend if it gave a yellow glow? If a yellow reflection can be seen, a person is supposed to love butter.

Buttercups can tell if you like butter

DAISIES

Or did you ever pluck off the petals of a daisy one by one while alternately repeating the phrases She Loves Me, She Loves Me Not? A game of French origin, this practice can determine if the object of your affection returns those feelings.

Reading the daisy can tell you whether or not your affections are returned

DAFFODILS

Emerging from the cold ground in early spring, daffodils are the quintessential symbol of spring and rebirth. In the language of flowers, they can also mean Regards, while some dictionaries associate them with Chivalry. Other interpretations link daffodils with self-esteem, and the Greek legend of Narcissus suggests the flowers could also represent egotism and vanity.

Daffodils symbolize spring and also regards

FORGET-ME-NOTS

Forget-me-nots’ meaning is implied in the name. The true blue flower whose Greek name myosotis means mouse ear, is commonly associated with constancy and friendship.

Forget-me-nots symbolize friendship and constancy

MIMOSA

Often flower meaning derives from the behavior of the plants itself. For instance, Mimosa pudica is often linked to sensitivity or chastity, as its leaves fold up when touched by another organism.

Mimosa pudica symbolizes sensitivity

ROSES

Even within the same species, colors can mean different things. In paintings, a deep red rose has been used for centuries to symbolize the blood of Christ, while also expressing the intensity of romantic love.

A red rose is associated with strong feelings of love

While pink roses express affection.

Pink roses represent affection

And yellow roses stand for friendship or devotion.

A yellow rose signifies friendship

Overachievers may like to emulate Felix in Honoré de Balzac’s The Lily of the Valley and compose elaborate bouquets built upon multiple meanings. In the novel, he uses flower arrangements to convey coded messages that only his lover can decipher. This took some advanced study, however, with Felix spending days in the countryside meditating on the essence of each flower.

Regardless of your flower knowledge, the list is as long as there are flower species. And though meanings may vary across cultures, the roots of this ancient custom remain the same. Some feelings are just better expressed when spoken in the Language of Flowers.

 

Bamboo Gets A Makeover Thanks To A California Garden

The Bamboo Garden at Northern California’s Foothill College

I’ll admit, I’m not a huge fan of bamboo, especially the kind that advances a foot a day and needs to be dug out with a tractor. But I was pleasantly surprised this week to have my views suddenly upended. It all started with some aqua stems I spied growing in my sister-in-law’s garden. Continue reading

Dreamy Dahlias: 10 Ways To Identify Your Perfect Type

A cactus dahlia blooming in my garden

Fall may be poking a tentative finger into my garden, but my dahlias still think it’s summer. Every morning I wake up to a multitude of new blooms. And, no matter how many I harvest, the next day there are still more waiting to be cut. In other words, October brings breakfast with an armload of fresh flowers whose brilliant, flat-tipped petals are still wet with the morning dew. Continue reading

Having A Ball With Alliums (Ornamental Onions)

Allium giganteum, also known as Giant Onion 

They look like they’ve jumped out of a Dr. Zeus book — giant purple balls stuck like lollipops on long flexible stems. Alliums can be a bit startling the first time you encounter them. But there’s so much to love about these drought tolerant plants, like long bloom period and resistance to most pests and diseases. And, their whimsical appeal is a sure-fire way to liven up your garden. Continue reading

Top Plants for Creating A Year-Round Fragrant Garden

Rose pink

(Updated February 2019)

Years ago, I was visiting Peru in December when suddenly, a sweet perfume came floating across the warm afternoon air. For a moment I was taken aback. Then I realized the smell was none other than the scent of roses. And, rounding the corner there they were; cherry-red, velvety blooms beckoning me into their fragrant garden. Continue reading