THE ISSUES WITH BOXWOOD

Design and InstallationGarden Caregarden TriviaIndoor plantsPlant Health CareUncategorized

Sep 15

So…. you want to plant some Boxwoods...

Endless fields of Boxwood

A GOOD choice for a hedge or even as a stand alone plant ! Just know - they are NOT an install it and forget it plant.All species are affected by several insects and diseases. Some of which might decimate the plant if not acted upon quickly. Boxwood require a lot of constant observation and follow up Insect and Disease Control - probably for the rest of the time they are in your garden.Of course you could be lucky and they might not get anything ! – but the odds are not in your favor.

THE DREADED INSECTS

Even in the best of situations, the Boxwood Leaf Miner, Boxwood Sucker, and Boxwood Leaf Hopper insects tend to appear every season.If the plant is stressed, it may also become prone to Andromeda Lace Bug and Spider Mites too! Stresses including low light, winter exposure, wet soil, or even summer heat. All affect insect infestations.Any one of these bug attacks can cause enough damage to leaves that the plant quickly becomes unattractive. In heavy populations, they will suck out so much sap there is very little sugar left over for a plant to maintain itself. Plants may succumb to other insects or diseases or be unable to survive the heat of summer or the cold of winter.

Boxwood Tree Moth

Boxwood moth caterpillars

The U.S.D.A. confirmed the presence of box tree moth (Cydalima perspectalis) in New York. The moths are likely from a nearby infestation in Canada. The insect is native to East Asia and has become a serious invasive pest in Europe and Canada, where it continues to spread.

Totally defoliated !

This moth’s caterpillars can significantly damage and potentially kill boxwood (Buxus species) plants if left unchecked. They feed quickly and heavy infestations can defoliate host plants. Once the leaves are gone, larvae consume the bark, leading to girdling and plant death.Several (3-5) treatments are required to eliminate the infestation. The moth may return every year.

Boxwood Leaf Miner

In Spring, Leaf Miners emerge as bright orange midges from last years infected leaves. These quickly mate and the females deposit eggs inside new leaves using a long ovipositor. This all happens in a just a few days !The eggs hatch as larvae inside the leaf eating it over the entire summer season and forming "blisters" visible on the leaf. During Fall, they pupate and stay inside the leaf over the winter.

Blisters blisters everywhere !

Foliar applications of pesticides do very little to kill off the larvae after the eggs hatch inside the leaves. The best treatment is using a synthetic systemic pesticide application in Spring and Fall.Midges can be sprayed with any horticultural oil or soap and are easily killed off – but timing the emergence is the difficulty. The window for treating midgets is less than a week!

Boxwood Leaf Sucker

The Boxwood Sucker shows up in early spring causing the growing tips to curl and ball up like a little cabbage. The nymphs inside the ball emerge, become adults and lay eggs on new shoot tips, continuing this cycle until late summer. These overwinter and start the process over again the following season.

Boxwood Leaf Hopper

The Leaf Hopper arrives last in mid summer but stays until fall. These lays eggs, which hatch and become adults within weeks repeating this cycle until it gets cooler.They are well known for jumping long distances when disturbed and can multiply into the THOUSANDS in a few weeks. The look like mini grasshoppers.

Leaf hopper

Andromeda Lacewing

Semi transparent adults with hourglass wings suck out sap from leaves, deposit eggs and leave plenty of tell tale black poop on the underside of leaves. They also make leaves turn pale or yellowish making for an unsightly plant.

Transparent winged Adult, juvenile nymph, and poop everywhere !

Spider Mites

Adult

From one female in spring you will have millions by July. They pierce leaves and suck out their contents leaving brown dots everywhere. This stippling is not only unsightly but an opening for disease to enter the plant.

Adults and eggs on underside of leaf

In advanced cases you will see leaves covered in fine parallel webbing. Leaves are left empty of all chlorophyll making them yellowish pale. These soon fall off.

Webbing is a high population symptom !

THE DREADED DISEASES

Even in the best circumstances and with the best care, Boxwood may get a disease. Fortunately, they rarely get any Viral diseases - but the three main fungal diseases they do get are very serious and can cause a lot of damage or even kill the plant.Contamination occurs from fungal spores entering the tissues via cuts or lesions, and through leaf pores and lenticels on the trunks. Infection sources can be up to 1 mile away and are readily carried by the wind. They affect all know species and cultivars of Boxwood and are most active during the Spring and Fall, preferring cooler moist seasons.The three main disease causing funguses are; Boxwood Blight caused by Cylindrocladium pseudonaviculatum, Boxwood leaf spot (Macrophoma candollei) and Volutella.All the leaf debris will contain the fungal spores, so careful removal of all leaf litter, mulches or damaged tissues is essential. Severely affected plants should be isolated or replaced.In addition to cleaning and replacement, all affected AND adjacent Boxwood should be treated with a strong fungicide several times during both of the cool weather seasons.

Boxwood Blight

Cornell University issued warnings about an aggressive, quick moving disease causing dramatic defoliation and death in Boxwood species in the eastern US. Symptoms include round brown leaf spots, tip lesions, and a quick progression to full defoliation, usually within 7 days.

Total defoliation is an understatement ...

The disease is caused by a fungus introduced from Europe – Cylindrocladium pseudonaviculatum. It affects all know species of Boxwood and is most active during cooler moist seasons.Some botanical gardens have been able to achieve almost 100% protection by using a combination of three fungicides every 2 weeks during cool wet seasons, including plants sprayed prior to or after shearing. The additional application of a phosphate soil additive and/or a magnesium compound is also recommended.The fungicide treatment will NOT kill the fungus, only the fungal spores that land on the plant. Spraying is preventative and good only for reducing the risk of getting the disease.Once the plant has the disease there is no way to eradicate it from the tissue. New cultivars are being developed to have strong immunity to this disease.

Boxwood Leaf Spot and Volutella

These two diseases usually only strike as a result of something else previously stressing the plant - they are opportunistic in that way. They do however weaken the plants further and should be dealt with quickly.Extremes of heat and cold, winter damage, root bound plants and irrigation issues are some examples of possible stresses.

Volutella: leaf turns Tan and papery

Macrophoma: small black spots on underside of leaf

Boxwood are definitely not low maintenance despite everyone believing so. But if you are diligent in your observations and prepared to treat quickly they are a great resource for evergreen hedges in most light situations.

Our Plant Health Care Team has year round treatment plans to keep all of these in check !

Call us - let's talk Boxwoods !

PLANT SPECIALISTSGREENING NEW YORK FOR OVER 53 YEARS !

Article written by our Staff Horticulturist, Peter B Morris, BSc, MSc, MBAAll photographs used with permission @SHUTTERSTOCK

Peter Morris

Peter was born and raised on a beautiful green island in the midst of a tropical rainforest. He was introduced into the world of plants at the age of six when his grandmother, an avid Spanish gardener herself, asked him to help her grow seeds for her pepper garden. He was hooked! By the time he was a teen, he had his own rose and orchid collection numbering in the hundreds. Botany was in his blood, and that is what he set out to study.

His passion brought him to NY in the late seventies to further his education. His tenacity allowed him to work full time at Plant Specialists while he completed a MS in Plant Biology. As a manager at the time he felt unsatisfied with his knowledge of business and business processes. Peter felt compelled to learn, so he then pursued and completed an MBA in Quality Management within a few short years.

Peter’s other passion is teaching. His natural ability is quickly consumed by our staff in all subjects in Botany, Horticulture, and Landscaping. He created an immense reference library of more than 3,500 plants providing an invaluable resource for our staff.

Peter’s breadth of knowledge and wisdom allows him to effectively diagnose the needs of plants. Sometimes just by walking into a garden he can create a prescription that fixes even the hardest issue. He is our Staff Botanist, Diagnostician, and all around Mentor. Recently, he has put his immense knowledge and skills into developing a new department that focuses on Plant Healthcare. As he puts it, “Magic through Science”. The PHC staff that surround him have avidly consumed his teachings. Substantially developing their own plant wisdom, many have taken on difficult plant health issues with spectacular results.

Plant Healthcare has been an instant success with customers! The proper treatment of insects and diseases including Organic methods has made pest control a necessity for every plant. Correcting hormonal imbalances caused by planting in containers or refurbishing soils leached of nutrients by irrigation systems are big challenges PHC has become quite comfortable addressing. The scientific approach to the complex demands of keeping plants healthy in our harsh city environment has made many a customer say WOW!

THE ISSUES WITH BOXWOOD

So…. you want to plant some Boxwoods...