Classic British and French Garden elements.

Knot Gardens and Parterres.

Hard to say one without the other being mention, as they are both interchangeable.

The formal descriptions and definitions below.

What is a Parterre?

: Image from Google.

What is a Knot Garden?

: Image from Google.

Examples by @shadowofthegardener

North Brook House Knot Garden

Click here to Contact #SOTG about this.

A staple feature of gardens big and small up and down the country.

Simple in design through to extensive and impressive complexity.

Being both a feature and a backdrop when scaled up or spread out across the land.

While also being delicate and elegant when used in small spaces, helping to define cloisters and courtyards.

Or when surrounding Lawns or Formal Gardens.

A feature well versed in being crafted to house herb gardens as well as flower arrangements.

Box, Lonicera or Yew Hedges?

Box Hedges are the most common material used for Knot and Parterre Gardens.

Though does suffer issues with Box Blight.

So we advise using Lonicera Lonicera Nitida hedging for this.

As Yew has high levels of toxicity and can be harmful to humans, pets and cattle.

: Image by Google.

: Image by Google.

: Image by Google.

: Image by Google.

Box Blight?

: Image by Google.

Box blight can be the bane of many gardeners and Ornamental feature owners; especially in prolonged wet weather and years with higher than average rainfall. It can decimate a feature or hedge if not caught early & treated properly.

Even repairing a small section can ruin a lovely feature for years.

Or detract from a stunning feature; for along time till it has regrown or been repaired or replaced.

It can also be time intensive to treat, tend and retrain.

Box blight

Box blight, also known as boxwood blight, is a serious fungal disease that affects plants in the Buxus genus, commonly known as box or boxwood. These plants are widely used in formal gardens, such as parterres and knot gardens (as discussed earlier), for hedging, topiary, and ornamental borders due to their dense, evergreen foliage and ability to be tightly clipped. Box blight can devastate these plants, leading to significant aesthetic and economic damage in both private gardens and commercial nurseries. Let’s dive into the details:

What Causes Box Blight?

Box blight is primarily caused by two species of fungi:
Cylindrocladium buxicola (also known as Calonectria pseudonaviculata): This is the most common and widespread cause of box blight, particularly in Europe, North America, and parts of Asia.

Pseudonectria buxi (less common): This species typically causes a milder form of blight and is less destructive.

The fungus thrives in warm, humid conditions, making it particularly problematic in wet summers or regions with high rainfall. It spreads through spores that are carried by water splash (rain, overhead watering), wind, contaminated tools, clothing, or even infected plant material.

Symptoms of Box Blight

Identifying box blight early is crucial for managing its spread. Look for these signs:
Leaf Spots: Small, dark brown to black spots appear on the leaves, often with a yellow halo around them. These spots can merge, causing larger areas of dead tissue.

Leaf Drop: Infected leaves turn brown or straw-coloured and drop prematurely, often leaving bare stems.

Black Streaks on Stems: Dark, blackish streaks or lesions appear on young stems, particularly near the base of the plant.

Dieback: Whole sections of the plant may die back, starting with the lower branches, giving the plant a patchy, unhealthy appearance.

White Spore Coatings: In humid conditions, you might see white, powdery spore masses on the undersides of leaves or on stems, which is the fungus producing more spores.

Note: Young plants or new growth are particularly susceptible, and the disease can spread rapidly in dense plantings where air circulation is poor.

Conditions That Favour Box Blight

Temperature: The fungus thrives between 15°C and 30°C (59°F to 86°F), with optimal growth around 25°C (77°F).

Moisture: Wet foliage, high humidity, or prolonged leaf wetness (e.g., from overhead watering) encourages spore germination and infection.

Poor Air Circulation: Dense, unpruned box hedges or topiaries where air can’t flow freely create a microclimate that favours the fungus.

Plant Stress: Box plants that are already stressed (e.g., from drought, poor soil, or nutrient deficiency) are more vulnerable.

Impact

Box blight can be devastating:
Aesthetic Damage: In formal gardens, where box plants are often the backbone of the design (like in knot gardens or parterres), the disease ruins the clean lines and symmetry.

Economic Loss: Nurseries and landscapers suffer significant losses due to infected stock, and replacing established hedging in historic gardens can be costly.

Historical Gardens: Many historic estates, such as those in the UK (e.g., Hampton Court Palace), have struggled with box blight, sometimes leading to the removal of entire plantings.

Management and Control

Unfortunately, there’s no cure for box blight once it takes hold, but you can manage it through prevention, cultural practices, and, in some cases, chemical controls. Here’s how:

1. Cultural Practices

Improve Air Circulation: Prune box plants to allow better airflow, reducing humidity around the foliage. Avoid dense, overcrowded planting.

Watering Practices: Water at the base of the plant rather than overhead to keep foliage dry. Water early in the day so any splashed water can dry quickly.

Sanitation: Remove and destroy fallen leaves and infected plant material (don’t compost it, as the fungus can survive). Disinfect tools, boots, and clothing after working with infected plants to prevent spread.

Avoid Stress: Keep plants healthy with proper watering, mulching, and fertilization. Healthy plants are more resistant to infection.

Monitor New Plants: Quarantine new box plants for at least a month before introducing them to your garden to ensure they’re disease-free.

2. Chemical Control

Fungicides: Some fungicides can help prevent infection, but they won’t cure an already infected plant. Common options include:
Tebuconazole or trifloxystrobin: These systemic fungicides can protect healthy plants if applied before infection or at the first sign of disease.

Chlorothalonil: A protectant fungicide that can be used preventatively.

Application: Spray thoroughly, ensuring coverage of all foliage, and repeat as directed (often every 14–28 days during high-risk periods like wet summers).

Note: Fungicides are more effective as a preventative measure. Always check local regulations, as some chemicals may be restricted (e.g., certain fungicides are banned in the EU for environmental reasons).

3. Resistant Varieties

Some boxwood varieties are more resistant to blight than others:
Buxus microphylla (e.g., ‘Faulkner’) tends to be more resistant than Buxus sempervirens (common box), which is highly susceptible.

Cultivars like ‘Green Beauty’ or ‘Justin Brouwers’ have shown better tolerance in trials.

Research continues into breeding fully resistant varieties, but none are completely immune.

4. Replacement with Alternatives

If box blight becomes unmanageable, many gardeners opt to replace box with blight-resistant alternatives for hedging or topiary:
Ilex crenata (Japanese holly): Similar small, evergreen leaves and good for clipping.

Taxus baccata (yew): Another evergreen option, though slower-growing.

Euonymus japonicus (e.g., ‘Jean Hugues’): A compact evergreen with small leaves.

Lavandula (lavender) or Santolina (cotton lavender): For smaller knot gardens, these can mimic the low-growing, clipable nature of box.

Prevention

Buy from Reputable Sources: Ensure plants come from nurseries that follow strict hygiene protocols and are certified blight-free.

Avoid High-Risk Conditions: Don’t plant box in overly shaded, damp areas where air circulation is poor.

Regular Inspections: Check plants frequently, especially during warm, wet weather, to catch early signs of infection.

Historical Context and Modern Challenges

Box blight was first identified in the UK in the mid-1990s and has since spread globally, affecting gardens in North America (first reported in 2011), New Zealand, and beyond. Its rise has been linked to the global trade in ornamental plants, which facilitates the spread of pathogens. Historic gardens, like those at the National Trust properties in the UK, have had to adapt by replacing box with alternatives or trialing resistant varieties. For example, the famous box parterres at Cliveden in England were hit hard by blight in the early 2000s, leading to a shift toward other hedging plants.

Fun Fact

The fungus Cylindrocladium buxicola can survive in soil or plant debris for up to 6 years, making thorough cleanup essential to prevent reinfection.
If you’re dealing with box blight in a specific garden (like the knot garden your dog might be running near in the snowy photo you shared earlier!), let me know, and I can tailor advice to your situation. Alternatively, if you’d like an image of what box blight looks like on a plant, I can generate one—just confirm!