Ajuga reptans

Plant Profile & Key Characteristics

Overview: Ajuga reptans (Bugleweed) is a low, spreading evergreen to semi-deciduous perennial groundcover 10-25 cm (4-10 in) tall, with colourful leaf rosettes. It spreads quickly by runners and sends up short spikes of purple or blue flowers, thriving in temperate climates and shade.

Quick Specifications

Specification	Attribute
Plant Type / Life Cycle	Perennial (herbaceous groundcover)
Foliage Type	Evergreen to semi-deciduous
Mature Size	Foliage 10-25 cm (4-10 in); flower spikes 30-40 cm (12-16 in)
Growth Rate	Fast
Root System	Shallow and stoloniferous (spreads by runners); can be invasive
Hardiness	USDA zones 3-9

Growth Form & Structure

• Height & Spread: Mat-forming foliage 10-25 cm (4-10 in) tall with flower stalks 30-40 cm (12-16 in); spreads horizontally by stolons and is also suited to containers.
• Growth Habit & Form: Low, creeping groundcover forming dense mats of leaf rosettes.
• Lifespan & Maturity: Long-lived perennial that establishes and spreads quickly – trim to control its horizontal spread.

Anatomy & Physical Features

• Leaves & Foliage: Rosette leaves in blue, bronze, purple, red, pink or green, ovate to heart-shaped and sometimes serrated.
• Flower Characteristics: Purple or blue flowers in short, upright spikes (full detail in the Bloom accordion).

Primary Uses & Landscape Value

• Functional & Ornamental Roles: Groundcover, edging, shade and underplanting, erosion control, and container plant.

Care Guide: Planting, Soil & Watering

Overview: This fast-spreading evergreen groundcover suits cooler temperate gardens in full sun to full shade. It likes well-drained but moisture-retentive soil and struggles in hot climates.

Quick Care Requirements

Requirement	Ideal Condition
Planting Season	Spring, summer or autumn
Growth Rate	Fast
Soil Type	Well-draining yet moisture-retentive
Water Need	Moderate — keep the soil evenly moist

Planting & Establishment

• Best Planting Season: Plant in spring, summer or autumn while the soil is workable; avoid the peak of summer heat, which it dislikes.
• How to Plant:
  • Hole Preparation: Dig holes just wider than each small root ball and space the plants so they knit into a carpet.
  • Soil Amendments: Mix in compost to hold moisture while keeping the soil free-draining.
  • Planting Depth: Set the crown level with the soil surface so the rosette is not buried.
• Growth Speed & Expectations: Fast — it spreads vigorously by stolons into dense groundcover, so allow room or trim it to contain the spread.

Soil, Watering & Drainage Care

• Soil Mix & Drainage Needs: Well-drained soil that still holds some moisture; in containers use a quality mix with drainage holes.
• Watering Schedule & Technique:
  • Young / Newly Planted: Keep the soil consistently moist while plants establish and spread.
  • Established: Average, even watering; do not let it bake dry, especially in sun.
  • Seasonal Adjustments: Water more in summer heat (it resents drought and hot spells) and less in cool, damp weather.

Climate, Light & Hardiness

Ajuga reptans (Bugleweed) is a very cold-hardy, mat-forming temperate groundcover, thriving in cool climates in anything from full sun to full shade. Per site data it is hardy in zones 3–9, and summer heat - not cold - is its limiting factor.

Quick Climate Specifications

Climate Zones	Cool to warm temperate
USDA Hardiness Zones	3–9 (site data)
Approx. Survival Minimum	Established plants survive zone 3 winters (roughly −40 °C / −40 °F)
Frost Tolerance	High
Light Conditions	Full sun to full shade (with some light)
Wind Tolerance	High (low, ground-hugging habit)

Sunlight & Light Exposure

Optimal Light Setup

Extremely adaptable, from full sun to full shade. Rich leaf colour is strongest in brighter positions, while shade keeps it cooler and greener.

Shade & Heat Management

In hot-summer regions part to full shade is valuable: the site data notes this plant is not tolerant of hot climates, and shade with steady moisture reduces heat stress and scorch.

Best Exposure / Orientation

A cool, lightly shaded aspect with well-drained but moist soil suits it best where summers are warm.

Temperature Extremes & Hardiness

USDA Hardiness & Regional Limits

Site data gives zones 3–9. The low end reflects excellent winter-cold survival; the warm end (about zone 9) is set by summer heat, as the plant dislikes hot climates.

Cold Damage & Winter Protection

Reliably winter-hardy through its range and generally needing no protection; it may go semi-deciduous in the coldest winters and flush again in spring.

Frost Sensitivity

Very low - evergreen to semi-evergreen and untroubled by ordinary frost.

Extreme Heat Tolerance

Low. Hot, humid conditions stress the foliage and can lead to crown rot; this is the practical limit on where it grows well, so give it shade and airflow in warm climates.

Wind, Humidity & Microclimate

Humidity Preferences

Prefers moderate humidity with good air movement; stagnant, hot, humid air encourages rot.

Wind Tolerance

High - its low, ground-hugging mat is unaffected by wind.

Rainfall & Seasonal Moisture

Adapted to evenly moist temperate conditions on well-drained ground; it dislikes both drought and waterlogging.

Microclimate Recommendations

In warm regions plant it in a cooler, part-shaded spot with free-draining soil and good airflow to offset its poor heat tolerance.

Growing in Pots, Balconies & Indoors

Ajuga reptans (bugleweed) is a low, spreading evergreen groundcover, and the grower confirms it grows both indoors and in containers. Its neat carpet of glossy, often colourful leaves and short spikes of blue flowers make it an easy, adaptable plant for pots, edges and even a bright indoor spot.

Quick Details

• Container Size: A shallow, wide pot (about 3-8 L / 1-2 gal) suits its spreading, shallow roots
• Indoor Suitability: Suitable indoors per the grower – give it a bright spot; it tolerates shade but keeps its colour best in good light
• Best Spot: Full sun to full shade (with light); leaf colour is richest in brighter positions
• Soil & Drainage: Ordinary, free-draining potting mix; it is not fussy
• Watering in Pots: Average – keep lightly moist; it dislikes both drought and waterlogging

Indoors & On the Windowsill

• An easy indoor groundcover: The grower marks it suitable indoors. Set it near a bright window; in a hanging pot or bowl it spills attractively over the edge.
• Light & colour: It survives in shade, but the coloured-leaf forms stay brightest with plenty of light.
• Watch its spread: It roots as it runs, so a contained pot keeps it tidy indoors.

On a Balcony or Patio

• A tough edging & filler: Great around the base of larger pots or as a spreading carpet in a trough; sun or shade both work.
• Even moisture: Its shallow roots dry out fast in a pot – keep the mix lightly and evenly moist, especially in sun.

Choosing the Pot, Soil & Long-Term Care

• Pot & drainage: Wide and shallow with good drainage holes; skip a standing saucer to avoid rot.
• Potting mix: Ordinary free-draining potting mix with some organic matter.
• Feeding: Light and occasional through the growing season – too much feed makes it leggy.
• Repotting & dividing: Every couple of years lift, divide and replant the spreading clumps into fresh mix.

Fertilizing & Feeding

A light feeder: a little balanced feeding through the active growing season plus organic matter is plenty, with feeding eased off while growth is slow.

Quick Fertilizing Specs

Feeding Level	Light feeder
Main Nutrient Priority	Balanced feeding with adequate nitrogen for foliage
Best Feeding Period	Spring through the warm active growing season
Organic Options	Compost, humus, and other organic matter
Reduce/Stop Feeding	Ease off through cool weather and winter dormancy
Micronutrients	Usually supplied by organic matter and a complete fertilizer; correct only diagnosed problems
Soil pH	Slightly acidic to near neutral

Feeding by Growth Stage

Spring flush of growth

Support the flush of new growth as the plant wakes in spring.

Nutrient direction	A balanced complete fertilizer with adequate nitrogen to fuel fresh foliage.
Timing	As growth resumes in spring.
Frequency	A light feeding as active growth begins.
Fertilizer types	A balanced complete fertilizer, Compost or other organic matter worked in
Precautions	Keep feeding light; rich soil and organic matter do much of the work.

Active season growth

Maintain steady, healthy growth through the season.

Nutrient direction	Occasional light balanced feeding keeps growth steady without forcing soft growth.
Timing	Through the warm active growing season.
Frequency	Occasional light feeding, with organic matter renewed as needed.
Fertilizer types	A balanced complete fertilizer, Compost or humus as a top-dressing
Precautions	Avoid overfeeding, which produces lush growth prone to disease and flopping.

Cool-season rest or dormancy

Let the plant rest through cool weather without pushing new growth.

Nutrient direction	None – withhold fertilizer while the plant is not actively growing.
Timing	During cool weather, dormancy, or winter dieback.
Frequency	No feeding during this rest; resume only when active growth returns.
Fertilizer types	No feeding at this stage; hold off fertilizing until active growth resumes.
Precautions	Do not fertilize a resting plant; feeding now wastes nutrients and risks salt buildup.

Nutrient Deficiency Signs & Corrections

Older, lower leaves fade to pale green or uniform yellow and overall growth slows.

Possible causes	low available soil nitrogen, nitrogen leaching from heavy watering or rain, thin soil low in organic matter
Appears first on	older, lower leaves
What to check	recent feeding history, soil organic matter, watering and drainage
Possible correction	Apply a nitrogen-containing complete fertilizer and build soil organic matter, then water evenly.

Youngest leaves yellow between the veins while the veins themselves stay green.

Possible causes	high soil pH reducing iron and manganese availability, waterlogged or poorly drained roots, genuinely low micronutrient supply
Appears first on	new, young leaves
What to check	soil pH and drainage, watering habits, whether symptoms are on the newest growth
Possible correction	Correct soil pH if high, improve drainage, and apply a chelated iron or manganese product per its label.

Leaf margins brown or scorch and growth stalls despite adequate watering.

Possible causes	fertilizer salt buildup in the root zone, under-watering that concentrates salts, excessive or too-frequent feeding
Appears first on	leaf margins and tips
What to check	recent fertilizer amounts, watering consistency, drainage, especially in containers
Possible correction	Ease off feeding, water thoroughly to flush accumulated salts, then return to lighter feeding.

Pruning, Training & Seasonal Maintenance

Ajuga reptans (Bugleweed) is a low, mat-forming evergreen groundcover that spreads by creeping stolons, not by woody stems — and unlike most perennials here it genuinely tolerates and benefits from shearing. The two real jobs are shearing off the spent flower spikes after the spring–summer bloom and trimming or removing runners to control its vigorous, potentially invasive horizontal spread. A congested or tired mat can simply be sheared over to rejuvenate it. Flowers form fresh each spring on short spikes, so shearing them off costs no future bloom.

Quick Pruning & Maintenance Specs

Pruning Tolerance	Moderate — the mat tolerates shearing and even mowing on a high setting
Primary Pruning Window	After flowering (late spring–summer) — shear off spent flower spikes
Secondary Maintenance Window	Through the growing season — trim or pull runners to contain spread
Typical Frequency	One or two shearings a year plus edge control as needed
Main Objective	Deadhead spikes, control spread, and renew a tired mat
Young Plant Priority	Let the stolons root and knit together — minimal cutting
Mature Plant Priority	Contain runners, deadhead, and shear a congested mat to rejuvenate
Best Tool Type	Hedge or grass shears for the mat; a border spade for severing runners
Avoid Heavy Pruning During	Peak summer heat and drought — hard shearing then browns the mat

Pruning by Plant Age & Size

Newly Established

Let the young plants send out stolons and knit into a mat; remove only damaged growth. Establishment is about coverage, not cutting.

Young / Formative

No structural training — it is a spreading mat, not a branched plant. The ‘formative’ work is directional: start trimming runners at the edges to keep the drift where you want it.

Mature / Established

Deadhead the spent spikes, sever and remove escaping runners to contain the invasive spread, and when the mat grows congested or develops bare or rotten centres, shear the whole planting to rejuvenate it — it regrows readily from the crowns.

Seasonal Pruning Schedule

After Flowering (Late Spring / Summer)

Objective: tidy and limit seeding. Remove: the spent flower spikes by shearing them just above the foliage. Do NOT: shear away the low leaf mat itself unless rejuvenating. Response: a neat, dense carpet; flowering impact: none next year, as spikes form fresh each spring, and deadheading reduces unwanted self-seeding.

Growing Season (Spread Control)

Objective: containment. Remove: stolons/runners creeping into lawn or beds, cutting them at the mat edge. Do NOT: let it run unchecked — it can become invasive. Response: a defined, controlled patch.

Ongoing Sanitary

Objective: health. Remove: patches gone brown or rotten in hot, humid, still conditions. Do NOT: leave a dense soggy mat, which invites crown rot.

Special Growth to Remove

• Runners / stolons: the key control task — sever and lift the creeping stems at the mat edge to stop Ajuga invading lawn and borders.
• Spent flower spikes: shear off after bloom to tidy the mat and curb self-seeding.
• Dead or rotted patches: cut out sections lost to crown rot in humid heat and improve the airflow around them.

Structural Pruning & Training

There is no framework to train — the plant is a carpet. Its ‘renewal pruning’ is shearing: cutting the whole mat back over the crowns thins congestion, removes tired or bare centres, and forces fresh dense regrowth from the base. Spread is managed the same way runners are — by cutting at the edges.

Container & Small-Space Pruning

Growing Ajuga in a container or a hard-edged bed is itself a form of spread control, since the runners can be trimmed cleanly at the rim. Shearing to deadhead and rejuvenate works exactly as in the ground; the difference is that containment is easy, so the main task shifts from chasing runners to simple deadheading.

Tools

Because this is a true mat-forming plant, hedge or grass shears (or a mower on a high setting for large drifts) are the right tool for deadheading and rejuvenation — one of the few plants here where shearing is correct. Bypass secateurs handle spot work, and a border spade severs runners. No loppers or saw are needed.

Tool Hygiene & Disease Risk

Routine, rising to Increased where crown rot is present. In hot, humid, crowded conditions Ajuga is prone to crown and root rot; if you are cutting out affected patches, bag the material and clean the tool so you do not spread the pathogen across the mat. Ordinary deadhead shearing needs only clean tools.

Cut Placement & Technique

• Shear spent flower spikes just above the leaf mat after bloom.
• To rejuvenate, shear the whole mat to roughly 2–3 cm above the crowns so it reshoots densely.
• Sever escaping runners with a spade or shears right at the mat edge, and lift the cut stolons so they do not re-root.

Heavy Pruning & Rejuvenation

Ajuga tolerates hard shearing well — a matted, congested or partly bare planting can be sheared right down (or mown high) and it regrows a fresh, dense carpet from the crowns. This is best done in cooler, moist conditions in spring or after flowering, not in the heat of summer when a shorn mat can brown and rot.

Post-Pruning Care

After shearing, water if the weather is warm and keep good airflow around the mat to prevent crown rot — the main aftercare here is humidity/heat management, not feeding. A sheared mat greens up on its own without a nitrogen push.

Common Pruning Mistakes

• Letting runners escape into the lawn and beds — Ajuga spreads by stolons and turns invasive if not edged.
• Leaving a dense, humid, un-thinned mat that succumbs to crown rot.
• Not deadheading, so it self-seeds into unwanted places.
• Shearing hard in peak heat or drought, browning the whole carpet.

When NOT to Prune

• Avoid hard shearing during peak summer heat or drought — risk of brown-out and crown rot.
• Do not cut during establishment — let the mat knit in first.
• Hold off on major work when the soil is hot and the air is still and humid.

Recommended Tools (by task)

• hedge_shears — shearing spent flower spikes and rejuvenating a congested mat (a genuine mat-forming groundcover).
• bypass_secateurs — spot-trimming and cutting out small rotted patches.
• garden_spade — severing and lifting escaping runners at the mat edge.

Propagation Guide

Bugleweed (Ajuga reptans) is easiest to increase from the rooted plantlets carried on its creeping stolons (runners), or by dividing the spreading mat; seed is a slower alternative. Ordinary green bugleweed comes largely true from seed, but coloured-leaf selections do not, so vegetative pieces are used to keep leaf colour. It is easy — often the plant does most of the work itself.

Quick Propagation Specs

Best Propagation Method	Rooted plantlets from stolons / division of the mat
Alternative Methods	Seed
Propagation Difficulty	Easy
Seed True-to-Type	Species largely true; named leaf selections are not
Vegetative True-to-Type	Yes
Best Propagation Season	Spring to autumn

Runners & Stolons

Bugleweed spreads by above-ground stolons that root down at the nodes to form new rosettes. The simplest increase is to lift one of these plantlets once it has made its own roots, sever the connecting stolon from the parent, and replant it where wanted. Because it self-roots so readily it can become invasive, so lift and move plantlets rather than letting them run.

Division, Offsets, Pups & Suckers

An established clump can also be lifted and pulled or cut apart into several rooted rosettes in spring or autumn; replant each piece with roots attached and keep moist until it takes.

Growing from Seed

Sowing Season

Sow in spring or summer.

Sowing Depth & Orientation

Sow the fine seed shallowly, barely covered.

Germination Conditions

Keep the surface moist and in a warm, bright spot; light shade suits the seedlings, matching the plant’s tolerance of sun to full shade.

Bloom & Flower Guide

Quick Details

• Bloom Season: Spring into early summer
• Flower Appearance: Short upright spikes of small purple or blue flowers held above the leaf mat
• Edibility: Ornamental groundcover – grown for its foliage and flowers, which are not treated as a culinary flower

Detailed Blooming Overview

Bugleweed is a low, spreading groundcover that comes into its own in spring, when short spikes of little tubular flowers rise in tiers above the dense carpet of leaves. In a mass it can turn a shaded patch briefly blue-purple, and it is one of the more useful early plants for pollinators.

Flower Characteristics

• Small purple or blue flowers.
• Arranged in whorls up a short upright spike (inflorescence) above the foliage.

Bloom Care & Thinning

• Site for best bloom: Part shade to sun in moist soil gives the fullest flowering; a little sun deepens leaf colour too.
• After flowering: Shear off the spent spikes to tidy the mat and keep it looking fresh.
• Pollination: An excellent early nectar source, busy with bees.

Pests, Diseases & Troubleshooting

Overview: Bugleweed is a tough, low-maintenance groundcover with few insect enemies; its Achilles heel is crown and root rot — above all Southern blight (Sclerotium rolfsii) — which can wipe out patches in warm, humid, poorly drained conditions. Good drainage, air movement through the mat, and avoiding overhead watering in heat prevent most losses. A carpeting bugleweed groundcover; culture and problems are those of Ajuga reptans.

Quick Troubleshooting Overview

Issue / Pest	Main Symptom	Primary Solution
Crown rot / Southern blight	Sudden brown, collapsing patches; white threads and seed-like sclerotia at soil line	Improve drainage/airflow, remove infected clumps and soil
Root rot	Wilting, yellowing, blackened roots in soggy ground	Reduce watering, improve drainage, thin dense mats
Aphids	Sticky, distorted new leaves with soft insects	Hose off; insecticidal soap; encourage lady beetles
Spider mites	Fine stippling in hot, dry, stressed plantings	Raise humidity/irrigation, insecticidal soap
Powdery mildew / leaf spot	White film or brown spots on leaves in crowding/shade	Thin plants, improve airflow, remove affected leaves

Common Pests & Management

• Aphids (Aphis / Myzus spp.):
  • Symptoms: Small soft insects clustering on tender new leaves and flower spikes in spring, causing sticky honeydew, sooty mould and some leaf curl. Usually a minor, temporary problem.
  • Prevention & Control: Dislodge with a jet of water and rely on lady beetles and lacewings, which control them quickly outdoors. Use insecticidal soap only for a heavy early flush.
• Two-spotted spider mite (Tetranychus urticae):
  • Symptoms: Appears on drought-stressed plantings in hot, dry sites: leaves take on a fine pale stippling and dull bronze cast, with faint webbing when severe.
  • Prevention & Control: Keep plants adequately watered and not heat-stressed; overhead rinsing helps. Insecticidal soap or horticultural oil for bad patches.
• Root-knot nematodes (Meloidogyne spp.):
  • Symptoms: Patchy poor growth, stunting and heat-wilting in warm sandy soils, with small galls on the roots.
  • Prevention & Control: Improve soil with organic matter, avoid moving infested soil, and replant clean divisions into fresh ground. No home cure for a galled clump.
• Slugs & snails (Gastropoda):
  • Symptoms: Irregular ragged holes chewed in the leaves and silvery slime trails over the mat, worst in damp, shady conditions.
  • Prevention & Control: Hand-pick at night, remove damp hiding places, and use iron-phosphate slug bait or copper barriers around prized plantings.

Diseases & Fungal Issues

• Southern blight / crown rot (Sclerotium rolfsii (Athelia rolfsii)):
  • Symptoms: The signature killer of Ajuga. In warm, humid weather whole clumps suddenly wilt, yellow and collapse; at the soil line you find a white fan of fungal threads and tan, mustard-seed-sized sclerotia. It spreads outward through the dense mat.
  • Treatment & Management: Act fast: dig out and destroy affected plants along with the surrounding infested soil, and don’t compost them. Improve drainage, thin the planting for airflow, and avoid burying the crowns or mulching heavily against them. Space divisions and avoid overhead watering in heat; there is no reliable home chemical cure once established.
• Root & crown rot (Phytophthora / Pythium / Rhizoctonia spp.):
  • Symptoms: Wilting, yellowing and dieback of clumps in wet, heavy or poorly drained soil, with brown mushy roots and rotted crowns.
  • Treatment & Management: A cultural problem: plant in well-drained soil, don’t overwater, and divide crowded mats to keep them open. Remove rotted clumps and replant healthy divisions in better-drained ground.
• Powdery mildew & fungal leaf spot (Erysiphales / Colletotrichum spp.):
  • Symptoms: White powdery film or brown-purple leaf spots on crowded, shaded plants with poor air movement; mostly cosmetic.
  • Treatment & Management: Thin and space the planting, improve airflow, and remove affected leaves. Rarely needs spraying; sulfur or potassium bicarbonate helps if mildew is persistent.

Growing Difficulties & Abiotic Problems

• Crown rot from poor drainage & humidity:
  • Cause & Symptoms: The core weakness: dense mats in heavy, wet soil or high summer humidity keep the crowns damp and airless, inviting rot and Southern blight.
  • Correction Strategy: Plant in well-drained soil, divide clumps every few years to keep them open, avoid heavy mulch over the crowns, and water at the base in the morning so foliage dries.
• Leaf scorch in hot sun:
  • Cause & Symptoms: In hot climates full afternoon sun and dry soil brown and crisp the leaf edges, dulling the coloured foliage forms.
  • Correction Strategy: Site in part shade in hot regions, keep soil evenly moist, and mulch lightly between plants to moderate soil temperature.
• Winter desiccation & heaving:
  • Cause & Symptoms: In cold, exposed sites the semi-evergreen foliage browns from cold winds and shallow crowns can be heaved out by freeze-thaw.
  • Correction Strategy: Apply a light winter mulch after the ground freezes, firm back any heaved crowns in spring, and trim damaged foliage as growth resumes.
• Overcrowding & dieback:
  • Cause & Symptoms: Vigorous mats can grow so dense that the centres thin, brown and die out, and stagnant air fosters disease.
  • Correction Strategy: Divide and replant every two to three years, thinning to restore airflow and vigor.

What Helps — Products & Tools

This groundcover needs little more than good culture: sharp drainage and periodic division to prevent crown and Southern blight rot, insecticidal soap for the occasional aphid or mite, iron-phosphate slug bait or copper barriers for slugs and snails, and (only if mildew persists) a sulfur or potassium-bicarbonate spray. Remove and destroy rot-affected clumps rather than treating chemically. Follow the label and protect beneficial insects.

Varieties & Cultivars

• Burgundy Glow — Learn more about Burgundy Glow · Shop Burgundy Glow on Amazon
• Black Scallop — Learn more about Black Scallop · Shop Black Scallop on Amazon

Frequently Asked Questions

Is bugleweed the same as Ajuga reptans?

Yes — bugleweed is the common name for Ajuga reptans, a fast-spreading evergreen groundcover grown for its glossy, often bronze-tinted foliage and short spikes of blue-purple spring flowers.

Is Ajuga reptans (bugleweed) invasive?

It can be. Ajuga reptans has a shallow, stoloniferous root system that spreads quickly by runners, and if left unchecked it can invade lawns and beds — so runners need regular trimming or lifting to keep it contained.

Can you grow Ajuga reptans from seed?

Yes, though it’s slower than division or rooted plantlets. Sow the fine seed shallowly in spring or summer, and keep the surface moist in a warm, bright spot with light shade for germination. Ordinary green bugleweed comes largely true from seed, but coloured-leaf selections do not, so those are propagated vegetatively instead.

What is the biggest problem when growing Ajuga reptans?

Its main weakness is crown and root rot, especially Southern blight (Sclerotium rolfsii), which can suddenly wilt and collapse whole patches in warm, humid, poorly drained conditions. Good drainage, airflow through the mat, and avoiding overhead watering in heat prevent most losses.