Natural Groundcovers That Help Deter Black Garden Ants

Black garden ants are a common nuisance in many temperate gardens. They rarely damage mature plants directly, but they create unsightly nests, protect aphids and other honeydew-producing pests, and can undermine seedlings and garden structures. Choosing the right groundcovers is an effective, low-toxicity strategy to discourage ant activity while improving soil cover, biodiversity, and garden aesthetics. This article explains how and why some groundcovers deter ants, profiles the best species to consider, and gives practical planting and maintenance strategies to maximize success.

How groundcovers deter ants: mechanisms and principles

Understanding why certain groundcovers reduce ant presence helps you choose wisely for your site.

Aromatic barrier: Many groundcovers produce strong-smelling essential oils that mask pheromone trails or are outright repellent to ants (mints, thyme, rosemary family, and many Mediterranean herbs).
Dense, low mats: Groundcovers that form tight, impenetrable mats reduce the open soil space ants prefer for establishing surface runs or shallow nests (ajuga, thyme, sedum).

Unsuitable habitat: Some plants have leaf textures, surface residues, or moisture regimes that ants avoid, for example, succulent groundcovers or very wet soils are unattractive to surface-nesting ants.
Indirect control (reducing food sources): Ants farm aphids, scales, and mealybugs for honeydew. Groundcovers that do not attract these sap-suckers, or that attract predators (ladybirds, lacewings, parasitic wasps), reduce the incentive for ants to patrol an area.
Physical barriers and trap cropping: Strategic placement of pungent groundcovers as a perimeter or barrier around susceptible plants can block ant trails and redirect them away from key areas.

Best natural groundcovers that deter black garden ants

Below are reliable groundcovers, chosen for their ant-deterring qualities, ease of cultivation, and usefulness in diverse garden settings. Each entry includes growth habit, preferred conditions, the ant-deterrence mechanism, and cautions.

Creeping thyme (Thymus serpyllum, Thymus praecox)

Growth habit: Low, dense mat 1-3 inches tall, spreads 6-24 inches.
Conditions: Full sun, well-drained soil; drought tolerant.
How it deters ants: Strong aromatic oils mask trails and repel ants; dense mats close off soil surfaces.

Notes: Excellent between pavers and in rock gardens; tolerates light foot traffic.
Woolly thyme (Thymus pseudolanuginosus)
Growth habit: Very low, soft mat 0.5-1 inch high; spreads widely.

Conditions: Full sun to part shade; well-drained soil.
How it deters ants: Same aromatic defense as other thymes; forms thick carpet that discourages surface nesting.
Notes: Noninvasive and decorative.

Creeping rosemary (Rosmarinus officinalis ‘Prostratus’ or Salvia rosmarinus prostratus)
Growth habit: Prostrate woody branches that form evergreen groundcover.
Conditions: Full sun, well-drained soil; Mediterranean climates thrive.

How it deters ants: Strong resinous oils repel many insects and mask chemical trails.
Notes: Cold tolerance varies by cultivar; deer tend to avoid it.
Oregano and marjoram (Origanum vulgare and Origanum majorana)

Growth habit: Low, spreading clumps 6-12 inches tall.
Conditions: Full sun to light shade; well-drained soils.
How it deters ants: Aromatic oils discourage ants and other pests; dense growth reduces habitat.

Notes: Can be semi-aggressive; good in herb gardens and mixed borders.
Lavender (Lavandula angustifolia varieties, low cultivars)
Growth habit: Low woody mat in dwarf varieties, 6-12 inches tall.

Conditions: Full sun; poor, rocky soil acceptable; excellent drainage required.
How it deters ants: Strong fragrance and essential oils mask pheromone trails and repel many insects.
Notes: Choose low cultivars if you need groundcover effect.

Pennyroyal and some mints (Mentha pulegium and Mentha spp.)
Growth habit: Spreading runners, forms dense cover.
Conditions: Part shade to sun; moist to average soils.

How it deters ants: Powerful mint oils are generally offensive to ants.
Notes: Highly invasive; pennyroyal is toxic to pets and humans in concentrated forms. Use containers or root barriers, and consider safer mint relatives.
Ajuga (Ajuga reptans)

Growth habit: Fast-spreading evergreen rosettes, 2-6 inches tall, forms a mat.
Conditions: Part shade to full sun (depending on cultivar); average soil.
How it deters ants: Not strongly aromatic, but the dense, low mat disrupts ant trails and surface nesting.

Notes: Good for shade; can self-seed and become dominant in moist soils.
Sedum (Sedum spurium and other low sedums)
Growth habit: Succulent, low mats 1-4 inches tall.

Conditions: Full sun; excellent drainage; drought tolerant.
How it deters ants: Succulent leaf surfaces and open, stony habitats are less attractive to ants; also good between rocks where ants avoid exposed conditions.
Notes: Excellent for rock gardens and hot, dry spots.

Santolina (Santolina chamaecyparissus)
Growth habit: Low, mounded evergreen shrub to 1-2 feet, can be used as groundcover in drifts.
Conditions: Full sun, very well-drained soil.

How it deters ants: Strong resinous scent is repellant; textures and oils discourage surface activity.
Notes: Attractive silver foliage; can be pruned into low hedges or massed.
Rue (Ruta graveolens), use with caution

Growth habit: Openly mounded, 1-2 feet tall.
Conditions: Full sun to light shade; well-drained soil.
How it deters ants: Pungent aromatic compounds repel many insects.

Notes: Can cause skin irritation and photodermatitis in sensitive people; avoid if you have pets or children who contact plants frequently.

Practical planting strategies to maximize ant resistance

Selecting the right species is only part of the solution. How you plant and maintain groundcovers will determine whether ants move elsewhere or simply nest beneath the plants.

Create barrier bands around vulnerable plants and structures.
Plant strips of aromatic groundcovers (thyme, rosemary, lavender) several feet wide around vegetable beds, fruit trees, or foundations to mask scent trails and create a behavioral barrier for ants.
Mix species for resilience.

Combine a strongly aromatic species (e.g., thyme) with a dense non-aromatic mat (e.g., ajuga or sedum) to get fragrance plus physical coverage. Diversity also reduces the chance a pest will find a hospitable host.
Remove honeydew sources.
Inspect shrubs and nearby plants for aphids, scale, or mealybugs. Ants will aggressively protect colonies of these pests. Control the sap-suckers by pruning, blasting with water, or introducing predatory insects, and ant pressure will drop.

Use gravel or coarse mulch edges.
Ants are less likely to nest in areas with coarse, rocky mulch or crushed stone. A narrow strip of gravel between turf and plantings in combination with aromatic groundcovers creates a double deterrent.
Avoid excessive thatch and organic mulch right next to structures.

Thick wood-chip mulch next to foundations is attractive to ants for nesting. Keep mulch pulled back and prefer low-maintenance groundcovers next to buildings.
Maintain good air circulation and avoid overwatering.
Many ant species prefer dry, well-drained nest sites but will exploit warm, moist microhabitats if they exist. Overly humid, densely mulched beds can encourage nesting and pest insects that attract ants.

Maintenance tips and cautions

Prune back mats regularly. Dense thatch can sometimes create inviting space for queens to start nests if it becomes overly thick and undisturbed.
Monitor for invasiveness. Mints, pennyroyal, and some ajuga strains can be aggressive. Use root barriers, plant in containers, or select sterile cultivars where available.
Mind pets and children. Some effective repellant plants (pennyroyal, rue) are toxic or cause skin irritation. Avoid planting these in high-contact play areas.

Replace problem species. If an area still attracts ants despite groundcover, look for aphid-infested nearby ornamentals or hidden food sources (pet food, compost). Removing the attractant is often more effective than adding barriers.
Use voluntary biological control. Encourage birds and beneficial insects by including native wildflowers and leaving some sheltered spots for predatory insects. A healthy predator community reduces honeydew producers.

Quick decision guide by site condition

Full sun, hot, dry: Creeping thyme, low lavender cultivars, sedum, santolina.

Part shade, moderate moisture: Ajuga, woolly thyme (in sunnier parts), low oregano varieties.
Moist sites: Select less drought-tolerant mints with caution (contain them), or use ajuga and densely planted native groundcovers that do not attract aphids.
Between pavers and footpaths: Creeping thyme and woolly thyme for wear tolerance and fragrance.

Final practical takeaways

Choose aromatic species (thyme, rosemary, lavender, oregano) to disrupt ant pheromone trails, and pair them with dense-matting groundcovers (ajuga, sedum) for a combined chemical and physical deterrent.
Place aromatic groundcovers as deliberate barrier rows around vulnerable beds, and maintain them so mats remain dense but not thatch-bound.
Reduce the food incentive by controlling aphids and other honeydew-producing pests. Ants will persist where food is guaranteed.
Use caution with invasive or toxic repellant plants; containment or alternative species may be preferable in family gardens.
Combine plant-based deterrents with simple cultural measures: gravel edging, proper mulching, pruning, and encouraging predators. This integrated approach gives persistent and natural control of black garden ants without broad-spectrum insecticides.

Implementing the right groundcover strategy will not eliminate every ant, but it can greatly reduce their numbers and the problems they cause, while improving soil protection, biodiversity, and the look of your garden. Choose plants appropriate to your climate, site, and household, and maintain them with regular pruning and pest monitoring to keep ants at bay.