Slug Proof Garden: Slug Resistant Perennials for a Slug Free Garden

The problem with slugs is that they relish gardens. They appreciate the edibility of fruits, ornamentals, and vegetables. With their voracious appetites, slugs easily partake their way through these favored food sources. Gardeners despair when day breaks upon the unmistakable evidences of slugs' nightly feastings.

Strategies for exiling slugs from gardens encompass chemical as well as natural measures. The concern with chemicals is that they often are toxic and fatal as well to accidental garden visitors, such as pets. Natural measures include surrounding garden plants with dry mulch, such as pine needles which repel slugs with their acidity. Strewing the soil with coffee grounds, copper plates, crushed egg shells, sand, or stone chips all solve the slug problem by desiccating them or gutting their sensitive bellies. Salt also dessicates slugs but is not desirable for a slug invasion as the soil salinity may be increased.

Three additional organic methods which are highly effective and cause no suffering to the slugs involve:

1. Planting, at judicious intervals throughout the garden, red-leaved or red-stemmed and red-ribbed plants, such as Swiss chard (Beta vulgaris subsp. cicla), which shoo slugs from their vicinity, as red-leaved or red-ribbed plants are repugnant to slugs;
2. Removing slugs to the compost pile, where the slugs will live a happy, satisfied life and eventually decompose at life's end along with the rest of the compost bin;
3. Encircling the garden with slug-proof perennials which are known to disinvite these undesirable visitors.

Planting slug-free perennials as barriers effectively excludes pesky slugs from the garden as well as beautifies the garden vista. Although these perennials successfully shun slugs, they form a stunning and often fragrant enclosure around garden valuables. Following are slug-free perennial suggestions for various hardiness zones.

Aconitum carmichaelii, commonly known as monkshood, reaches a height of 7 feet (2 meters) with a spread of 24 to 36 inches (60 to 90 centimeters).

White to mauve helmet-shaped flowers grow densely in spikes against dark green, toothed, leathery leaves which curl to reveal pale undersides.

The Royal Horticultural Society has bestowed its prestigious Award of Garden Merit (AGM) upon two monkshood cultivars:

• Aconitum carmichaelii (Arendsii Group) 'Arendsii' in 2002, and
• Aconitum carmichaelii (Wilsonii Group) 'Kelmscott' in 1993.

Caution should be exercised, as:

• contact with Aconitum foliage may cause skin irritations;
• ingestion of any part of Aconitum plant may provoke high toxicity.

Geranium macrorrhizum, commonly known as bigroot geranium, reaches  a height of 20 inches (50 centimeters), with a generous spread of 40 inches (100 centimeters).

Dense clusterings of flowerheads open as gorgeous pink to purple-red flowers.

Geranium macrorrhizum combines the double threat of dissuading both deer and slug inquirers from entering the garden.

Two cultivars of bigroot geranium have been recognized with the Royal Horticultural Society's Award of Garden Merit (AGM):

• Geranium macrorrhizum 'Ingwersen's Variety' in 1993, and
• Geranium macrorrhizum 'White-Ness' in 2006.

Dicentra eximia, commonly known as fringed bleeding-heart, staggerweed, turkey corn or wild bleeding-heart, reaches a height of 12 to 26 inches (30 to 65 centimeters) with a spread of 20 to 40 inches (50 to 100 centimeters).

From mid-summer to autumn, flowers open in sprays of pink or white heartshaped flowers which contrast strikingly with the finely divided, blue-green leaves.

Caution should be exercised, as:

• contact with Dicentra foliage may activate skin allergies;
• ingestion of any part of Dicentra plants may provoke mild stomach upsets.

Hosta x tardiana 'Halcyon,' commonly known as Halcyon hosta, reaches a height of 16 inches (40 centimeters) with a spread of 16 to 20 inches (40 to 50 centimeters).

Lavender-grey flowers open in bell shapes above heart-shaped blue-grey leaves.

Hostas are not accepted or rejected categorically by slugs. Tardiana hostas number among Hosta species which are undesirable to slugs. Other slug-resistant hostas include:

• Hosta rupifraga
• H. sieboldiana
• H. tokudama.

Hostas which are prone to slug attention include:

• H. crispula
• H. hypoleuca
• H. kikutii
• H. pycnophylla
• H. ventricosa.

 'Halcyon' received the Royal Horticultural Society's Award of Garden Merit (AGM) in 1993.

Allium 'Globemaster,' commonly known as ornamental onion, reaches a height of 24 to 36 inches (60 to 90 centimeters), with a spread of 6 to 12 inches (15 to 30 centimeters).

Flowers open as deep violet in 6- to 8-inch (15- to 20-centimeter) wide flowerheads, perched like globes atop grey-green stems.

The Royal Horticultural Society bestowed upon Allium 'Globemaster' its prestigious Award of Garden Merit in 1995.

Helleborus x nigercors, commonly known as hellebore snow love, is equiproportional, with both a height and a spread of 24 inches (60 centimeters).

Helleborus x nigercors is a cross of Hellebrous argutifolius, commonly known as Corsican hellebore, with its large, 2-inch (5 centimeter) wide, green flowers, and Helleborus niger, commonly known as Christmas rose, with large, up to 4-inch (10-centimeter) wide, pale white flowers flushed with light green or pink.

Helleborus x nigercors flowers open as saucer shapes of white or white tinted with pink or blue green and bloom from winter to spring.

Helleborus x nigercors also is dissatisfactory to white-tailed deer, so a garden noticed by deer and slugs will be disenchanted quickly of these visitors with the addition of this plant.

Caution should be exercised, as:

• contact with Helleborus sap may cause skin irritations;
• ingestion of any part of Helleborus plants may provoke severe discomfort.

For gardens overrun by slugs, there are many options.

• Enclosing gardens with slug-proof perennials provides an effective, natural solution to the problem.

Perceiving the presence of disagreeable plants, slugs trespass no further and either find alternatives, such as nearby dandelion fields, or die searching.

• A tangential remedy is to relocate slugs to the compost pile, where their contributions to decomposition excel.

In turn, gardeners are relieved easily of pests and derive further enjoyment from the increased visual beauty ensuing from the spectrum of slug-proof perennials.

My special thanks to:

• Talented artists and photographers/concerned organizations who make their fine images available on the Internet;

• Virginia Polytechnic Institute and State University for superior on-campus and on-line resources.

"Allium 'Globemaster' AGM." Royal Horticultural Society > Plants > Plant Selector. 2011. The Royal Horticultural Society. Web. www.rhs.org.uk

• Available at: http://apps.rhs.org.uk/plantselector/plant?plantid=97 

Brickell, Christopher, and Judith D. Zuk, eds. The American Horticultural Society A-Z Encyclopedia of Garden Plants. New York: DK Publishing, 1996.

"Dealing with Slugs in the Hosta Garden." Perfect Perennials. Perfect Perennials Nursery. Web. perfectperennials.tripod.com

• Available at: http://perfectperennials.tripod.com/id7.html

Flora: A Gardener’s Encyclopedia. Volumes I-II. Portland OR: Timber Press, 2003.

Lancaster, Roy. Perfect Plant Perfect Place: The Surest Way to Select the Right Outdoor and Indoor Plants. London-New York-Sydney-Moscow: Dorling Kindersley, 2002.

"RHS AGM Listing May 2013 (Ornamentals)." Royal Horticultural Society > Plant Awards > List of plants with the AGM. May 2013. The Royal Horticultural Society. Web. www.rhs.org.uk

• Available at: http://www.rhs.org.uk/Plants/Plant-trials-and-awards/Plant-awards/AGM-plants

"Slug Resistant Plants." The Gardeners Guild > Gardening Tips. The Gardeners Guild (TGG). Web. www.thegardenersguild.co.uk

• Available at: http://www.thegardenersguild.co.uk/Slug_resistant_plants.html

Symondson, William O.C. “Slug Control.” Cardiff School of Bioscences > StaffInfo > Slugs. October 1996. Cardiff University. Web. www.cardiff.ac.uk

• Available at: http://www.cardiff.ac.uk/biosi/staffinfo/wocs2.html