Costmary: The Fragrant Herb Your Garden Might Be Missing
If you’ve ever wondered what gave colonial American gardens their distinctive sweet, minty fragrance, you might want to meet costmary (Tanacetum balsamita). This aromatic perennial herb has been perfuming gardens and flavoring dishes for centuries, though it’s become something of a forgotten treasure in modern landscaping.
What Exactly is Costmary?
Costmary is a perennial forb – basically a non-woody herbaceous plant that comes back year after year. Its silvery-green, oval leaves release a delightful balsamic scent when brushed against or crushed, earning it the nickname bible leaf because people used to place the fragrant leaves between pages of their prayer books. In late summer, it produces clusters of small, white button-like flowers that add a subtle charm to the garden.
Where Does Costmary Come From?
Originally hailing from western and central Asia, including the Mediterranean region, costmary isn’t native to North America. However, it has naturalized across much of the continent and can now be found growing in numerous states and provinces, including California, Colorado, Connecticut, Illinois, Maine, Massachusetts, Michigan, New York, Ohio, Oregon, Pennsylvania, Washington, Wisconsin, and many others, as well as in Canadian provinces like Ontario, Quebec, and Nova Scotia.
Should You Plant Costmary in Your Garden?
The answer depends on what you’re looking for in a garden plant. Here are some reasons you might want to give costmary a try:
- Historical interest: Perfect for heritage or colonial-style gardens
- Fragrance: The leaves provide wonderful aromatic interest
- Low maintenance: Once established, it’s quite drought tolerant
- Pollinator support: The flowers attract bees and beneficial insects
- Culinary uses: Leaves can be used sparingly to flavor soups and stews
However, there are some considerations to keep in mind. Costmary can be quite the spreader, sending out underground rhizomes that can quickly colonize an area if left unchecked. This vigorous growth habit means you’ll need to stay on top of managing its spread.
Growing Costmary Successfully
If you decide to welcome costmary into your garden, here’s what you need to know:
Climate Requirements: Costmary thrives in USDA hardiness zones 4-8, making it suitable for most temperate climates.
Light and Soil: This adaptable herb prefers full sun but tolerates partial shade. It’s not particularly fussy about soil, doing well in average, well-drained conditions. In fact, it can handle poor soils and drought once established – though it will spread more aggressively in rich, moist conditions.
Planting and Care:
- Plant in spring after the last frost
- Space plants about 2-3 feet apart (trust us, they’ll fill in!)
- Water regularly the first year, then reduce as the plant establishes
- Cut back flowers after blooming to prevent self-seeding
- Divide clumps every 3-4 years to manage spread and rejuvenate plants
- Consider planting in containers or using root barriers to contain growth
Design Ideas and Garden Placement
Costmary works beautifully in herb gardens, cottage-style borders, or historical garden recreations. Its silvery foliage provides nice contrast against darker green plants, and its spreading habit makes it useful as an informal groundcover in larger spaces. Just remember to give it room to roam or be prepared to keep it in check.
Native Alternatives to Consider
While costmary isn’t invasive, gardeners interested in supporting local ecosystems might consider these native alternatives that offer similar benefits:
- Wild bergamot (Monarda fistulosa): Aromatic leaves and excellent pollinator flowers
- Yarrow (Achillea millefolium): Feathery foliage and long-lasting flowers
- American pennyroyal (Hedeoma pulegioides): Small but intensely fragrant native mint
The Bottom Line
Costmary offers gardeners a chance to grow a piece of horticultural history while enjoying its unique fragrance and subtle beauty. While it requires some management to prevent it from taking over, it’s not considered problematic in most areas. Whether you’re creating a historical garden, need a fragrant addition to your herb collection, or simply want to try something different, costmary might just be the aromatic adventure your garden needs.
Just remember: with great fragrance comes great responsibility – keep those spreading roots in check!
