Sweet Woodruff: So Much More Than a Groundcover!

Sweet woodruff is attractive, fast-growing and so easy to grow … and that’s only the beginning! Photo: vanberkumnurserycom

One of my favorite ground covers is sweet woodruff. I just love the way it forms a nice uniform carpet even in the most shaded areas and stays green until the snow hits. And that sprinkling of tiny white flowers is just sublime.

However, its use as an ornamental ground cover remains relatively recent. Previous generations knew it better as a culinary and medicinal herb. Even in my local garden center, it’s still sold in the herb section … much, I’m sure, to the surprise of many gardeners who would have no idea of how to use it for herbal purposes.

Origin: Sweet woodruff is a small herbaceous perennial found in shady or humid environments throughout temperate Eurasia from Spain and Ireland to Japan, and also Algeria. It has sometimes escaped from culture in the United States and Canada, although only very locally.

The botanical name Galium odoratum comes from the Greek gala (milk), as certain species of bedstraw were once used to curdle milk, while odoratum, from Latin, obviously refers its attractive yet rather unusual scent: the leaves, stems and rhizomes smell of freshly mown hay. The flowers do as well, but to a lesser degree. That’s because they’re rich in coumarin, an aromatic organic chemical compound.

Despite the “sweet” in its name, the plant is not strikingly fragrant … well, at least not in the garden. It’s when it has been dried that it best emits its pleasant fragance.

As for the origin of its numerous common names, woodruff refers to the plant’s habit of growing in woodlands as well as its whorls of leaves that look rather like ruffs (pleated collars). As for bedstraw, the dried leaves (straw) were once used to stuff pillows and mattresses (beds) where they offered not often comfort and a pleasant scent, but were believed to repel lice and bedbugs.

Description: Sweet woodruff is actually a very simple little plant. Each consists of an erect stem, several tiers of dark green, narrow leaves placed in a whorl (attached to the stem like the spokes of a wheel) and, in late spring or early summer, depending on the local climate, a cluster of small white 4-petaled flowers.

At least that’s what you see above the ground. Below, it reaches out to a whole colony of other plants through a series of thin rhizomes running horizontally just below the surface and it’s these rhizomes that produce this dense groundcover effect that has come to be its main ornamental feature.

The plant makes a very dense and very even groundcover … and a very attractive one, too. In fact, you really have to grow this plant en masse to appreciate its appearance: even without flowers, a carpet of sweet woodruffs is absolutely charming.

The foliage is semi-evergreen: in mild climates, it may persist all winter. In cold climates, it remains fully green until a seriously hard frost or the first snowfall, then dies back. It greens up quite quickly in the spring.

Cultivation: Prefer a semi-shaded to shaded location, with preferably rich and fairly moist soil. That said, it seems perfectly adapted to the dry shade caused by shallow tree roots. It will, though, object to severe drought, especially when planted in full sun. Under arid conditions, it tends to go summer dormant and turn yellow, so is not a good choice. It can, though, be grown in full sun in areas with relatively cool summers or spots where the soil stays evenly moist. 

This plant is much hardier than it’s often given credit for being. Many otherwise serious gardening sites suggest USDA hardiness zones 5 to 8, yet it seems perfectly fine in zone 2 (AgCan Zone 3). In fact, it seems to need a cool to cold winter to thrive and won’t be happy in outside of temperate regions.

Do be forewarned that this plant really is a groundcover, with the accent on the word cover: given a chance, it will spread quite fast. That’s interesting when you first plant it, as it fills in at a rapid rate, but it may not stop where you had planned. It can easily push out from the original planting at a rate of up to 18 inches (45 cm) a year, at least where conditions are to its liking. 

Make sure you control it with a barrier of some sort to keep it under control. Even simple lawn edging will suffice: just make sure you allowing the top of the barrier to protrude about 1 inch (2.5 cm) above the soil so it can’t creep over top.

If you ever plant it without a barrier and it “jumps the fence”, you’ll discover it’s actually fairly easy to control. It’s simple to pull out or hoe into submission and will be killed outright if you cut it to the ground in early summer. Intolerant of low mowing, it rarely invades lawns. 

However, it also doesn’t tolerate foot traffic. Like, don’t walk on it at all if you can help doing so. You can plant it between stepping stones as long as you keep to the pavers, but you certainly can’t walk on it regularly. 

Other than watering in times of drought, this plant needs no maintenance, not even fertilizing.

Harvesting: For culinary, aromatic or medicinal purposes, harvest sweet woodruff during or just before flowering, when its somewhat bitter flavor and its aroma are at their most intense. Don’t cut whole swathes to the ground, though, as that will impede the groundcover’s ability to photosynthesize and recover, leaving bare patches. Instead, pick only of one stem out of 4 or 5. That will be hardly noticeable and besides, neighboring plants will soon fill in the gap with new plants from rhizomes.

Sweet woodruff is used both fresh and dried, but tends to turn black under humid conditions. So, dry it rapidly. To do so, tie stems it into small bunches and hang them upside down indoors in a dark, cool, dry spot with good air circulation so they can dry without delay.

Propagation: Usually done by division in spring or fall, or by stem cuttings after flowering. Also, by seed which germinates without any special treatment. Interestingly, the seeds bear tiny hooks and are spread by sticking to the fur of animals.

Horticultural Uses: Sweet woodruff is an excellent groundcover for forest and shaded environments, growing especially well in the dry shade at the base of deciduous trees. You may, however, find it too invasive for very orderly flower beds.

Medicinal Uses: The pleasant “freshly cut hay” scent of sweet woodruff comes, as mentioned above, from coumarin which has several medicinal properties, used among others in antispasmodic, cardiac, diuretic and sedative treatments. The plant is also slightly toxic (as are most medicinal plants) and should only be used at low doses. Avoid use entirely during pregnancy and lactation. 

Culinary uses: Sweet woodruff can be used fresh or dried to flavor cakes, cookies, jellies and also drinks, both alcoholic and not. Among others, it’s used to produce Maitrank, a popular aperitif in Germany and parts of Belgium and Luxembourg. The name means “May drink” for the month it which it’s produced and is prepared by macerating the flowering stems in white wine.

Other Uses: As mentioned above, sweet woodruff was once used to stuff pillows and mattresses and was also a strewing herb, that is, it was spread over dirt floors to hide unpleasant odors. Today, it is still used to aromatize potpourris and sachets and as a moth deterrent.

Plant Groupings: Sweet woodruff is a superb ground cover for use with early spring bulbs, such as Siberian squills (Scilla siberica) and crocuses (Crocus spp.), as it begins to grow back just as their flowering ends, hiding their yellowing foliage from sight. It also works well as a living mulch around medium to tall perennials and shrubs, surrounding them with an attractive green carpet, but can shade out lower-growing varieties. It also offers a charming green carpet effect to park woodlands and is unharmed by moderate accumulations of fall leaves. In fact, they tend to work their way to the base of the plants and disappear from sight. 

?Helpful Hint: Sweet woodruff seems to grow well under walnut trees (Juglans spp.), known to be hostile to many other plants.

Problems: No serious insect or disease problems. Its fragrance, which we find pleasant, is in fact a natural insect repellant. Also, herbivorous mammals, such as deer, hares and rabbits, don’t seem to bother it either. Chicken, though, apparently love it and need to be kept out of the sweet woodruff patch.

Other Galiums: The cosmopolitan genus Galium (most species are called bedstraws) includes more than 700 different species … but unfortunately many are weeds!

Where to Find Sweet Woodruff? In season, almost all garden centers carry it, at least in areas where it grows well. Many mail order nurseries that specialize in perennials, groundcovers or herb also offer it. 

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Sweet woodruff: yet another living tool for low maintenance landscaping!