Ground Cover

Sweet Woodruff: Shade-Loving Perennial Groundcover


Sweet woodruff

Finding a ground cover that can survive underneath shady trees can be a challenge for many gardeners. Many plants can’t survive without sunlight, or they at least won’t grow prolifically like you want them to. Sweet woodruff may be able to solve your problems! This aggressive plant thrives in full shade and spreads quickly, making it an efficient and durable ground cover. It can even grow underneath black walnut trees where many other species struggle.

Sweet woodruff is appropriately named since it has a pleasant scent close to freshly mown hay. You can save some leaves and dry them to make a potent potpourri if you enjoy the scent enough. Its pretty white flowers will attract pollinators and make your yard look beautiful.

It’s an attractive ground cover that will happily grow in areas a variety of plants won’t, but do note that it grows so quickly that it’s considered invasive in many areas. If you let it grow in an open area, you’ll need to prune it regularly to stop it from spreading. But it won’t last long if it escapes the shade of a tree, so that may make it easier to handle.

Let’s take a look at how to grow this durable plant so you can know if it’ll be a good fit in your garden.

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Quick Care Guide

Sweet woodruff
Sweet woodruff is a shade-loving, low-growing ground cover. Source: Leo Reynolds
Common NameSweet woodruff, sweet scented bedstraw, wild baby’s breath
Scientific NameGalium odoratum
FamilyRubiaceae
Height & SpreadHeight: 6-12 inchesSpread: 9-18 inches
LightPartial shade, full shade
SoilAverage, well-draining
WaterKeep soil moist
Pests & DiseasesLeaf spot, powdery mildew, slugs, rust

All About Sweet Woodruff

Galium odoratum (common name: sweet woodruff) is a plant commonly used as a ground cover in the desolate parts of the yard where some plants can’t grow. Growing it underneath trees is common because the tree roots deter competition from growing, and the branches and leaves can hog all the sunlight. Sweet woodruff is stronger than it looks and will assert dominance by sending out creeping roots to establish itself.

Sweet woodruff doesn’t look like a fighter. Its six to nine lance-shaped leaves come out from the stems to create a circular or star shape, and it grows many star-shaped flowers, giving it a dainty appearance. The leaves can be light or dark green leaves, and the white flowers tend to look like white stepping stones from a distance.

The growth habits of this plant make it a force to be reckoned with. When it’s given the right growing conditions, it will send out creeping roots that will grow more stems and leaves, allowing the plant to spread out like the mat-forming perennial that it is. The stems can easily break off from the roots, and if the roots are left intact, they will eventually grow more stems. This is annoying if you’re trying to get rid of it, but this also means you can mow over it when it gets too tall, and it’ll come back.

The plant can grow up to 1 foot (30 centimeters) in height, so mowing may be required if you live in an area with lawn height limitations. A single plant can spread out to 1.5 feet (45 centimeters), so even one plant will be enough to cover a planter.

The plant isn’t edible, but its freshly mown hay scent is fragrant enough to make potpourri. It’s also used to make Maiwein, or May wine, a white wine flavored with sweet woodruff, orange, and pineapple leaves. The plant is native to northern Africa (particularly North Africa) and northern and central Europe and has been utilized for medicinal uses. Its dried leaves were also used in bygone years to stuff mattresses or to scent linen, giving it the common name of sweet-scented bedstraw.

Planting Sweet Woodruff

Planting sweet woodruff is fairly easy, and once planted, it’ll stick around in your garden for a while. You can easily find seed packets online, but your local garden center may have plant starts in early spring.

The best time to plant seeds in the ground is in late winter, about ten weeks before the last frost date. They benefit from cold exposure, so freezing temperatures won’t hurt the seed. Sprinkle them over the ground and lightly cover them with soil and water them. Water them at least once a day and make sure the ground stays moist but not wet. Avoid planting them in an area where water puddles since the plants can’t tolerate standing water. 

You can wait a little longer if you’re starting seeds indoors and aim for early spring sowing instead. The seeds will need to be refrigerated for two weeks, but they should start germinating quickly if you keep them at 50°F (10°C). You can transplant seedlings outside after they have several sets of leaves and there’s no longer any danger of frost.

Since sweet woodruff likes lots of shade and spreads rapidly, the best place to plant it outdoors would be underneath a tree. Some trees, like the black walnut tree, are allelopathic, meaning that they create chemicals like juglone that weaken or kill a variety of plants. Galium odoratum isn’t affected by juglone, making it the perfect choice for areas that are difficult to keep planted! Sweet woodruff will also work well in a flower bed or planter that gets shade for most of the day if you don’t want it to spread or become invasive. 

Care

Sweet woodruff is only picky about sunlight and water, so they’re pretty easy to care for as long as you remember to limit their sun and give them their water. If you live in an area where it frequently rains, growing them won’t require much effort.

Sun and Temperature

Sweet woodruff grows well in USDA zone 4-9. You may be able to get them to grow in higher or lower zones, but it will require extra care, and you’ll probably need to stick to containers so you can move them to shade or indoors as needed.

This plant prefers partial to full shade, which means little to no sun. Dappled sunlight is best, and that’s when rays of light poke through the tree canopy throughout the day. It may be able to grow on the north or east-facing side of your house if there are trees or a fence on the east side that blocks most of the morning sun, and the house blocks most of the afternoon sun.

The hotter your climate is, the more shade your sweet woodruff will need. It can’t tolerate heat and may go dormant in the late spring or throughout the summer if it gets too much sun and not enough water. 

Water and Humidity

If it often rains in your climate, you won’t have to think about this part as much! But for people who live in areas that are prone to drought and high temperatures, you’ll need to water these plants almost every day, depending on how dry the ground is. If you live in the southwest United States, don’t expect this plant to do well since it can’t tolerate desert conditions.

Aim for always moist soil but not sopping wet. Water should be able to drain away easily and not create puddles. Watering every day might not be necessary. The best way to gauge if your plants are thirsty is if the top inch or so of soil is dry. If you want to plant sweet woodruff in a dry shade area that receives almost no sun, it will be able to tolerate dry shade conditions better than it would if it received sun.

The best way to water is to do it early in the morning so the leaves will have all day to dry out. Wet leaves will increase the chances of diseases and pests. Soaker hoses are the best way to prevent wet leaves, but it won’t be the end of the world if you use a sprayer nozzle to water them.

Soil

Sweet woodruff isn’t picky about soil. It prefers slightly acidic soil but can tolerate a wide range of pH levels between 4.3-8.3. It can tolerate somewhat nutrient-deficient soil, but adding a generous amount of compost or decaying leaves before you plant it will give it a better start.

The most important aspect of soil that will make or break your ground cover is its ability to drain. Sweet woodruff needs well-drained soils that won’t hold excess water. While it should be well-drained soil, it should still be consistently moist and damp to the touch, but never oversaturated. Sweet woodruff can’t tolerate wet feet, and the full shade conditions it loves make it harder for water to evaporate.

Fertilizing

Sweet woodruff doesn’t require fertilizing unless your soil is completely out of nutrients. If it seems like your plants need a nutrient boost, add a fresh layer of compost once or twice a year. Even a simple layer of decaying leaves will help.

Pruning

Pruning isn’t necessary if you’re allowing it to grow freely, but you may want to prune it if you want to stop it from spreading or if you don’t like how thick it’s become. 

You need to break off the roots to stop them from spreading. To do this, drive a garden spade or shovel deep into the ground to break the roots and remove them. You don’t need to worry about removing stems and leaves—that’s free compost!

Sweet woodruff can grow pretty tall for a yard. If you’re not concerned about spreading but want to make it shorter, you can mow over it with a rotary mower like you would for grass. It’s best to use a high setting, so you don’t accidentally cut it too short.

Propagation

Sweet woodruff can multiply by sending out new roots or by self-seeding. If you want to start them somewhere else, you can remove a clump of the plant, roots and all, and plant it in another shady area. 

Troubleshooting

Sweet woodruff is mostly easy to grow and has very few insect and disease problems. Here are a few of the issues you might come across and what to do about them.

Growing Problems

The biggest issue with sweet woodruff is that it can become invasive if you care for it properly and let it spread as it pleases. Full shade and enough water will keep it growing. You can contain it in a planter or flower bed or prune it once or twice a year to prevent it from spreading. As annoying as it may be, prolific growing means you’re doing it right!

As your plant ages, you may notice leggy growth. This is simply part of the aging process. Remove the leggy stems and leave the roots intact, and the plant will renew itself in no time.

Pests

Very few pests bother sweet woodruff, which is why so many gardeners love it! The only pest that may become a problem is slugs. They’re 1-2 inches long and can be brown, black, yellow, grey, or white. If your plants are in moist acidic soil, you’ll likely see more slugs since they love the acidity and moisture, too.

Slugs devour stems and leaves and are a serious threat to young seedlings. Protect your seedlings by covering them with row covers and removing slugs by hand as soon as you see them. Start your seedlings indoors if you can, and don’t move them outside until they’re sturdy.

Diatomaceous earth is a natural and effective way to get rid of them. Sprinkle it on the ground around your plants and it will injure the slugs as they move on it and eventually kill them. The cool part is that it DE won’t hurt you or your plants, only the slugs and any other insect that touches it. If you do not have DE right at hand, an organic slug and snail bait is also very effective.

Diseases

Sweet woodruff isn’t prone to disease, and there are only a few you need to look out for. Diseases often occur when the plants don’t have enough air circulation, and the conditions are too wet. Pruning and decreasing how much water you give them is usually enough to reverse the problems.

The most common disease is powdery mildew. It’ll look white and chalky and can be found on the leaves. There isn’t a cure, but removing the affected part of the plants will slow its spread. You can use neem oil or copper fungicide as a preventative measure in most regions, but it’s not guaranteed to prevent it in humid, warm locations.

Leaf spot will cause yellowish-brown discolored areas with brown spots. Rust is a fungus that will look like yellow or rust-colored spots. Treatment of these involves removing infected material and applying a copper fungicide to reduce the likelihood of further spread.

Frequently Asked Questions

Q: How invasive is sweet woodruff?

A: Sweet woodruff spreads quickly and can take over an area if the conditions are right. It can grow under allelopathic trees where other plants can’t, and it’ll happily fill up the entire garden and then some if it has the opportunity.

Q: Will sweet woodruff choke out other plants?

A: It can choke out other plants since it grows quickly and forms a mat. Competitive weeds might survive, but your other flowers probably won’t.

Q: How long does it take for sweet woodruff to spread?

A: Under the right conditions, it can reach its full spread of 18 inches in just one year.

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