How to Grow Soapwort

close up view of the flowers on a soapwort (Saponaria officinalis) plant

Nigel Hicks / Dorling Kindersley / Getty Images

In This Article

Soapwort is a multipurpose perennial herb that has a place in any herb garden. As its name suggests, soapwort has long been used to make detergent and soap, thanks to the saponins in its roots and leaves that create bubbles. Beyond the practical, the plant also has ornamental value.

Native to Europe and Asia, soapwort grows erect with green, leafy stems that are devoid of side branches. It readily flowers throughout the summer months, with blooms forming in clusters that give off a sweet, floral scent somewhat reminiscent of cloves.

Soapwort is a very fast-growing plant that readily self-seeds. It will grow successfully no matter when it's planted, though it's traditionally thought best to start it in early spring after the risk of frost has passed. Soapwort is so easy to establish that it is actually regarded as invasive in many regions, so take care to supervise its spread if you choose to plant it in your garden.

Botanical Name Saponaria officinalis
Common Name Soapwort, common soapwort, bouncing-bet
Plant Type Herbaceous perennial
Mature Size 1–3 ft. tall, 1–2 ft. wide
Sun Exposure Full sun, partial shade
Soil Type Dry to medium moisture, well-drained
Soil pH Neutral to acidic
Bloom Time Summer, early fall
Flower Color Pink, white
Hardiness Zones 3–9 (USDA)
Native Area Europe, Asia
Toxicity Toxic to humans, dogs, and cats

Soapwort Care

Soapwort is a vigorously growing plant that requires little maintenance. In fact, the most effort you'll put into the plant may be stopping it from spreading all throughout your garden. The herb isn't very fussy about where it's planted, though it prefers a sunny spot with well-draining soil. Soapwort is suitable for use as a ground cover, edging, atop walls, on a living roof, and more. It's also a good choice for gardeners seeking to attract pollinators. Additionally, it experiences few issues with pests and disease.

Soapwort has seen various applications throughout history. The Romans were said to have used the herb as a water softener. Farmers would make soap out of it to bathe sheep before shearing and colonists to the United States brought the plant with them from Europe as a soap substitute.

When roughly chopped and boiled in some water, soapwort creates a cleanser that can effectively remove oils, but is so mild that museums sometimes even use it to wash delicate textiles. At home, you can use it to launder fragile fabrics, such as lace or linen. Soapwort also is gentle on sensitive or irritated skin and it's not uncommon to boil its roots to make a wash for itchy skin, acne, and psoriasis. Boiling the leaves, stems, and roots of the plant can also create a sudsy hair-washing solution.

Light

To grow a dense plant with plenty of blooms, plant your soapwort in full sun. It also can tolerate a bit of shade (especially in warmer climates), though the plant might not be as lush. Ultimately, six to eight hours of direct sunlight will result in the fullest and most plentiful blooms.

Soil

Soapwort is easy to grow in most soil varieties, as long as the mixture is well-draining. However, when planted in moist, rich soil, soapwort might grow uncontrollably and take on a disheveled and floppy appearance. Soil that is slightly rockier can help to temper its growth. 

Water

Like most herbs, soapwort prefers consistent moisture but can tolerate a few days of drought once established. When watering the plant, make sure to soak the soil well, then wait for it to dry to the touch (but not completely through) before watering again.

Temperature and Humidity

Soapwort is a hardy plant that thrives in the full range of conditions found in its growth zones. It prefers a minimum of 130 frost-free days per year, though it can survive winter temperatures well below freezing. In colder climates, a layer of mulch can help protect the plant over the winter.

Fertilizer

Once established, soapwort plants can grow for years with little assistance. If you have poor soil, consider fertilizing your plant once per year in the spring with an all-purpose fertilizer. Feed it lightly—too many nutrients can actually damage the plant and hinder its growth.

Is Soapwort Toxic?

Although soapwort has some usage in the culinary world—including creating foam on beer and brewing tea for throat issues—it's best not to eat it. The herb is toxic in high doses and can cause vomiting, diarrhea, and other mild issues in humans, and potentially more severe issues in animals.

Most animals will instinctually stay away from the plant, but it's a good idea to be mindful of where you plant it anyways should you have curious pets or children around. The saponins in soapwort also are harmful to fish, so don't plant it next to any bodies of water where aquatic life resides. If you suspect poisoning or notice any of the symptoms below, contact a poison control center promptly.

Symptoms of Poisoning in Humans

  • Nausea
  • Vomiting
  • Diarrhea

Symptoms of Poisoning in Animals

  • Nausea
  • Vomiting
  • Diarrhea
  • Cramping
  • Dark urine
  • Muscle spasms
  • Lethargy
  • Weight loss
  • Drooling
  • Head shaking
  • Seizures
  • Skin irritation

Pruning Soapwort

Deadhead the flowers during their blooming period to promote continued flowering. Once the plant is finished blooming in the fall, cut it back by about half (especially if it experienced robust summertime growth). This helps to keep soapwort neat and healthy and it limits invasive spreading.

Propagating Soapwort

Soapwort spreads with creeping underground rhizomes and easily reseeds itself. If you wish to plant it in different locations, it’s easy to take divisions from an established soapwort plant with the roots attached. This should be done in the spring or fall, though divisions can be successful at any point during the growing season as long as they're kept moist. Soapwort is typically not ideal for planting in pots due to its growth habit.