Saponaria

( sap - on - NAY - ree - uh )

At-A-Glance Information

This genus includes flowering perennial plants that need full sun and moderate to regular water to perform well. They are native to Europe and Asia and grow vigorously, especially in favorable conditions. Soapworts are considered very easy to cultivate in garden settings; some species can even be weedy and a bit invasive, so check with local authorities before planting. Use Saponaria in mixed beds and borders, rock gardens, as small-space groundcover plants, or simply as spiller plants in containers. They are commonly planted in prairie, cottage, informal, and meadow landscapes. Take care when planting these in the landscape, as all plant parts (especially the seeds) are toxic to humans and pets, especially fish.

Saponaria Species and Varietals

The genus Saponaria includes between 30 and 40 distinct species and is a member of the plant family Caryophyllaceae. Saponaria grows well in zones 1-11 and 14-24, though this varies somewhat depending on the species. For more information, see the descriptions below. To find your zone, click here: Zone Map.

Saponaria x lempergii (Giant Flowered Soapwort)
This species grows to 1 foot tall and a foot and a half wide, and has pink flowers with rose calyxes. Variety 'Max Frei' (pictured) blooms profusely with pink flowers in late summer and fall.

Saponaria ocymoides (Silene ocymoides) (Rock Soapwort, Tumbling Ted, Basil Soap-Wort)
This species has a more trailing habit, reaching a foot tall and three feet across. Flowers bloom in springtime and are pink, forming loose bunches that make it look similar to Phlox. This plant is wonderful as a trailing plant over walls and in hanging baskets. This species is native to south-western and southern central Europe.

Saponaria officinalis (Soapwort, Bouncing Bet, Crow Soap, Wild Sweet William, Soapweed, Goodbye Summer)
This species reaches 2 feet tall and spreads by underground runners. Leaves are dark green and flowers form in loose clusters in summertime. Blooms come in red, pink or white. When roots are crushed in water, the plant produces a soap-like lather. It has naturalized itself along railways and roadsides in the West. Varieties include 'Rosea Plena' (with double flowers in light pink) and 'Rubra Plena' (with crimson blooms that fade with maturity).

Saponaria pumila (Dwarf Soapwort)
This species grows well in zones 2-7 and 14-17. Leaves are bright green and flowers are purple-pink and bloom one per stem in springtime around the base of the plant, which forms a mat 2 feet tall and a foot wide. These plants are native to the eastern Alps in Austria and Italy, and the southern parts of the Eastern Carpathians in Romania.

Caring for Saponaria

Saponaria, or Soapwort, should be planted in full sun; ideally, these flowers like to get between 6 and 8 hours of direct sun each day for best performance and flowering. Ensure that soil is well-draining, lean in nutrients, and has a pH of between 6.0 and 8.0 (slightly acidic to slightly alkaline). They thrive in rocky, sandy soils and actually grow better in soils that are on the leaner side; if grown in too-rich soil, they will become floppy. Growing them in lean soil also discourages their aggressive re-seeding tendency. If local soils do not drain well, make sure to amend the planting area with plenty of sand or perlite before installing. Saponaria does not need to be mulched. Water new plantings regularly as they establish a strong root system in their new home. After Soapwort is established, it is considered to be a drought-tolerant plant, able to get by on rainwater alone for most of the year with supplemental waterings in extended periods of drought. Saponaria does not need to be fertilized. Deadhead spent flowers during the growing season to encourage rebloom and clean up the look of the plant. Prune plants back after they stop blooming in autumn. Soapwort can be divided every few years to ensure ongoing health of plants; for instructions on how to successfully divide Saponaria flowers, see the Propagation section below.

Harvesting Saponaria Flowers
Soapwort flowers are used in cut flower arrangements to add an airy but full look. It is one of the easiest, fastest-growing cut flowers to cultivate, and has a vase life of between 7 and 10 days. Harvest flowering stems when about a third of the flowers are opened. The best time to harvest is in the morning a day after the plant receives water. Cut stems at the base of the plant, and immediately dip the bottoms in boiling water for between 7 and 10 seconds before dropping them into a bucket of cool water. The best way to ensure that you have a good stock of cut flowers to pull from throughout the growing season, direct seed and succession plant every two weeks in springtime.

Propagation

Saponaria, or Soapwort, can be propagated by division, cutting or seed. To ensure that your propagated plant will have the exact same qualities and characteristics as the parent plant, use the division or cutting method. If you would like to experiment and see what plant you can grow from seed, just keep in mind that it will not necessarily be the same as the parent plant, especially if you are propagating a hybrid cultivar. To propagate your Soapwort, follow the instructions below:

Propagating Saponaria by Seed

Keep in mind that the plant you get from seed will not necessarily mimic all of the characteristics of the parent plant. To propagate by seed, you will need a paper bag, a pot or tray filled with well-draining compost or other organic material, a spray bottle and a fork. If you don't have any potting medium on hand, you can make some. Just mix together equal parts (by volume) moss peat and horticultural-grade sand or grit sand. You will also, after a few weeks, need individual 3-inch pots for each seedling that grows.
Harvest your seeds. The seed heads on plants are pretty easy to spot, they're left behind after flowers have faded. Once they have dried out and begun to split open, you can harvest the seeds inside. Cut them off of the plant, placing them in a paper bag. Harvest as many as you can, and place the paper bag in a dry, cool, dark area. They will continue to split open and release the seeds contained inside. Once they have been released, take them out of the bag and put them in a container so you can work with them.
Get your container prepared. Water your prepared seed tray or pot filled with soil, and ensure that good drainage is occurring. Place your seeds in your prepared pot or seed tray about a quarter inch to a half-inch under the soil surface. Cover them with soil and water with your spray bottle. Place your tray of seeds in a warm area that receives bright, indirect light. A greenhouse is the most ideal climate, but a planting tray inside a window will do as well. Germination usually takes 2-6 weeks from sowing. Once you begin to see seedlings sprout and they are able to be handled, transplant them to their own individual 3-inch pots, filled with the same potting medium as described in Step 1. Loosen the seedlings from the potting medium by digging down with the tines of your fork about an inch and a half, gently working the seedling up until it is out. Then, replant the seedling in its individual pot.
Keep the seedling's potting medium moist, but not wet, by spraying the soil with your spray bottle. Keep your new plant in an area with bright light (though not direct sunlight) and temperatures between 65 and 72 degrees Fahrenheit. Ensure that the soil stays moist, but not wet, until the next spring (after the danger of frost has passed), when you can transplant it to its new home.

Propagating Saponaria by Cutting

Gather your materials. You'll need a clean, sanitized, sharp pair of garden shears, rooting hormone, a pencil, and a 3-inch pot filled with well-draining compost or other organic material. If you don't have any potting medium on hand, you can make some. Just mix together equal parts (by volume) moss peat and horticultural-grade sand or grit sand.
In early summertime, choose the plant that you'd like to propagate. Ensure that this plant has had a good watering the night before, as this will improve the chances your cutting will take root. Cut one or more 3-4 inch portion(s) of the end of a non-blooming branch and strip the leaves off of the lower half. Make a hole in your planting medium by pushing your pencil into the soil. Dip the end of the stem in rooting hormone, and plant it in your pot. Fill in soil around the cutting to support it, but do not pack it down too much.
Moisten with water, and ensure that the pot has good drainage. Your pot should be kept in warm, sunny conditions indoors (and not in direct sunlight). Water whenever your soil is dry under the top layer. After about four to six weeks have passed, your cutting should be rooted. When you notice new growth, you'll know you have roots.
Keep your new plant in an area with bright light (though not direct sunlight) and temperatures between 55 and 70 degrees Fahrenheit. Ensure that the soil stays moist, but not wet, until the next spring, when you can transplant it to its new home. Ensure that the last frost of the year has occurred before doing this, as it can seriously damage your new plant.

Propagating Saponaria by Division
This type of propagation is relatively simple; you will need a clean shovel, mulch, fresh soil (any kind will do, though it does need to be well-draining), compost and pots (only necessary if you will be saving divided plants for transporting elsewhere). Division is best done in very early spring (after the plant has entered dormancy, but before it has begun its new spring growth), and needs to be done every few years regardless of whether you have the goal of propagating the plants for best performance. To propagate by division, follow these steps:

Using a shovel, dig up your existing plant. Start from the outside and work your way in to avoid damaging the root(s). Once you have worked it up out of the ground, lay it out.
Start to tease apart the roots with your gloved fingers. Once the roots are untangled, separate your plant into segments, ensuring that each one has at least one thick root section attached.
Prepare your pot(s) or new planting site(s) with amended, well-draining soil. You can either bring in new soil or simply amend your existing soil with compost to complete this task. Then, plant your divisions and water thoroughly.
Apply a thick layer of mulch over the new planting to protect it from cold weather as it acclimates to its new home. Then, enjoy watching it sprout in the next growing season.

Soapwort seed heads remain after flowers fade.

Soapwort seeds are typically rounded and dark brown to black in color.

Problems and Pests

Saponaria plants are considered to be invasive in many areas of North America, where they have become widely naturalized and are considered to be weeds. Check with your local extension program or other authority before planting.

Saponaria, or Soapwort, plants can be susceptible to developing issues with the following pests and diseases in the landscape: