Aethionema

( eeth - ee - oh - NEE - muh )

At-A-Glance Information

Commonly referred to as Stonecress, this herbaceous perennial (sometimes annual) shrublet needs full sun and little to moderate amounts of water. Their spring to early summer flowers and foliage are both fragrant. Native to the Mediterranean and Asia Minor, these small shrubby flowers are attractive in bloom (in spring and summer) as well as in their dormant stages. They form woody bases that are herbaceous at the tips. Stonecresses are great plants in cold climates and in rock gardens, and their blooms can be extended even longer if the plant is deadheaded regularly. Plant stonecress in mixed beds, containers, or in cracks in rock walls or steps.

Aethionema Species and Varietals

Aethionema is a genus of approximately 60 species included in the family Brassicaceae, and derives its name from an Ancient Greek word meaning 'to light up, kindle'. The common name 'Stonecress' refers to its creeping habit and preference for stony, rocky planting sites. They are relatives of plants like Mustard and Cabbage. Aethionema grows best in USDA growing zones 4-8 or Sunset zones 1-9 and 14-21. For more growing information, see the species descriptions below. To find your zone, click here: Zone Map.

Aethionema armenum (Rock Cress, Persian Candytuft, Armenian Stonecress)
This low-grower is native to the Mediterranean and found on rocky, sloped areas. Leaves are blue-green and the plant reaches around 4 inches tall at maturity. Flowers can be white or pink and bloom in mid-spring through early summertime. This species is best in USDA zones 5-8.

Aethionema grandiflorum (Persian Candytuft, Persian Stonecress)
These limestone-rich soil loving plants are native to Turkey, the southern Caucasus, and northern Iran. This species is gorgeous in gardens, and has pink to lilac flowers that bloom in springtime. Evergreen. Individual plants reach up to 6-12 inches tall with a similar spread. The species is best in USDA growing zones 4a-9b.

Aethionema retsina (Stonecress of Skiros Island)
This critically endangered species is native to, and found only in, Greece. It prefers Mediterranean climates and rocky hills and shorelines amongst shrubby vegetation. This species is not widely available as a garden ornamental outside of its natural range. To 8 inches tall and 16 inches wide at maturity.

Aethionema saxatile (Burnt Candytuft, Candy Mustard)
This species is native to the European Alps, and prefers environments that are rocky and dry. It grows to reach 6-12 inches tall and has a spread of between 8 and 12 inches, forming a low, dense mat of foliage and pink to white flowers in springtime. Best in USDA growing zones 4-8.

Aethionema schistosum (Fragrant Persian Stonecress)
These plants reach 5-10 inches tall and 1 foot wide. This plant has an erect habit, and unbranched stems that hold dense growths of slate-blue leaves. Fragrant flowers are rose-colored. This species does well in USDA hardiness zones 4-8 and is quite drought tolerant, growing in rock gardens, borders, and other small spaces.

Aethionema 'Warley Rose' (Aethionema x warleyense)
This is a neat, compact grower to 8 inches tall and wide. Leaves are blue-green and grow on stems that hold dense blooms of pink flowers. Very commonly grown species, especially great when grown in warmer climates. This species lends its existence to Ellen Willmott, and is named after her garden at Warley Place.

Caring for Aethionema

Aethionema, or Stonecress, will need a spot in the garden that receives full sun; ideally, these plants should be getting between 6 and 8 hours of direct sun each day. When Stonecress are grown in shady conditions, they have a tendency to become leggy and not flower as well. Ensure that soil is well-draining, rich in nutrients, and has a pH of between 6.5 and 7.5 (slightly acidic to neutral). The ideal stonecress soil is light, porous, and sandy or gritty with good lime content. If you would like to create the perfect soil conditions for these plants, combine one part compost with two parts sand and a little limestone added in. Mulch with gravel or small rocks rather than an organic mulch like wood chips to best mimic their natural environment. Water new plantings regularly as they establish themselves in the landscape. At maturity, Stonecress plants are considered to be drought-tolerant, able to get by for most of the year on rainfall alone with supplemental irrigation during extended periods of drought. Waterings should be infrequent but thorough and allow for the soil to dry out in between.

Stonecress plants are native to lean soils, and do not typically need to be fertilized. However, if growth is slow or plants are not flowering, they may benefit from a feeding of an inch of compost around the base of plants in springtime. Pull mulch back before applying, work the compost gently into the soil a bit, water it in, and then replace mulch. Spent blooms can be deadheaded to encourage further flowering, but other than this, the plant does not need much pruning. In springtime, when new growth is starting, the areas of the plant that have faded over wintertime will be apparent, and can be trimmed off. These are short-lived plants in most situations, and will need to be replaced after about two years, but they do self-sow, providing volunteer seedlings that can be dug up and transplanted elsewhere.

Propagation

Aethionema, or Stonecress, can be propagated in two ways: by seed or by cutting. If you are looking to create an exact replica of a plant, use the cutting method of propagation, as propagation by seed does not guarantee a clone of the parent plant. To propagate your Stonecress, follow the instructions below:

Propagating Aethionema by Seed
To propagate via seed, gather the following materials: a bag, a pot (or planting tray), soil that is one part compost, two parts sand with a little limestone added in, and a spray bottle with water. Follow these directions to propagate your Stonecress from seed:

In late summer, leave some of flowers on your existing plant and allow them to come to seed. Remove the seed pod cluster after it has dried, turned brown and some of the seed pods have begun to open and release their contents. Harvest the seeds from the seed pods and place them in a paper bag. This plant can self-sow in the landscape if the conditions are right, but to ensure a new plant from seed, it is best to sow indoors in wintertime. Store your harvested seeds in a cool, dark place until about 10-12 weeks before the last frost of spring in your area.
Prepare your pots or seed trays with your potting mix and water to ensure that good drainage is occurring. Plant more seeds than you want new plants, as not all seeds will germinate. Place your seeds on top of the soil and cover with more potting mix. Water. Place your seed pots or trays in an indoor area that stays around 60 degrees Fahrenheit and receives bright indirect light, or place them in a greenhouse.
The seeds will take between 30 and 90 days to germinate. After the danger of frost has passed in your area, you can transplant the Stonecress seedlings outside.

Propagating Aethionema by Cutting
The best time to take cuttings from an existing plant is in spring or summer. To propagate by cutting, you'll need clean, sharp garden shears, potting mix (one part compost, two parts sand and a little limestone added in), a pot, rooting hormone and a pencil. Once you've gathered your materials, follow these instructions:

Choose an Aethionema plant to propagate. It should be a healthy plant, with new growth and should get some water the night before cuttings are taken. Pick a healthy stem tip that has three or four buds on it and make a 6-inch cutting. Cut quickly and evenly to take the healthiest cutting possible.
Add potting medium to the pot, and give it some water, ensuring that it has good drainage. Make a hole with a pencil in the medium, about two inches down. Dip your cutting in rooting hormone and place it in the hole. Fill in soil around it. Pat down just enough so the cutting stands up by itself. Give it some water.
Keep the soil around your plant somewhat moist as it grows, and ensure that it is in a place that gets bright indirect light and stays at a temperature of between 50-60 degrees Fahrenheit. Once the danger of frost has passed the next spring, it can be transplanted to its forever home in the garden.