Helianthemum nummularium

( hee - lee - ANTH - em - um       num - yew - LAIR - ee - um )

At-A-Glance Information

Also called Sunrose or Common Rockrose, this evergreen shrub requires full sun and moderate water. Native to Europe and Asia Minor, all forms grow about 6-8 inches tall and 3 feet wide. Depending on the species leaves can be grey on both sides, or green on top and fuzzy grey underneath. Single or double white, red, apricot, orange, yellow, pink, rose, peach, or salmon colored flowers bloom in midspring to early summer. Great for planting on slopes, in containers, and by the sea, and also great as a groundcover. ​Helianthemum nummularium grows best in zones 2b-9 and 14-24. ​To find your zone, click here: Zone Map. This species is in the genus Helianthemum, which is a member of the plant family Cistaceae. and the genus name is derived from the Greek words for sun (helios) and flower (anthemom).

Caring for and pruning Helianthemum nummularium shrubs

Plant these shrubs in alkaline, rocky or sandy soils that are well-draining. Once established, these plants are drought-tolerant and will not need much in the way of additional water other than occasional rainfall. These shrubs appreciate a winter mulching to keep roots safe from freezing temperatures. Space 2-3 feet apart if growing as a groundcover. These shrubs do not need fertilizing. Deadhead as flowers fade, and after flowering period give the shrub a light pruning to keep it looking neat. These shrubs will probably need to be replaced every few years, even if pruning is kept up.

Propagation

Helianthemum nummularium can be propagated either by using cuttings or from seed. To ensure that your propagated plant will have the exact same qualities and characteristics as the parent plant, use the 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. To propagate your shrub, follow the instructions below:

Propagating Helianthemum nummularium by Cutting
  1. 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.
  2. In spring or 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 6 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.
  3. 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. 
  4. 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 shrub.

Propagating Helianthemum nummularium by Seed
  1. 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. 
  2. Harvest your seeds.
  3. 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 7-14 days 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.
  4. 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 55 and 70 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.

Problems and Pests

Rockrose is not commonly bothered by pest or disease, as long as roots are not water-logged.
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Gallery

Use these shrubs in rock gardens, allowing their flowers to spill over walls.
The flowers will attract pollinators to your garden.
These shrubs do well in areas of the garden that are not formally irrigated.

Videos

All about growing Common Rockrose.
Rock Rose in the garden.

Resources

Helianthemum nummularium
Wikipedia: Helianthemum nummularium
The New Sunset Western Garden Book: The Ultimate Gardening Guide (2012) - Page 355, Helianthemum nummularium
If you have any questions, comments, concerns, or photos you’d like to add to the gallery, please let me know by sending me a message using the button below!
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