I know I have not done one of these in a really long time but Eliza at Appalachian Feet is having a Blog Carnival about "How to Find Great Plants" for which she asks people submit posts about great plants they would recommendt What better reason could there be for me to finally get back into the habit of writing this type of post? The subject of this new Plant Care Profile is cushion spurge (Euphorbia polychroma), one of my all-time favorite perennials. Neat and practically care-free, it puts on a beautiful show of bright yellow flower heads early in spring before most other perennials come into bloom and continues to look nice for the rest of the summer and fall as a tidy green pillow that provides a nice backdrop for plants blooming later.
My very first specimen of cushion spurge (Euphorbia polychroma) in my family's previous Zone 6a garden in southeastern Michigan, approximately one year after planting
Origin: Euphorbia polychroma is native to Eastern Europe, with a natural range that reaches from Turkey to Ukraine and Western Russia.
USDA Hardiness Zone: Cushion spurge is reportedly hardy to Zone 4a.
A closer look at the bright yellow inflorescences
Size: Individual specimens grow to about 1' (ca. 30cm) tall and up to 2' (ca. 60cm) wide.
Flowering Time: Depending on the local climate, Euphorbia polychroma will begin to flower in mid- to late spring, at roughly the same time as creeping phlox (Phlox subulata) and most tulips. Flowering continues for several weeks, and the bracts surrounding the small real flowers retain their color into early summer even after actual flowering has ended.
Light Requirements: Cushion spurge generally needs full sun but will tolerate some light shade, especially when planted near deciduous trees which leaf out relatively late and therefore allow the plant to receive full sunlight during the main part of its growth cycle in spring. However, plants grown this way might become a bit leggy in summer and not look quite as neat.
One of the flower beds in the front yard of my family's former southeast Michigan home in mid-spring, with Euphorbia polychroma, creeping phlox (Phlox subulata), Ajuga reptans, various tulips, money plant (Lunaria annua), and forget-me-not (Myosotis sylvatica)
Soil Requirements: Cushion spurge happily grows in most garden soils, provided they are well-drained.
Siting in the Garden: Euphorbia polychroma should be planted in a well-drained or even somewhat dry spot in full sun. Due to its relatively low growth habit, care should be taken not to plant it too close to plants that get very tall , since these could suffocate the plant or leave it languishing in more shade than it can put up with.
Care: Cushion spurge really requires minimal care. Young plants may be planted or transplanted any time from mid-spring to late fall. While not necessary by any means, it is generally a good idea to work some compost or organic fertilizer such as bone or blood meal into the soil at the time of planting. Newly planted specimens should be watered well until established, after which point watering or irrigation of any sort should only be needed in times of extreme drought and heat. Plants should be transplanted when very young, since older specimens do not transplant as easily; since they reach their full size in two or three seasons under normal conditions, this should not be much of a hassle. After flowering the plants may be sheared back to prevent self-seeding and to keep them even tidier, though this also is entirely optional. I personally prefer a certain amount of self-seeding and only trim individual plants when they look messy because I like to always back up seedlings of Euphorbia polychroma, be it for new plantings or to replace older plants which, after five or six years or so, have lost some of their vigor. After the foliage dies down in late fall the stems should be trimmed to a height of 2"-3" (ca. 5-7cm) but not lower, since the buds for the next year's growth form along the bottom portion of the stems. Like many plants, cushion spurge also benefits from a light layer of leaf mulch, especially in winter but also throughout the year.
A seedling plant in its second year
Propagation: The easiest way to propagate Euphorbia polychroma is through seed, especially if one lets the plants self-seed in the garden and simply removes unwanted extra seedlings or moves the young plants to the desired locations. In my experience this is the best strategy, since the self-seeding is moderate enough that the plant does not get weedy or invasive. Alternatively, one can collect the seeds - which might require bagging the flower heads before the little fuzzy seed pods are fully ripe to keep them from dispersing - and either start them indoors in early spring or sow them directly in the desired location after the soil has warmed up a bit.
Use in the Garden: Cushion spurge adds lively color as well as volume to the spring garden and is well suited for the front or middle of sunny perennial border. The acid yellow of the normal form combines well with light blue forget-me-nots as well as dark blue Ajuga reptans and various species and varieties of grape hyacinth (Muscari sp.). Throughout the rest of the season, the plant forms a neat, domed cushion of velvety green, though there are also some selections, such as 'Bonfire' which have reddish or purplish foliage that provides more obvious all-season interest.
Sources: http://davesgarden.com/guides/pf/go/825/, http://www.phoenixperennials.com/nursery/plant.php?plantID=2764