The ‘Ascot Rainbow’ spurge (Euphorbia x martinii ‘Ascot Rainbow’) is a highly valued perennial known for its striking, year-round color in the garden. This cultivar is particularly prized for its variegated foliage, which features lime-green and blue-green leaves edged in a creamy yellow border. The plant’s mounding, compact habit and dramatic color shifts—deepening to pink and salmon tones in cooler weather—make it a popular choice for adding texture and visual interest to mixed borders and containers.
Establishing the Ideal Environment
The ‘Ascot Rainbow’ spurge performs best in locations that receive full sun, meaning at least six hours of direct sunlight daily. This intensity promotes the most vibrant foliage coloring. While the plant can tolerate partial shade, too little sun results in a less vibrant, greener leaf color.
The most significant factor for this species’ health is the soil, which must be extremely well-drained to mimic its native Mediterranean habitat. This euphorbia thrives in average to poor, rocky, or sandy soil, but it cannot tolerate standing water, which quickly leads to root rot. Amending the planting site with grit or sand helps ensure sharp drainage, especially in areas with heavy clay soil.
‘Ascot Rainbow’ spurge is a hardy perennial, thriving across USDA Hardiness Zones 5 to 9. The plant is considered semi-evergreen, retaining much of its foliage through mild winters. In the lower end of its hardiness range, such as Zone 5, a protected planting location and winter preparation are important to ensure survival through harsh cold.
Watering, Feeding, and Seasonal Pruning
New plants require regular watering during their first growing season to develop a deep root system, ensuring the soil remains moist but not saturated. Once the plant is established, usually after the first year, it exhibits excellent drought tolerance. This makes it a good choice for water-wise landscapes, requiring minimal supplemental watering.
Fertilizer needs for the ‘Ascot Rainbow’ spurge are low, reflecting its tolerance for average or poor soils. Heavy feeding is unnecessary and can lead to weak, overly green growth that compromises the plant’s color. An application of a slow-release, balanced fertilizer in the spring or a light annual top-dressing of compost is sufficient to support new shoots and blooms.
Pruning is primarily maintenance to manage shape and remove spent growth. The plant produces flower clusters that fade by late spring or early summer. These spent flowering stems should be cut back to the ground level or to a healthy side shoot. This maintains a tidy appearance and encourages new, bushy growth, and is best done immediately after the blooms have finished.
When performing any pruning or deadheading, wear protective gloves and eye protection. The stems of all Euphorbia species, including ‘Ascot Rainbow,’ exude a white, milky sap, known as latex, when cut. This latex can cause significant irritation upon skin contact or damage to the eyes.
Safety Precautions and Winterizing
The white, milky sap (latex) released from the plant’s stems requires careful handling. This substance can cause a skin rash, burning, or blistering, especially when exposed to sunlight. Direct contact with the eyes is particularly dangerous, as the sap can cause inflammation and temporary vision impairment.
All parts of the ‘Ascot Rainbow’ spurge are considered toxic if ingested, posing a risk to pets and small children. Site the plant thoughtfully, away from areas where accidental consumption might occur. Proper cleanup of all pruned material is necessary to remove the risk of exposure to the toxic sap.
Preparing the ‘Ascot Rainbow’ spurge for winter is straightforward. In colder climates, particularly Zone 5, apply a generous layer of root mulch around the base of the plant. This helps insulate the root crown from extreme winter temperature fluctuations. While the plant is generally evergreen in warmer areas, this protective measure is beneficial in colder regions, as wet winter soil is often more damaging than the cold itself.