The Rock Morning Glory, botanically known as Convolvulus sabatius, offers a superb, long-blooming alternative to its aggressive, vining relatives. This plant is a true perennial groundcover, forming a low, trailing mat that rarely exceeds six inches in height. Unlike the annual morning glory vines from the Ipomoea genus, this species is non-invasive and does not require staking or support. Its main appeal lies in its continuous production of bright, lavender-blue, trumpet-shaped flowers, which provide a cooling Mediterranean aesthetic to the garden from late spring until the first heavy frost. The soft, gray-green foliage remains evergreen in mild climates, giving it year-round texture and making it a favored choice for rock gardens, containers, and edges.
Site Selection and Soil Requirements
Successfully growing Rock Morning Glory begins with selecting a site that receives ample sunlight throughout the day. Full sun exposure for at least six hours is necessary to maximize the plant’s vibrant blue flower production, though it can tolerate a small amount of afternoon shade. Placing the plant in a location that mimics its native Mediterranean habitat is the surest path to long-term health.
The composition of the soil is perhaps the most important factor, as Convolvulus sabatius demands exceptionally sharp drainage. It thrives in lean, gritty, or sandy soil and actively dislikes rich, heavy clay that retains too much moisture. To prepare a planting area, incorporate coarse sand or fine gravel into the soil to a depth of at least 12 inches to ensure excess water quickly drains away.
When planting, aim for spring after the final threat of frost has passed to allow the plant a full season to establish its root system. Dig a hole only as deep as the current root ball, but two or three times as wide, and gently place the plant into the prepared, well-draining soil. New plantings will require daily watering for the first few weeks to settle the roots and begin establishment.
Essential Routine Maintenance
Once established, the watering needs of the Rock Morning Glory become modest, reflecting its drought-tolerant nature. It is best to allow the top few inches of soil to dry out completely between waterings, as consistent moisture is the primary cause of root problems. During periods of extreme heat or extended drought, a deep, thorough soaking once a week is generally sufficient to sustain it.
This groundcover performs best in poor soil and requires minimal, if any, supplemental feeding. Over-fertilization, particularly with high-nitrogen products, can encourage lush foliage growth at the expense of the abundant blue blooms. If you feel the need to fertilize, apply a light application of a balanced, all-purpose fertilizer (such as a 10-10-10 ratio) only once or twice early in the spring.
Pruning mainly serves to maintain a tidy shape and encourage the continuation of flowering. Although the plant is self-cleaning, removing spent or faded flowers, a process known as deadheading, will encourage the production of new buds and a fuller display. Trimming back any overly long or “leggy” stems after the main bloom cycle, or in late winter, will help keep the plant compact and prevent the base from becoming overly woody.
Propagation Methods
Multiplying Rock Morning Glory is most reliably achieved through two distinct methods: softwood cuttings and seed starting. Taking softwood stem cuttings is an effective way to produce clones of the parent plant, ensuring the new plants retain the exact flower color and characteristics. In spring or early summer, cut non-flowering stems about three inches long, making the cut just below a leaf node where the rooting hormone is naturally concentrated.
After dipping the cut end in a rooting hormone powder, insert the cuttings into a pot filled with a mix of perlite and peat moss for optimal drainage and air circulation. Keep this rooting medium consistently moist and place the pots in a sheltered location away from direct sun until a viable root system has developed, which typically takes a few weeks.
If starting new plants from seed, you can improve germination rates by scarifying the hard seed coat before planting. This process involves gently nicking the seed with a knife or rubbing it with sandpaper, followed by soaking the seeds in water overnight. Plant the treated seeds indoors four to six weeks before the last expected frost date to get a head start on the growing season.
Overwintering and Troubleshooting
Rock Morning Glory is hardy in USDA zones 8 and 9, tolerating winter temperatures that drop to between 15 and 20 degrees Fahrenheit. In these borderline zones, the foliage may die back, but the woody base of the plant will survive and resprout fresh growth the following spring. Gardeners in colder climates should treat the plant as an annual, or prepare to provide winter protection.
For plants growing in containers, the simplest method for colder regions is to move the pot into a cool, sheltered space, such as an unheated garage or basement, for the winter. Reduce watering significantly during this dormant period, providing only a light monthly drink to prevent the root ball from completely desiccating.
The most common issue encountered is root rot, which stems directly from the lack of proper drainage or overwatering. This can be prevented by ensuring the soil is gritty and that the plant is only watered when the soil has dried out.
If the plant fails to produce its characteristic blue flowers, the cause is usually either excessive shade or too much nitrogen fertilizer, which redirects the plant’s energy into leaf production instead of blooming.