Ornamental grasses are perennial plants prized for their decorative foliage, unique textures, and architectural form. They typically grow in dense, clumping mounds, making them ideal for garden borders or as specimen plants. Propagation creates new plants from existing stock, allowing gardeners to multiply favorite varieties or rejuvenate older clumps. This is achieved reliably through two primary methods, each suited to different species and gardening goals.
Propagating by Dividing Mature Clumps
Dividing a mature clump is the most effective and preferred method for propagating most ornamental grasses, especially dense-mounding types and specific cultivars, as it produces a genetic clone of the parent plant. The best time depends on the grass type: cool-season grasses should be divided in early spring or early fall, while warm-season grasses respond best to division in late spring or early summer, just as new growth begins. Timing the division outside the most intense heat allows new divisions to establish roots with less stress.
Preparation should begin the day before by thoroughly watering the parent plant to hydrate the root mass and make the soil easier to work with. Use a sharp spade to dig a wide circle around the clump, extracting the entire root ball or a sizable section from the outer edge. For large, woody masses, you may need a specialized tool like a root saw, a sharp knife, or two garden forks placed back-to-back to pry the dense crown apart.
The goal is to separate the root mass into smaller sections, ensuring each new division contains a healthy fan of shoots and a robust collection of roots. Inspect the center of the original clump for a woody, dead core, which should be discarded as it no longer supports healthy growth. Divisions must be kept moist and replanted quickly to prevent the roots from drying out. Even small pieces can be successfully grown, although larger divisions establish themselves faster.
Propagating by Starting from Seed
Starting ornamental grasses from seed is necessary for species that do not divide well or when a large quantity of a non-cultivated species is desired. Seeds can be collected in the fall when the seed heads are dry or purchased from a supplier. This method introduces new genetic variations, but many named cultivars are sterile or will not grow true to the parent plant from seed.
Use a sterile, peat-free seed-starting mix in shallow trays or containers. Most ornamental grass seeds should be surface-sown and gently pressed onto the soil, as some species require light for germination. While many species germinate readily, some grasses benefit from cold stratification, which mimics winter conditions and can be achieved by refrigerating the seeds in a moist medium for four to eight weeks before sowing.
Maintain consistent moisture in the seed-starting mix, typically through bottom watering, and keep the trays in a bright location. Germination timing and temperature vary widely; some may sprout in ten days, while others take several weeks. Once seedlings develop their second set of true leaves, they are ready to be moved into individual pots before transplanting outdoors.
Essential Aftercare and Establishment Techniques
Successful establishment is crucial for the survival of newly propagated grasses. Divisions should be planted immediately into their permanent location at the same soil line as the parent plant, with the planting hole being twice as wide as the root ball. After planting, gently firm the soil around the new division to eliminate air pockets and water deeply.
The primary requirement for both divisions and young seedlings is consistent moisture during their initial establishment phase. Divided clumps need regular watering for the first few weeks to support new root growth, while seedlings require careful monitoring to ensure the soil never dries out. Most ornamental grasses perform best in full sun, so selecting a location that receives at least six hours of direct sunlight daily will support robust growth.
Seedlings grown indoors should be gradually hardened off by exposing them to outdoor conditions for increasing periods before final transplanting. A light, balanced fertilizer application can encourage development, but excessive fertilization should be avoided as it can lead to weak, floppy growth. Applying a two to three-inch layer of organic mulch around the base of established plants helps conserve soil moisture and regulate soil temperature, promoting a strong start.