Pampas Grass (Cortaderia selloana) is a large, ornamental perennial grass highly valued in landscaping for its dramatic, feathery plumes. This species can quickly establish itself, often reaching heights of 10 feet or more, making it a striking garden feature. The plant is generally hardy across USDA zones 7 through 11 and exhibits a fast growth rate once established. Cultivating this impressive grass from seed is an economical method for the home gardener.
Pre-Planting Preparation
The initial step in successfully growing pampas grass involves sourcing high-quality, viable seeds. Pampas grass seeds have a naturally high sterility rate, so purchasing from a reputable supplier increases the chances of germination. Starting the seeds indoors during late winter or early spring offers the seedlings a head start before outdoor planting. This timing allows the young plants to establish strong root systems before summer heat arrives.
Gathering the necessary materials streamlines the process. You will need shallow seed trays or small pots, and a fine, sterilized seed-starting mix to prevent fungal diseases. A clear plastic dome or plastic wrap should also be prepared to cover the trays, as this helps maintain the high humidity levels required for successful germination. Ensure all containers are clean and have adequate drainage holes.
Sowing the Seeds
Begin the sowing process by thoroughly moistening the sterilized seed-starting mix, ensuring it is damp but not waterlogged. Fill the containers to just below the rim and gently level the surface. Pampas grass seeds require light exposure (photoblastism) to initiate germination. Therefore, the seeds must be surface-sown and should not be buried.
Carefully scatter the tiny seeds evenly across the surface of the prepared soil. After sowing, lightly press the seeds into the mix using a tamper to ensure good seed-to-soil contact. This pressure anchors the seed without covering it, maximizing light exposure. Optionally, a thin dusting of fine vermiculite can be spread over the seeds to help maintain surface moisture without blocking light.
Place the tray in a location protected from high winds or drafts that could disturb the lightweight seeds. The next phase involves establishing the environmental conditions necessary for the seeds to sprout.
Nurturing Seedlings
Maintaining high humidity is achieved by covering the tray with the clear plastic dome or plastic wrap. This cover creates a miniature greenhouse environment conducive to germination. A steady temperature between 70°F and 75°F is required to stimulate sprouting.
The trays must be situated where they receive bright, indirect light; supplementary grow lights are recommended when starting indoors. Insufficient light can result in weak, leggy seedlings that struggle to thrive. Germination typically begins within two to four weeks, varying based on temperature and seed quality.
Watering requires a delicate approach to avoid dislodging seeds or damaging emerging sprouts. Misting the surface is one effective method to keep the top layer moist, or bottom watering can be employed. Bottom watering involves placing the tray in a shallow saucer of water, allowing the mix to absorb moisture from below. The dome should be removed immediately once the first seedlings emerge to allow air circulation and prevent damping-off disease.
Transplanting and Establishment
Before moving the young pampas grass seedlings outdoors, they must undergo hardening off. This procedure involves gradually acclimating the plants to outdoor conditions, including sunlight, wind, and cooler temperatures, over seven to ten days. Begin by placing the seedlings outside in a shaded area for a couple of hours daily and progressively increase the duration and sun exposure. Skipping this step often results in transplant shock, which can stunt or kill the young grass.
A permanent planting site should offer full sun exposure for at least six hours daily, as this grass thrives in high light. The soil must be well-draining, since pampas grass is intolerant of soggy roots. Due to the plant’s mature size, which can span up to 12 feet wide, adequate spacing must be considered during transplanting.
When the risk of frost has passed and the plants are hardened off, carefully transplant the seedlings into the prepared outdoor location. Dig holes large enough to accommodate the root ball without bending the roots, setting the plants at the same depth they were growing in the tray. A thorough initial watering immediately after transplanting helps settle the soil around the roots, initiating the first year of growth.