Propagating the Green Alkanet (Onosma viridis): A Gardener’s Challenge
Introduction:
Onosma viridis, commonly known as Green Alkanet, is a captivating herbaceous perennial prized for its striking, vibrant green flowers – a rarity amongst the genus Onosma, which typically boasts yellow or blue blooms. Its somewhat sprawling habit and tolerance of dry conditions make it a desirable addition to rock gardens, gravel gardens, and other low-maintenance landscapes. While its popularity amongst gardeners is growing, propagating Green Alkanet presents unique challenges, making successful cultivation all the more rewarding. The plant’s relative scarcity also contributes to the intrigue surrounding its propagation.
Seed Germination:
Currently, there are no known reliable methods for seed germination propagation of Onosma viridis. While seeds may be produced, their viability is extremely low, and germination rates, even under ideal conditions, are reported to be near zero. Extensive experimentation would be required to determine if specific pre-treatments, such as stratification or scarification, could improve germination success.
Cuttings:
Propagating Onosma viridis through cuttings offers a more promising approach than seed germination.
Challenges: Rooting cuttings can be difficult. The success rate is highly dependent on factors such as timing (ideally taking cuttings in early summer from semi-hardwood), the use of rooting hormone, and maintaining consistently high humidity levels.
Practical Tips: Take 8-10cm cuttings from non-flowering stems, removing lower leaves. Dip the cut ends in a rooting hormone powder and plant them in a well-draining propagation mix (e.g., a mix of perlite and peat moss). Maintain high humidity using a propagator or by covering the cuttings with a plastic bag. Ensure good air circulation to prevent fungal diseases. Consistent, but not excessive, moisture is crucial.
Rewards: Successfully rooted cuttings offer a relatively quick way to increase the number of plants. While genetic diversity is not as broad as with seed propagation, it’s a reliable method to multiply desirable existing plants.
Division:
Division is another potentially viable propagation method for Onosma viridis.
Challenges: Onosma viridis doesn’t readily form dense clumps like some other perennials, limiting the opportunities for division. Divisions need to be relatively large with established root systems to ensure sufficient vigor for survival. Disrupting the root system can cause stress, potentially leading to plant decline.
Practical Tips: The best time to divide is in spring or early autumn, after flowering. Carefully lift the plant and gently separate it into large sections, ensuring each division has healthy roots and shoots. Plant the divisions immediately in well-prepared soil, providing adequate moisture until they establish.
Rewards: Division is a reasonably straightforward method when the plant allows for it, providing a quick way to increase plant numbers while maintaining the genetic characteristics of the parent plant.
Tissue Culture:
Tissue culture propagation of Onosma viridis has not been widely documented.
Challenges: Establishing a viable tissue culture protocol for this species would require significant research and expertise. Developing suitable media formulations and sterilization techniques for Onosma viridis would present a steep learning curve.
Practical Tips: This method is not recommended for amateur gardeners due to the specialized equipment and expertise required. Professional laboratories with experience in plant tissue culture are necessary.
Rewards: Tissue culture offers the potential for large-scale propagation and the elimination of diseases. However, the high initial investment and specialized knowledge make it impractical for home gardeners.
Conclusion:
Propagating Onosma viridis presents a challenge for even experienced gardeners. While seed germination proves unreliable, cuttings and division offer more viable, albeit not always straightforward, paths to success. The rewards of successfully cultivating this unique plant, however, far outweigh the difficulties. The vibrant green flowers, the satisfaction of achieving propagation against the odds, and the knowledge of nurturing a relatively rare plant add to the special charm of owning Green Alkanet. Don’t be discouraged by initial setbacks – persistence, patience, and attention to detail are key to eventual triumph in propagating this delightful plant. Remember to focus on providing ideal conditions, learning from each attempt, and enjoying the journey as much as the destination.