Phlox, a favored perennial, offers vibrant blooms and often a fragrant presence in gardens. Propagation, the process of cultivating new plants from existing ones, allows gardeners to expand their displays or share favorite varieties.
Why Propagate Phlox
Propagating phlox offers several advantages for gardeners. It provides a cost-effective way to expand garden beds, filling spaces with beloved varieties without purchasing new plants. This method also allows for sharing plants with friends. Beyond expansion, propagation can help preserve a favorite phlox variety. Rejuvenating older, less vigorous plants is another benefit, as division can often restore their health and blooming capacity.
Propagating Phlox by Division
Division is a straightforward method for propagating clump-forming perennial phlox. The best times to divide phlox are in early spring as new shoots emerge or in the fall, four to six weeks before the first hard frost. Tools required include a sharp spade or garden fork and a clean, sharp knife.
Water the phlox plant thoroughly about 24 hours before division to ensure the roots are hydrated. Carefully dig around the plant’s root ball with a spade, several inches away from the main stems, and gently lift the entire clump from the ground. Once unearthed, gently remove excess soil to expose the root system.
Use a sharp knife or spade to divide the root ball into sections, ensuring each new section has three to five vigorous shoots and healthy roots. Replant these divisions immediately at the same depth as the original plant, with the crown level with the soil surface.
Propagating Phlox by Cuttings
Propagating phlox from stem cuttings is effective, especially using softwood cuttings taken in late spring to early summer. Cuttings are typically 4 to 6 inches long, taken from new, non-flowering growth. Use sharp pruners to make a clean cut just below a leaf node.
After taking cuttings, remove lower leaves, leaving a few at the top to reduce moisture loss. Dipping the cut end in rooting hormone can enhance root formation. Prepare a sterile, well-draining potting mix. Insert the prepared cuttings into the rooting medium.
Create a humid environment by covering pots with a clear plastic bag or humidity dome; this maintains moisture and prevents desiccation. Place cuttings in a bright location with indirect light and maintain consistent moisture in the potting mix.
Propagating Phlox by Seed
Propagating phlox from seed can be a rewarding process. Seeds can be collected from existing plants or purchased. Many perennial phlox varieties require cold stratification to break dormancy.
This can be achieved by sowing seeds outdoors in late fall for natural stratification or by placing them in a refrigerator with a damp medium for 60 days. For indoor sowing, done 6 to 8 weeks before the last expected frost, use a light, well-draining seed-starting mix.
Sow seeds on the surface or cover them very lightly with about 1/8 inch of fine soil, as some phlox varieties need light to germinate. Maintain soil moisture and warmth between 60-70°F (15-21°C) and provide bright, indirect light. Germination occurs within 10 to 21 days for many types.
Caring for New Phlox Plants
Proper care ensures the successful establishment of newly propagated phlox plants. Consistent watering is necessary to maintain even soil moisture without waterlogging. New plants benefit from well-draining soil and thrive in full sun to partial shade.
If seedlings or cuttings were started indoors, hardening off prepares them for outdoor conditions. This involves gradually exposing them to increasing periods of outdoor light, temperature fluctuations, and wind. Once hardened off and after the danger of frost has passed, new phlox plants can be transplanted into their permanent garden locations, spaced adequately for air circulation.
Troubleshooting Propagation Issues
Propagation can present challenges. If cuttings fail to root, common causes include insufficient humidity or using the wrong type of cutting material. A consistently moist, but not saturated, rooting medium and high humidity around cuttings improve success.
Seedlings may succumb to damping-off, a fungal disease characterized by seedlings toppling over. Prevent this by using sterile seed-starting mix, ensuring good air circulation, and avoiding overwatering.
Poor growth in new plants can stem from inadequate light, insufficient water, or a lack of nutrients. Pests like spider mites or diseases such as powdery mildew can also affect young phlox, often exacerbated by poor air circulation or overly humid conditions. Mitigate these issues with proper spacing and watering at the plant’s base.