Phlox are beloved flowering perennials known for their long-lasting blooms and delightful fragrance. These plants are not typically grown from true bulbs, but rather established from bare-root divisions or container-grown plants. The following instructions focus on successfully establishing these root-based forms in your garden. Understanding the specific needs of the root systems ensures a smooth transition and rapid growth.
Selecting the Right Time and Location
The ideal time to plant Phlox is during the cooler periods of the year: early spring after the last hard frost or early fall, at least four to six weeks before the first expected frost. This timing allows the roots to establish before the stress of summer heat or winter cold. Bare-root Phlox should be planted immediately upon receipt, usually in the spring.
Phlox performs best in a location that receives full sun, meaning at least six hours of direct sunlight daily. Taller garden Phlox (P. paniculata) can tolerate afternoon shade, especially in hotter climates, but full sun encourages the most vigorous flowering. Lower-growing types like creeping Phlox (P. subulata) thrive best in full sun.
Phlox requires well-draining soil to prevent root rot. If your soil is heavy clay, amend it substantially with a two to four-inch layer of compost or other organic matter, worked 12 to 15 inches deep. This improves drainage and fertility, as Phlox prefers rich and evenly moist soil. Good air circulation is also a consideration, so avoid planting Phlox in overly crowded spaces to help prevent fungal issues like powdery mildew.
Step-by-Step Planting Guide
Begin by digging a hole approximately twice as wide as the root ball or the spread of the bare roots, but only as deep as the root system itself. For container-grown plants, the hole’s depth should ensure the top of the root ball sits level with the surrounding soil surface. If planting a bare-root division, soak the roots in water for an hour or two before planting to rehydrate them.
Before placing a container plant into the ground, gently score the root ball to loosen the roots, encouraging them to grow outward. If planting a bare-root specimen, gently fan the roots out and position the plant so the crown—where the roots meet the stem—is situated right at the soil line. This positioning is critical, as planting the crown too deep can lead to rot.
Backfill the planting hole with the amended soil, carefully tamping it down to eliminate large air pockets that could dry out the roots. Ensure the soil is firm around the roots without being compacted, which inhibits water absorption and root growth. When planting multiple Phlox, space them according to their mature size, typically 18 to 24 inches apart for tall varieties, to maintain adequate air circulation and prevent disease.
Essential Post-Planting Care
Immediately after planting, provide the Phlox with a deep and thorough watering to fully settle the surrounding soil and establish good root-to-soil contact. Saturate the entire root zone until the water begins to drain away slowly. For the first several weeks, consistent moisture is paramount for the plant to successfully establish its root system.
Maintain consistent moisture by watering twice weekly during the first year, particularly during dry spells, aiming for about one inch of moisture per week. Once the plant is established, apply a two to three-inch layer of organic mulch, such as shredded bark or compost, around the base. Ensure the mulch does not directly touch the stem or crown, as this can trap excessive moisture and lead to rot or pests.
Mulching helps regulate soil temperature, suppresses weed competition, and aids in retaining soil moisture. Keep a close eye on the newly planted Phlox for signs of transplant shock, such as wilting. Monitoring the foliage for pests like spider mites or early signs of fungal disease allows for prompt intervention, ensuring the plant thrives.