Phlox are popular garden plants, known for their vibrant blooms and ability to add color to landscapes. Understanding their root systems is important for ensuring healthy growth and abundant flowering. Proper root development allows these plants to anchor themselves and efficiently absorb water and nutrients.
Understanding Phlox Root Systems
Phlox plants possess a fibrous root system. This network of fine, branching roots spreads through the soil, effectively anchoring the plant and absorbing moisture and nutrients. Garden phlox (Phlox paniculata) primarily develops a taproot along with small rhizomes, which contribute to its clumping nature rather than extensive spreading.
Creeping phlox (Phlox subulata), in contrast, forms a dense, mat-like root system that is shallow. This allows it to spread along the ground, with stems rooting at the nodes where they contact the soil, forming new plants. This rooting habit makes it effective as a groundcover, creating a carpet of foliage and flowers.
Phlox Root Depth and Spread
Upright garden phlox (Phlox paniculata) develops a taproot and a fibrous root system that can extend to a depth of 12 to 15 inches. These plants typically spread to about 2 to 3 feet wide. The roots form clumps, gradually increasing in size over time.
Creeping phlox (Phlox subulata) has a shallow root system, typically growing only a few inches deep. Its mat-forming habit allows it to spread vigorously, reaching up to 2 feet wide or more. These dimensions can fluctuate based on soil type and growing conditions.
Planting and Transplanting Phlox
When planting or transplanting phlox, preparing the planting hole is important. Dig a hole that is twice the diameter of the root ball and deep enough so the top of the root ball is level with the soil surface. For bare-root phlox, plant the roots between 2 and 4 inches below the ground, with the crown at soil level.
Handle the roots with care to prevent damage. Gently untangle any circling roots, especially if the plant was root-bound in a container, and spread them out in the hole. After placing the plant, backfill with soil, gently firming it around the roots to remove air pockets. Immediately after planting, water the phlox thoroughly to help settle the soil and encourage root establishment. Consistent moisture for the first few weeks is beneficial for strong root development.
Dividing Phlox
Dividing phlox is a beneficial practice that rejuvenates older plants, helps control their spread, and provides new plants for other garden areas. Division is recommended every two to four years, especially when plants show signs of reduced blooming or a sparse center.
To divide phlox, water the plant thoroughly the day before to ensure the roots are hydrated. Carefully dig around the root ball with a sharp spade, lifting the plant from the ground while retaining as much root mass as possible. Gently shake off excess dirt to expose the roots. Separate the root ball into sections, ensuring each new division has healthy roots and several shoots. Replant these divisions immediately at the same depth as the original plant and water them well to help them establish.
Common Phlox Root Problems
Phlox roots can encounter several issues. Root rot is a common problem, caused by poor drainage or excessive watering, leading to waterlogged soil. Symptoms include yellowing leaves, wilting, stunted growth, and darkened, mushy roots or stems. To mitigate this, ensure planting sites have well-draining soil and avoid overwatering.
Root-bound conditions are another issue, which primarily occur in container-grown phlox or neglected garden plants. This happens when roots become so dense they circle within the pot, hindering nutrient and water uptake. When transplanting, untangling circling roots helps prevent this. Spider mites can also affect phlox, impacting plant vigor. Ensuring adequate watering and fertilization can help plants better tolerate infestations.