How Tall Does Phlox Grow?

Size

• Phlox plants achieve a range of different mature heights between 6 inches and 5 feet depending on the species. Taller phlox varieties include garden phlox (Phlox paniculata) with its mature height of up to 4 feet. Low, ground-hugging phlox include the wild blue phlox (Phlox divaricata) that blooms with highly fragrant flowers in spring and the moss phlox or moss pink (Phlox subulata) with its creeping growth habit.

Growth Habit

• The growth habit of phlox plants differs with species. The taller varieties are mostly clump-forming plants that have rigid, firm stems. Taller phlox have an extended bloom time and bloom with large clusters of small sized flowers. The plant clump gets larger every year with new stems appearing around the base every season. Contrary to the taller varieties, low-growing or creeping phlox grows from stolons or underground stems. These stems, produced by the mother plants, lead to dozens of new plants every year. These phlox species grow in a thick, low mat and often self-sow profusely.

Cultural Requirements

• Plant phlox in well-drained, moist, fertile soil for best growth. The plants adapt well to a range of pH levels but are not tolerant of humidity, heat or drought. Amend the soil with peat or rotted oak leaves prior to planting. Avoid planting in clay or rocky soil. Either create a raised bed to plant in problem areas or replace clay or rocky soil with loam. Space plants adequately for good air circulation. Keep soil moist but not wet at all times.

Problems

• Common phlox diseases include powdery mildew. Plants growing in well-ventilated areas and in fertile soil are less prone to the disorder. Thin the larger clumps during spring, leaving no more than five stems per clump, and divide the plants after every three years. Red spider mites are likely pests of phlox. Symptoms include yellowing plants. The pests are common during dry and hot weather. Mist the foliage regularly in the morning to minimize chances of infestation.