How to Grow Phlox Throughout the Season
Growth Habit: Each spring you will see the dormant crown of Garden phlox start to emerge from dormancy and produce small green leaves. Keep the area weed-free and let the phlox just grow. Eventually, tall stalks will begin to shoot skyward from the base of the plant.
After a few weeks of spring sunshine, the Creeping phlox will be covered with colorful blooms. Flowers continue to be produced until the weather turns to summer heat but you might well find a few flowers come back when cooler late summer or fall weather arrives.
Staking: The clump of Garden phlox emerges with bright-green leaves that stay low until spring is well established and then begins to grow upward stems. The stems are quite strong and rarely need staking unless the plant is in an area of high winds or where animals can knock the plant over. If you decide to stake, do so early in the year, when the plant is still low to the ground, rather than when flowers begin to form.
Watering: Although you’ll need to water young plants regularly until they become established, in general, phlox does not require much water. During seasons with regular rainfall, your phlox should not need any extra water from the gardener. This drought-tolerant perennial will struggle with water-logged soil, so practice restraint with your hose!
Fertilizing: An application of general garden fertilizer each spring or spreading a fresh layer of compost or fine mulch over the garden each spring is about all these delightful plants need.
Mulching: The low-growing Creeping phlox emerges around the same time as the Garden phlox, but its whole mat starts to show little green shoots which quickly grow to produce early greenery in the garden. Even in areas where the plant does not go completely dormant, you’ll see bright new growth emerge. For this reason, mulch very lightly, so as not to smother out its needle-like foliage.
Phlox: End of Season Care
Trimming & Pruning: Deadheading the spent flowers of the summer blooming perennial keeps the plants healthy, and snipping off the flowers of the ground cover form keeps it looking neat. If you don’t have time or forget to deadhead or trim, the plants will forgive you and continue to bloom anyway. Each fall, after the frost has killed the top growth of your Garden phlox, trim the top dead growth and add that to the compost pile.
Trim the Garden phlox flowers and put into a vase on the table where they will hold up quite well for four or five days.
Dividing & Transplanting: Divide Garden phlox every 2-4 years in spring, to keep plants healthy and vibrant. Separate plants into sections, roots intact, with at least 3 active offshoots for replanting. Transplant with crowns one inch below the soil surface and eyes (offshoots) facing the sky.
Pests & Disease: Older varieties of Garden phlox can have mildew issues, particularly in areas with warm, humid summers. Plants growing in part shade are more likely to get issues than those in full sun, but even full sun locations cannot stop the mildew appearing on the plant. If you're not planting a mildew-resistant variety, your first line of defense against powdery mildew is to properly space your plants in order to allow for good air circulation. Use a botanical fungicide if the problem is persistent (and/or read the article below). Creeping phlox does not usually have fungal issues.
Learn More: How To Control Powdery Mildew On Garden Phlox.