Plant tenor tall phlox (Phlox paniculata) in your perennial garden in spring and you'll enjoy bright crimson blooms all summer long. Tenor tall phlox, which can grow to heights of 2 to 3 feet and sometimes more, is especially gorgeous when planted behind a variety of smaller annuals and perennials. Tenor tall phlox is a sturdy plant, and with a bit of extra protection, will survive even cold northern climates.
Plant tenor tall phlox in full sunlight. Although tenor tall phlox will grow in partial shade, it won't thrive as it will in full sunlight. Avoid planting tenor tall phlox close to shrubs and trees, which will compete with it for nutrients and moisture in the soil.
Water tenor tall phlox on a regular basis and keep the soil consistently moist. Water at the base of the plant to avoid wetting the leaves. If you water tenor tall phlox overhead, water the plants early in the morning so the plant has time to dry in the sunlight.
Fertilize tenor tall phlox in early spring, as soon as new growth emerges, using a balanced fertilizer for blooming plants. Fertilize tenor tall phlox one more time, just before it is about to bloom.
Spread 4 to 6 inches of organic mulch such as pine needles, straw or bark chips around the base of the tenor tall phlox as soon as the ground freezes in early winter. Mulch will protect the roots from freezing, and will prevent tenor tall phlox from emerging from the soil too early in spring, before the freezing weather has passed. Remove the mulch in spring, because damp mulch can invite disease and fungus.
Divide tenor tall phlox every two to four years, before new growth emerges in spring. Dig the plant with a garden fork, and divide it into four or five sections, each with a healthy root. Plant the divisions in soil that has been cultivated. Give the divisions a boost by mixing 1 to 2 inches of compost into the top of the soil.