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Moss phlox are the earliest of the species to bloom. In the Appalachian shale barrens P. subulata begins to flower in early April. Seed is ripe and shed by early summer; germination is delayed until the following spring. New vegetative growth is made during the summer and becomes semi-woody by fall. In the late summer roots grow in the branch nodes of last year’s growth and anchor down the stems of the enlarging phlox mat. Other moss phlox species follow this general pattern, although the tendency to form roots from nodes varies, and bloom times depend on the local climate.

In the eastern woodlands Phlox stolonifera and P. divaricata come into bloom a couple of weeks later than the moss phlox. Seed is ripe and shed in early summer, with germination occurring in spring after one or more winters. P. stolonifera winters as an evergreen leafy mat and sends up flowering shoots 15 to 25cm tall from rooted nodes. During the summer P. stolonifera produces runners 30cm or more long that root down at the leaf axils to produce new plant crowns. P. divaricata winters with tufts of erect evergreen shoots 10-15cm tall and produces upright flowering shoots to about 30cm from these. The foliage, especially fertile shoots, of P. divaricata dies down to a variable degree during the summer, with new growth in late summer. Stems that touch the soil tend to root down at the leaf nodes.

Phlox subulata ssp. brittonii, a small moss phlox

Other mid-size phlox like P. pilosa bloom a little later, in mid to late spring. P. pilosa tends to die back to basal growth in winter, the extent of die-back apparently depending on the genetic make-up of the plant and local winter temperatures. The next season’s bloom occurs on new branches from old shoots and new shoots from the base of the plant. Seed is ripe by mid summer, with germination occurring the following spring. There is more foliage growth following bloom, both on fertile shoots and from the base of the plant. These stems remain erect and do not tend to root down in late summer. There are new stems produced from nodes on the roots, so that the plant becomes a widening clump. Other species in this medium size group generally follow this pattern.

The annual species in this group, Phlox drummondii, P. cuspidata, and P. glabriflora are native to Texas and nearby areas. Seed germinate in winter to early spring. Vegetative growth is rapid, with bloom in spring and early summer. Seeds ripen and the parent plants die during the summer, with shed seeds lying dormant until winter rains.

The tall group of phlox bloom during late spring and summer. Most of the species die back nearly to ground level during the winter in western Pennsylvania, with the exception of Phlox ovata, which maintains a low basal clump of foliage on a thick stem, and P. glaberrima ssp triflora, which is evergreen except for its flowering shoots and maintains a clump of foliage up to 30cm or so high. These two species bloom in mid to late spring, with flowering shoots arising from stems that have wintered over. In P. g. ssp triflora there is a tendency for the somewhat lax stems to lie on the soil in late summer; roots form at the nodes, so that a wide, tight clump of foliage results. The other species bloom on new growth from June into July, except for P. paniculata, which blooms from July into September. Seed ripens during the summer and germinates in spring after one or more winters. In cultivation a few seeds germinate during the fall when planted in seed flats. This may be true in nature, too. [next page]

Phlox paniculata, a very large phlox
Phlox divaricata, a mid size phlox
Phlox maculata group hybrid in winter

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