Woodland Phlox, Phlox divaricata – Grasp Gardener Program

Woodland phlox in habitat in a maple woods in southern Wisconsin.

Woodland phlox, Phlox divaricata, is an jap North American native more and more supplied as a decorative to make use of in cultivated gardens for its enticing bluish flowers. This herbaceous perennial within the phlox household (Polemoniaceae) will be discovered rising in dappled shade in open woods, partially shaded meadows, and alongside stream banks from Quebec to Florida and west to Texas and the Rockies. This plant, additionally generally is referred to by different widespread names together with blue phlox, Louisiana phlox, wild blue phlox and wild candy William, is hardy in zones three to eight. It’s taller and has a extra open behavior than the quite common, sun-loving creeping phlox or moss (P. subulata) and doesn’t unfold as shortly as that species does. One other woodland species, P. stolonifera additionally referred to as creeping phlox, is way shorter at solely 6-Eight inches tall, kinds dense clumps, has oval leaves and fewer lavender to pink blooms within the flower clusters, and is simply hardy to zone 5.

Phlox stolonifera (L and cultivar ‘Sherwood Purple’, LC) is shorter than P. divaricata. P. subulata, together with the cultivars ‘White Delight’ (RC) and ‘Sweet Stripe’ (R), is shorter, extra compact and desires full solar.

Woodland phlox grows from a shallow root system, slowly spreading over time (divaricata way “with a spreading and straggling behavior”). This is without doubt one of the solely Phlox spp. to have each fertile (flowering) and infertile (non-flowering) shoots. The basis system produces stolons which turn into non-flowering shoots because it kinds a unfastened mat of foliage as much as a foot excessive. Stems are furry and sticky (from glandular hairs) with reverse, sessile, furry, lance-shaped to elliptic leaves as much as 2” lengthy with whole margins organized in broadly spaced pairs. The leafy shoots will root on the nodes in the event that they flop onto the bottom, additionally rising the unfold of the colony. The largely unbranched flowering stems are typically longer (to 15 inches tall) and extra densely furry than the infertile shoots, and the leaves on the infertile shoots are typically wider with extra rounded ideas and fewer furry. The flowering stems die again after seeds are produced, leaving a rounded mound of semi-evergreen (in delicate climates) darkish inexperienced foliage to supply and retailer power for the event of the next yr’s flowering shoots. When not in bloom the plant is pretty nondescript and notably because it begins to say no in summer time may very well be mistaken for a weed.

Woodland phlox shoots in spring (L and R) and closeup of leaves (LC) and furry foliage (RC).

For a couple of month in late spring to early summer time crops produce unfastened clusters of salverform flowers on the stem ideas. Every tubular flower, 1-1½ inches large, has 5 flat, petal-like lobes on the finish and a furry inexperienced or reddish inexperienced calyx with 5 linear enamel. The spreading lobes could also be notched (subspecies divaricata, typically within the jap a part of the vary) or whole (subspecies laphamii, typically within the western a part of the vary). There are 5 stamens and a single pistil recessed contained in the slim corolla throat so usually are not readily seen. The sweetly aromatic flowers are available in shades of blue from pale lavender to violet-blue, and infrequently pastel pink or white. The showy flowers appeal to butterflies, moths, bees, and flies.

Flowers are produced in unfastened clusters (L two) from furled buds (LC) and could also be varied colours (R three).

The flowers (which require cross-pollination to supply seed) are solely pollinated by long-tongued bugs together with butterflies (particularly tiger swallowtails), skippers, hummingbird clearwing and sphinx moths, and bumblebees that are in a position to attain the nectar produced on the base of the lengthy tube, however the flowers are visited by many different bugs that feed on the pollen produced close to the top of the tube. Flowers could also be adopted by rounded fruits that begin out inexperienced and finally dry to brown ovoid seed capsules that finally cut up to launch a number of small black seeds. This plant will self-sow, however it’s not aggressive and undesirable seedlings are simply pulled up or transplanted.


After flowering the petals are shed (L) and if pollinated a capsule is produced (LC) with every of the small capsules (RC) finally splitting to launch the small black seeds (R).

Phlox divaricata in a woodland backyard with pink trillium.

Use woodland phlox in native woodland gardens, naturalized areas, or the entrance of casual borders and in shady rock gardens. Interplant with early spring bulbs to assist disguise the senescing bulb foliage. Use alongside a path or close to a window the place the beautiful scent will be appreciated when they’re in bloom. This species can be utilized as a unfastened floor cowl, however is just not dense sufficient to outcompete most weeds. It goes properly with earlier-blooming spring woodland ephemerals similar to bellwort, bloodroot, Jack within the Pulpit (Arisema spp.), and trilliums. Mix it with different shade-loving crops similar to small to medium hostas, astilbes, bleeding coronary heart, columbines, hellebores, heucheras, lungwort and ferns the place it’ll unfold in and across the different crops, then fade into the background after flowering.

Woodland phlox does finest in partial shade and moist, wealthy, well-drained soil.

As its widespread identify suggests, woodland phlox does finest in woodland circumstances in partial shade and wealthy, moist, well-drained soils. However it is vitally adaptable and can tolerate dry and clay soils, and is even drought tolerant as soon as established. Though partial shade is finest, it’ll tolerate full solar in cooler climates. Mulch flippantly to retain moisture and preserve the roots cool by the summer time. Prune after flowering if desired to tidy the plant’s look, however wait till spring to wash up the clump, solely eradicating winter-damaged foliage. This plant has few pest issues, apart from powdery mildew. Putting in areas with good air circulation and slicing the stems again after bloom can assist cut back powdery mildew. Spider mites is usually a downside in scorching, dry climate. Deer and rabbits will browse the foliage.

Woodland phlox is propagated by seed, division (detach rooted stems in spring or early fall), basal cuttings taken in spring, or root cuttings taken in early fall. Seeds will be sown in spring or in mid-summer as quickly as it’s ripe.

A number of cultivars can be found together with:

– Susan Mahr, College of Wisconsin – Madison

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