Should there ever be a second edition of the book, here are a few plants I'd want to include. Tennessee distribution: Atlas of Tennessee Vascular Plants, Vol. 1 and 2.
Euphorbia marginata – Snow-on-the-mountain
(Euphorbiaceae – Spurge Family)
This annual is an old-fashioned garden favorite featuring leaves and flower bracts that can be remarkably showy. Though small the flower bracts are snow-white and the clustered flowers appear continuously all summer. Stem leaves are elliptic with thin white margins, and the smaller crowded leaves just below the inflorescence are often mostly to entirely white. Plants grow about two feet tall. While attractive for the garden, snow-on-the-mountain can self sow to the point of weediness, and the plants can become somewhat rangy as the season progresses. Sow seed in place in the spring. This Euphorbia species is native to the plains states and prairies but has escaped cultivation in the east and may be found virtually throughout the United States. It has been documented in the wild in five Tennessee counties.
Heliopsis helianthoides – Oxeye, Smooth Oxeye, False Sunflower
(Asteraceae – Aster Family)
From July to September oxeye produces many bright yellow to golden blooms branching individually on slender stalks. The plant is clumping in habit and grows 3 to 5 feet tall with opposite, ovate, toothed leaves often rough to the touch. Both the ray and disk flowers are yellow, and both produce seed - something true sunflowers don't do as their ray flowers are sterile - thus the "false sunflower" common name. Blooms typically have 9 to 18 ray flowers, but semidouble and double flowers are common and numerous cultivars exploit that tendency. The cultivar 'Loraine Sunshine' has dramatically variegated foliage. Heliopsis begins blooming earlier than most sunflowers (Helianthus spp.), which typically bloom late summer to fall, and does best in good, moist soil with full sun to part shade. Oxeye grows readily from seed and will take poor, dry conditions, but plant quality may be variable. Cultivars take advantage of the species' growth habit, long blooming period, and flower appearance to provide choice selections for the perennial border. The cultiver 'Summer Sun' is pictured. Oxeye is found broadly over the eastern U.S. and plains states and is statewide in Tennessee though lightly in the western third.
Silene caroliniana – Wild Pink, Sticky Catchfly
(Caryophyllaceae – Pink Family)
Wild pink is a showy little wildflower with a complex taxonomy. The plant has semi-evergreen, narrowly oblanceolate foliage 2 to 4 inches long clustered together in low-mounded tufts. In late spring (late April, early May) thin stems with opposite leaves are topped by clusters of brilliant light to dark pink flowers with five wedge-shaped petals slightly notched on the end. It might be mistaken for phlox, but wild pink's petals are separate rather than fused into a corolla tube. These colorful little plants rarely exceed a foot in height but are often covered with bright blooms. Generally a gardener can leave taxonomic issues to trained botantists (Don't try this at home!), but in the case of Silene caroliniana it could prove helpful to know a little more. Few gardening sources acknowledge them but apparently there are three recognized varieties or subspecies of Silene caroliniana: S. caroliniana var. caroliniana, South Carolina wild pink; S. caroliniana var. pensylvanica, northern wild pink or Pennsylvania catchfly; and S. caroliniana var. wherryi, Wherry's catchfly. [Whether they are listed as varieties (var.) or subspecies (ssp.) depends on the naming authority followed. The two terms are typically viewed synonymously.] Var. caroliniana is found in acidic, sandy soils in the southern Atlantic Coastal Plain. The leaf surfaces are hairy and the end of the leaf is more obtuse. Var. pensylvanica is found in the Appalachian Highlands from New Hamphire to Tennessee, usually in rocky woods on limestone-derived soils. Its leaves are smooth on the surface and have a more acute tip. Var. wherryi is found in the Ohio Valley, Alabama, and Missouri and prefers rocky, limestone soils too. Supposedly the calyx differs in detail from the previous variety. These different varieties could become significant in culture. Obviously all three require good drainage, but soil pH and perhaps even climate, particularly summer heat, could affect the plant's success depending on which variety you have purchased. Any of them would make a good rock garden plant, though some shade might be advisable depending on your location. Like its cousin, Silene virginica - the fire pink, wild pink can be short-lived but may be propagated by seed or division.
Croton alabamensis – Alabama Croton
(Euphorbiaceae – Spurge Family)
For gardeners who love the unusual, Alabama croton is a true specimen. This globally rare shrub has much to recommend it in the landscape. The leaves and twigs are liberally dotted with silvery scales and the undersides of the leaves are silvery white. When crushed the leaves produce a fruitlike aroma similar to apples. The foliage is semi-evergreen further south and in more temperate areas provides a steady progression of leaves turning a pleasing orange throughout autumn before falling. Clusters of small yellow-green flowers bloom in early spring on the tips of twigs and quickly develop into green, three-segmented capsules. Native to limestone bluffs, Alabama croton will grow in dry, poor, alkaline soil and easily braves hot summers. It gets 4 to 7 feet in height with an open to broadly rounded shape. Despite its tough natural haunts, Alabama croton takes well to moist, well-drained organic soil and seems to prefer a little shade. Croton alabamensis (var. alabamensis) has been documented in only one Tennessee county, but has not been seen there in several years. Thus it is listed as "Endangered - Possibly Extirpated" in the state. It is also found in Alabama, and there is a similar plant, Croton alabamensis var. texensis (Texabama croton), found in Texas. It may take quite a bit of leg work or web surfing to find one for sale. Alabama croton sometimes appears in rare plant auctions.