Delphinium exaltatum Ait. - Tall Larkspur

Delphinium exaltatum plant

Family - Ranunculaceae

Stems - To +/-1.5m tall, erect, herbaceous, terete, glabrous, glaucous, green, fistulose, simple.

Delphinium exaltatum stem

Leaves - Alternate, petiolate, fairly evenly and widely spaced along the entire stem, not overlapping. Petioles glabrous or with a few sparse hairs near the apex, to +/-15cm long on the lowest leaves, reduced above, ascending from the stem at about a 60 degree angle. Blades with 3 main lobes, to +15cm broad and long, deep green adaxially, silvery-green abaxially, pubescent above and below, more so below. Veins of the blades impressed adaxially, expressed abaxially. The basal lobes of some of the larger leaves divided again and making the blade appear 5-lobed. All lobes further divided in the apical half. Ultimate lobes acute, entire. Upper leaves reduced, 3-lobed only.

Delphinium exaltatum leaves

Inflorescence - Terminal indeterminate raceme to +/-15cm long. Axis of the inflorescence angled, retrorse pubescent. Pedicels ascending as the leaves. Each pedicel subtended by one linear bract. Bracts pubescent, to +5mm long, -1mm broad. Pedicels tomentose, +/-5cm long, bent and expanded at the apex, with a pair of sub-opposite bracts near the apex. Bracts subulate, tomentose, to 2mm long.

Flowers - Petals 4, dimorphic. The upper two petals expanded at the base and forming a spur, glabrous externally, retrorse pubescent internally, with a long greenish nectary on the ventral side. Base of the petals forming a tube to hold nectar. Apices of the upper petals deflexed, purplish-blue, glabrous, notched for +/-1mm. Lateral petals reflexed in the apical half, bearded with long white hairs, purple, deeply 2-lobed at the apex (the lobes 5-7mm long). Stamens +/-30, from below the carpels. Filaments white, strongly compressed in the basal half, nearly terete in the apical half, sparse pubescent, curling in the apical half, 5-8mm long. Anthers yellow when fresh, quickly drying to a chocolate-brown color, 1.2mm long. Pollen whitish. Carpels 3. Ovaries densely antrorse appressed pubescent (the hairs white), ovoid in flower, 2-2.3mm long in flower, +/-1mm in diameter, unilocular, with 4-5 ovules. Styles white, glabrous, to 2mm long. Sepals 5, irregular, the uppermost sepal forming a tube around the spurred petals. The spur to -1.5cm long. Other sepals -1cm long, 5-7mm broad. The lateral 2 sepals rounded at the apex and with a greenish-white spot in the center. The lower 2 and uppermost sepal acute at the apices and with a green spot at the apex. All sepals tomentoulose externally, glabrous internally.

Delphinium exaltatum flowerCorolla close-up.

Delphinium exaltatum spurSpur.

Flowering - July - August.

Habitat - Limestone or cherty limestone north and/or west-facing wooded slopes along the Current and Jack's Fork Rivers.

Origin - Native to U.S.

Other info. - This striking plant has currently only been found in two southern Missouri counties. The plant is locally abundant where it is found, however. This species is the tallest of the genus in Missouri and certainly deserves a place in cultivation.

Photographs taken at the Sunklands Conservation Area, Shannon County, MO., 7-21-04.


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