Impatiens noli‐tangere L.

Balsaminaceae. A glabrous annual herb, 20–180 cm tall. Stems translucent yellow/green often suffused with red, simple or branched, becoming swollen at nodes; branches of the third order present on well-developed plants. Stems to 2 cm diameter, becoming hollow with age. Roots simple, to a depth of 10–15 cm. Leaves 1.5–10 × 1.5 cm, with 5–8 pairs of lateral veins, opposite becoming alternate, ovate–elliptical to ovate– lanceolate or oblong, base cuneate to subcordate, apex obtuse to acute, mucronate, margin serrate to subcordate, often glandular near base. Teeth 7–16 ( − 20) on each side of leaf, usually mucronate, 2–3 mm deep. Flowers (2–) 3–6 in axillary racemes, some cleistogamous, the others (1.5–) 2–3.5 cm, yellow with small brownish/ red spots. Flower resupinate, being twisted through 180 ° , with 3 sepals and 5 petals. The lower sepal is large (8–) 10–20 × 7–13 mm, almost funnel-shaped, longer than wide, gradually contracted to a nectar-tipped spur. This spur is 6–12 mm, curved, rarely bent through 90 ° or more. The two outer opposite sepals are flat and oblique, green. Upper petal separate, small, broad and hollow with pale glaucous-green vein on back. Remaining 4 petals united into 2 lateral pairs, oblique and irregularly lobed (see illustrations in Ross-Craig (1952) and dimensions in Fig. 10). The dorsal petal forms a characteristic hood over the androecium and the united lateral petals provide a prominent lip for alighting insects. Stamens 5, fused together closely around the ovary, alternate with petals, filaments usually short and inverted–subulate, distant. Anthers short and thick, united around the stigma. Gynoecium of 5 united carpels, 2 to many ovules in each locule, inserted in the inner angles. After flowering, the whole corolla falls from the plant. Capsule 5chambered, c . 1.5 cm, linear, glabrous, containing 1–9 seeds with mass c . 2–6 mg. Seeds obovoid–obpyriform, 4-angled in transverse section, 3.3–4.6 mm long, 1.4– 2.2 mm wide, 0.8–1.5 mm thick; longitudinal ridges, one at each angle, acute to obtuse 0.06–0.2 mm wide, 0.06–0.3 mm high (Anderberg 1994). Impatiens noli-tangere has a variable phenotype, with plants ranging from < 15 cm tall, unbranched and producing 1–10 cleistogamous flowers to > 150 cm tall, with considerable primary and some secondary branching and > 100 chasmogamous flowers (‘broom’ type of Fali ̃ ska 1979). Shade, moisture and nutrient levels may affect the appearance of the phenotypes. The size of the cotyledons is important for the later development of the plant (Falencka 1983). A molecular survey of the genetic affinities of samples in 1999 from the Lake District and North Wales and a reference population from Switzerland was performed using AFLP and ISSR analyses. There was clear differentiation between the populations of I. nolitangere in Wales and those in the Lake District, and between both UK populations and the Swiss population (P.E.H. et al .). Most of the genetic variation was partitioned between rather than within regions and there was little evidence of gene flow between regions. There was little differentiation between metapopulations in the Lake District and a modest estimate of gene flow (N m = 0.61) compared with greater evidence of population differentiation in Wales and a very low estimate of gene flow (N m = 0.13). No varieties have been recorded from the UK, but several have been reported elsewhere. These include var. albiflora Schwarz and var. micrantha Rouy & Fouc. in central Europe (Browicz & Zieli ̃ ski 1976), var. pallescens Nakai from Korea and the Far East (Hong & Oh 1993) and var. parviflora Kitagawa from Japan (Kitagawa 1954). Impatiens is essentially a montane genus of the Old World, containing over 900 spp. (Cullen et al . 1997), half of which occur in the subcontinent of India. Impatiens noli-tangere is the only native Impatiens species in the UK: the introduced I. glandulifera , I. parviflora and I. capensis are also established. Impatiens noli-tangere (touch-me-not balsam) is a scarce native annual of wet woodlands, streams and lakesides, which is locally common in mid-Wales and the English Lake District.