This section is from the book "British Wild Flowers - In Their Natural Haunts Vol2-4", by A. R. Horwood. Also available from Amazon: A British Wild Flowers In Their Natural Haunts.
I. Yellow Balsam (Impatiens noli-me-tangere, L.). 2. Rest Harrow (Ononis spinosa, L.). 3. Hare's Foot Trefoil (Trifolium arvense, L.). 4. Kidney Vetch (Anthyllis Vulneraria, L.).
Yellow Balsam is from 1 to 2 ft. high. The flowers are in bloom from June to September. It is an annual reproduced by seeds.
The flowers are often cleistogamic. In the allied I. balsamina in young flowers the anthers lie on the still closed stigmas, and in-sects visiting the flower are dusted with pollen while they are inserting their tongue in the long spur. In older flowers when the anthers have withered the stigmas are spread out, and touch the same parts of the bee. The flowers are showy and large, but hidden away. Humble bees visit the flowers.
Touch-me-not has its seeds dispersed by its own mechanism. The capsule1 is stretched when ripe, which causes it to split and eject the seeds on the slightest touch.
This is a humus-loving plant, which requires a peat or humus soil, being addicted to a wet aquatic habitat, where it finds a peaty soil mixed with alluvium.
The leaves are infested by a cluster-cup fungus, Puccinia argentata. The moths Elephant Hawk Moth (Chaerocampa Elpenor), Large Twin-spot Carpet (Coremia quadrifasciata), Netted Carpet (Cidaria reticulata), Lygus biriviata feed upon it.
Impatiens, Dodonaeus, from the Latin, means impatient, because of the sudden bursting of the capsule if it is touched when ripe. Noli-me-tangere, Columna, Latin for touch-me-not, means the same thing.
Photo. J. H. Crabtree - Yellow Balsam (Impatiens Noli-me-tangere, L.)
1 It is 5-chambered. The partitions are thin and break away, leaving the central pillar in the middle. In drying, the cells below the epidermis become stretched more than those below. The carpels turn somewhat to the right, or corkscrew-wise. When the capsule opens, the valves roll up like a spring (as in Meadow Vetchling), and are jerked away carrying the seeds (cf. Geranium).
This handsome and curious plant is called Balsam, Quick-in-hand,
Touch-me-not. Coles, in his Art of Simples, says: "A plant called Noli-me-tangere, near which if you put your hand the seed will spurtle forth suddenly, in so much that the unexpectednesse of it made the Valient Lord Fairfax to start, as Mister Robert (Isobart) at the Physick garden in Oxford can tell you". At night the leaves hang pendent, unlike most other plants, whose leaves droop during the day, if at all.
Essential Specific Characters:71. Impatiens noli-me-tangere, L. - Stem branched, slender, leafy, leaves ovate, serrate, peduncles many-flowered, flowers yellow with orange spots, spur recurved, valves of capsule curling when touched.