central spike, in contrast to the wild form, where the flowers only appear on one side. Numerous cultivars have been developed with a range of colours. Seeds are frequently sold as a mixture (e.g. Excelsior hybrids, in shades of white, pink and purple). Some strains are easily grown by the novice gardener, while others are more challenging. They may also be purchased as potted plants in the spring. The following selections have gained the Royal Horticultural Society's Award of Garden Merit: Camelot Series: 'Camelot Cream' 'Camelot Lavender' 'Camelot Rose' 'Camelot White' Dalmatian Series: 'Dalmatian Crème' 'Dalmatian Peach' 'Dalmatian White' D. × mertonensis (the strawberry foxglove) D. purpurea f. alba 'Martina' 'Pam's Choice' 'The Shirley' (Gloxinioides group) Digitalis purpurea is hardy down to (USDA zones 4–9). Toxicity Due to the presence of the cardiac glycoside digitoxin, the leaves, flowers and seeds of this plant are all poisonous to humans and some animals and can be fatal if ingested. The main toxins in Digitalis spp. are the two chemically similar cardiac glycosides: digitoxin and digoxin. Like other cardiac glycosides, these toxins exert their effects by inhibiting the ATPase activity of a complex of transmembrane proteins that form the sodium potassium ATPase pump, (Na+/K+-ATPase). Inhibition of the Na+/K+-ATPase in turn causes a rise not only in intracellular Na+, but also in calcium, which in turn results in increased force of myocardial muscle contractions. In other words, at precisely the right dosage, Digitalis toxin can cause the heart to beat more strongly. However, digitoxin, digoxin and several other cardiac glycosides, such as ouabain, are known to have steep dose-response curves, i.e., minute increases in the dosage of these drugs can make the difference between an ineffective dose and a fatal one. Symptoms of Digitalis poisoning include a low pulse rate, nausea, vomiting, and uncoordinated contractions of different parts of the heart, leading to cardiac arrest and finally death. Medicinal use Extracted from the leaves, this same cardiac glycoside digitoxin is used as a medication for heart failure. Its clinical use was pioneered by William Withering, who recognized it "reduced dropsy", increased urine flow, and had a powerful effect on the heart. During World War II, County Herb Committees were established to collect medicinal herbs when German blockades created shortages; this included Digitalis purpurea which was used to regulate heartbeat. Gallery See also List of poisonous plants References Bibliography Flora Europaea: Digitalis purpurea Ecological flora