German gardener and plant collector born in Lüneburg, Hanover. One of six children, Wallis was deaf from birth and did not speak until he was six years old, at which time his father, a legal advocate, died. Wallis' widowed mother took her six children to her hometown of Detmold, nestled among the mountains and forests of Westphalia. This romantic landscape inspired a love of nature in the young Wallis, who developed a yearning to travel and despite his difficulty with speech learnt several foreign languages.

He briefly took up an apprenticeship with a goldsmith before training as a gardener in Detmold, where he studied botany and went out collecting plants at every opportunity. He then took up a position in Munich, an area in which he loved to roam collecting plants. During this time he made several trips to the Alps, which again renewed his desire to travel. In 1856 he acted upon this wish, embarking on an entrepreneurial venture in Brazil. Unfortunately the business failed when the parent horticultural firm in Germany went b ankrupt, leaving the travelling Wallis without funds. His fortunes turned around in 1858 when he was taken on as a plant collector by Jean Linden of Brussels and he began on an odyssey from the mouth to the source of the Amazon, exploring its tributaries and rich botanical pickings.

Wallis proved his determined character in 1862 when a slow expedition by steamer did not go to plan. Progress up the River Purus was repeatedly delayed by firewood collections for the boilers; it took the steamer over a month to cover 80 miles. The expedition leaders decided to turn back, but Wallis was so keen to continue that he hired a canoe and carried on. His new transport lasted only a few days; being leaky and overloaded, it sank in deep water, along with Wallis's provisions and plants. He did not give up but attempted to travel further in another vessel for a while, (according to an address given by W. Chandless to the Royal Geographical Society in 1866).

Wallis followed up this journey with an adventure across the Andes to Guayaquil and San Buenventura in Ecuador, where he explored the west coast mountains and discovered Odontoglossum cruentum Rchb. f. near Chuquirbamba. While Wallis explored Panama and climbed the Chiriqui volcano in 1867, Linden displayed the orchids his star collector had gathered at the Paris International Exhibition, to much acclaim. Wallis continued his exploits in Colombia, finding a paradise of Melastomataceae and orchids such as Miltoniopsis vexillaria (Rchb.f) Garay & Dunsterville, which he packed in kegs for transportation by mule to Bogota. In 1868 he returned to Europe, where he was awarded honours for his accomplishments and took a well-earned break from arduous travels.

By 1871 he was ready to make another journey, this time to the Philippines in the service of Veitch & Son. The goal of the expensive mission was to locate species of the orchid Phalaenopsis, but, unfamiliar with the islands, Wallis was unsuccessful and the nursery recalled him. He did, however, find one of the largest-growing orchids in the world on the southernmost island of Mindanao, Grammatophyllum speciosum Blume. Sending him back to the familiar ground of Colombia in 1872, he was far more successful, returning with tropical plants such as Anthurium veitchii Mast., which pleased the nurserymen. His engagement at an end, he continued to collect plants over the next few years, making his final journey in the north and central regions of South America in 1875. In Antioquia he was rewarded with the striking Dracula wallisii (Rchb.f.) Luer and Epidendrum wallisii Rchb. f. He was next heard of in Panama, dangerously ill. After recovering enough to return to work, he was again taken ill with fever and dysentery while in Ecuador, where he died in 1878 at Cuença. Wallis was remembered as a courageous and talented collector who introduced more than 1,000 plant species to Europe, many of which were named after him.

Sources:
W. Chandless, 1866, "Ascent of the River Purus", Journal of the Royal Geographical Society, 36: 86-118
J.H. Veitch, 1906, Hortus Veitchii: 62-65.