Encephalartos humilis — the dwarf highveld cycad

Introduction

A small and inconspicuous, clump-forming, evergreen, dioecious, cone-bearing plant, arising from an underground stem, often growing wedged between low rocks, on mountains in Mpumalanga.

Description

Encephalartos humilis is an evergreen, extremely slow growing cycad that can be classified as a long-lived but sensitive species. E. humilis is characterized by a subterranean stem, growing straight below the ground that is only up to 0.3 m tall above the ground, with the stem diameter ranging between 130–180 mm. The stem branches freely from the root stock, producing small clumps at the base. Leaves are 300–500 mm long, shortened, twisted and turned over, with a petiole that is 50–150 mm long. The leaves are greyish green, loosely covered with a dense layer of tangled hairs, becoming hairless at maturity, except for the base of petiole. The rhachis of leaflets is twisted towards the apex, the upper margin entire. Leaflets are covered with greyish, bluish, or whitish waxy coating during its early growth, only 9-nerved on the under surface.

Encephalartos h umilis is dioecious, bearing female cones and male cones on separate plants. The cones are greyish, densely covered with matted woolly hairs. Male cones are 150–200 mm long, 40–50 mm broad with its base tapered. The female cones are circular, about 20–70 mm long and 90 mm in diameter. The seeds are orange-yellow, ovoid, 24–30 mm long and 20-–25 mm wide.

Encephalartos humilis is closely related to Encephalartos lanatus and Encephalartos laevifolius although these two species have much larger and longer leaves and their stems resemble that of a tree in growth.

Conservation status

According to the Red List of South African Plants , Encephalartos humilis is assessed with the conservation status Vulnerable (VU), because it has lost habitat, the wild population is declining and it occurs over a relatively small area. The transformation of its habitat to pine and eucalypt plantations has destroyed about 30% of its natural habitat. Also, illegal removal or harvesting has led to a continuing decline in its population. The lack of natural fires has reduced the production of cones, meaning there is less reproduction taking place. CITES records indicate that the lack of cultivated cycads available for sale for ornamental purposes increases the demand for wild harvesting of these species from Encephalartos genus. So far Encephalartos humilis i s being protected and conserved in a number of nature reserves and conservancies as a way of ensuring their population is protected from extinction and human interference through illegal harvesting.

Distribution and habitat

Encephalartos humilis is native to the mountains of Mpumalanga, in the Lydenburg, Carolina, Machadodorp and Mbombela (formerly Nelspruit) districts in South Africa. It is found naturally growing in subalpine grassland, where it prefers steep grassy slopes, or growing on sandy soils over sandstones, and in many instances it is found growing in between sandstone rocks in grassland. They are usually seen on the east and north-east facing slopes. The natural habitat is receives heavy rainfall and dense mists, which stimulates coning of E. humilis . This species grows in the subtropical biome, which is located between the tropics and temperate zones, and is characterized by warm temperatures and precipitation that occurs mainly during summer.

Derivation of name and history

The name of the genus Encephalartos is derived from the Greek word en meaning ‘within’, kephali meaning ‘head’ and artos meaning ‘bread’, referring to the way some species were cooked and the starchy pith of the stems eaten during famine. The species name humilis is a Latin word meaning ‘humble’ or ‘lowly’, describing its small, flattened stature. This species is commonly known as a dwarf cycad, referring to its very short trunk.

Encephalartos humilis is a species native to South Africa, named by botanist Inez Clare Verdoorn, abbreviated to I.Verd. Encephalartos is a member of Zamiaceae, a family of cycads whose physical appearance is like that of palms and ferns, but they are in actual fact totally unrelated to each other. The cycads are viewed as ‘living fossils’ because of how little these plants apper to have changed from the fossil cycads that grew millions of years ago. Their confusion with palms is easily cleared up, as palms are flowering plants (angiosperms) while cycads are cone-bearing plants (gymnosperms).

Cycads are grouped into three distinctive families, Cycadaceae, Stangeriaceae and Zamiaceae, with Zamiaceae consisting of 8 genera and 150 described species. The genus Encephalartos consists of 68 species which are all endemic to Africa, with South Africa containing the majority of 37 species. This family occurs in the tropical and subtropical regions of the world including Africa. Most plant parts of cycads are extremely poisonous, and when consumed can be deadly to some organisms.

Ecology

The genus Encephalartos has a high species richness of pollinators and there are several interactions taking place between the pollinators and the plants. Beetles are known to be the primary pollinators in cycads. However, there is a need to determine the nature of pollination as interactions between insects and cycads that have evolved over the years. Encephalartos humilis grows in the subtropical biome, on grassy slopes in grasslands seasonal fires frequently occur, resulting in this species having to adapt to a fire-prone ecosystem. This has resulted in their ability to resprout after the stem is damaged. They survive the fire by shielding their buds under the bark, away from the heat and flames, and growing underground. Furthermore, their root system absorbs nitrogen from the air, making it available to the plant and thus allowing it to survive in nutrient-deficient sandy soil. The study by Sugasa et al states that seasonal fires stimulate the release of seeds, germination, and leaf production of E. transvenosus , and formation of cones in E. cycadifolius . While heavy rainfall and dense mists stimulate coning in E. humilis .

Uses

Encephalartos humilis can be used for traditional medicinal purposes and it is used to serve as an ornamental plant in gardens. The outer bark and stems of Encephalartos species is harvested and traded in traditional medicine markets. Local people have used Encephalartos species as a source of starch where the stem is harvested to get edible starch to overcome famine. Due to their unique physical appearance, many cycads are popular ornamentals for garden displays and landscaping designs. E. humilis is small, slow-growing and cones infrequently, and is difficult to transplant successfully. This species is listed on CITES Appendix 1, permits are required for all international trades of any plant material and wild plants may not be traded.

Growing this species

Encephalartos humilis is a sensitive species  that is best cultivated under controlled conditions because it requires frequent monitoring.

They are best propagated sexually, through seeds. Remove the fleshy coat exposing the hard inner shell of a seed prior to sowing them. The seeds are still underdeveloped after removal of the flesh, therefore, store them for a couple of months in cool conditions before sowing. Sow seeds in spring at the start of the growing season, in a sandy soil, slightly cover the seeds, do not bury them as that will hinder germination leading to rotting of the seeds. After sowing, place the seeds in a misted greenhouse, shaded area or cold frame and leave to germinate. They will germinate well where they will receive high temperatures during the day and cold temperatures in the night. They require average watering as sandy soils are aerated supporting the development of healthy root system for emerging seedlings. Generally, cycads are slow growing therefore they can germinate after weeks to years. Once it is germinated, pot seedlings in an aerated potting mix using a narrow pot which allows for continuous development of the roots. During their early growth seedlings are less tolerant to drought and extreme humidity, therefore place the potted seedlings in partially shaded conditions. Apply fertilizer to the potted seedlings to provide nutrients so they will grow faster and produce strong leaves. Thereafter water regularly to prevent seedlings from experiencing drought stress conditions.

Encephalartos humilis does not transplant well, making vegetative propagation difficult to carry out for this species. Regardless, Encephalartos species can be propagated through separating the clumps or suckers from a parent plant. Removing clumps or suckers is carried out in spring or during the growing season when the diameter of the stem is only 5 cm, mainly because that is before the new development of a leaf. Remove using a very sharp knife. Remove any existing leaves on the sucker as they will take up all the energy. Treat the wound on both the mother plant and the sucker using a fungicide and allow them to heal before the sucker is planted. Place the suckers, while they are still healing, in conditions that will prevent drying out,  as drying of a wound will reduce its ability to root while promoting rotting. Once it has healed replant in sandy soil supplying with frequent watering to ensure that they adapt to their new growing environment.