Some species are cultivated as ornamental plants, for example Agave americana L. and certain Yucca L. species. Others, such as the mother-in-law's tongue (Sansevieria trifasciata Prain), Cordyline Comm., and Dracaena Vand. species are widely grown as house plants.

Human contact with many species is close and repeated because of their economic value. Several species, including Agave sisalana Perrine, Phormium tenax Forster & G. Forster, and several Furcraea Vent. and Yucca L. species yield useful fibre.

Mescal, the popular liquor of Mexico, is a brandy distilled from the fermented mash of the cooked stems of certain wild and cultivated Agave L. species, especially A. tequilana A. Weber, A. pacifica Trel., and A. palmeri Engelm. The abundant sap obtained after cutting off the young flower buds of A. atrovirens Karw. (syn. A. salmiana Otto), and possibly other species is fermented to produce an alcoholic beverage known as pulque from which mescal may also be distilled (Purseglove 1972, Bahre & Bradbury 1980).

The steroidal saponins of certain Agave species are used commercially as precursors in the production of medicinally used steroids.

Bowenia, like Stangeria, has distinctive foliage. The two species of Bowenia, named for George Bowen, the first Governor of Queensland, are currently restricted to three small areas of tropical north-eastern Queensland: B. spectabilis in the northeast in the vicinity of Cairns, and B. serrulata farther south, in the vicinity of Rockhampton, also Bowenia sp. Tinaroo from the Tinaroo Hills of the Atherton Tablelands of N-E Queensland.

The stem of Bowenia is always subterranean and rather cylindrical, though variable in shape and size. Its main characteristic, not normally found in other genera, is that it is divided at the apex into several or many short branches, each of which may bear a terminal cone or leaves (or both) and a few cataphylls.

The cones of Bowenia resemble those of Zamia. Male cones are cylindroid and up to 7 cm long and 5 cm wide: female cones are ovoid and up to 15 cm long and 10 cm wide. The latter are dark-green and borne on short, fleshy peduncles; they have peltate, hexagonal sporophyll shields that fit rather closely together when young, but when mature separate widely to expose the large, purple seeds.

All species of Ceratozamia are basically trunking, though the stems are rarely more than about 1 metre tall. The unbranched trunks, often leaning or curved, are covered with stout, persistent leaf bases and cataphylls. A seedling rapidly develops a large taproot that persists and enlarges further as the plant matures. Many fibrous branch roots are present, as well as coralloid roots, the latter containing cyanobacteria and therefore of a bluish green cast.

The leaves in this genus are often long and curving, approaching 3 metres in C. mexicana, and always once-pinnately compound. Except in C. kuesteriana, both rachis and petiole are armed with sharp prickles.

Ceratozamia cones are the most distinctive feature of the genus. They are rather variable in size: those of C. mexicana are large, the female cones being about 45 cm long by 10 cm in diameter; the male cones of C. mexicana are slender and become very elongate and recurved at the time of pollen shedding, when they may attain a length of about 60 cm. Pollen maturation occurs in October in cultivated C. mexicana, and fertilisation occurs in late January and early February. The female cones become mature in June and July, some 6 to 7 months later, when greenish yellow seeds are shed.

Cycas is generally recognised as the most distinct of all living genera of cycads and its reproductive organs are considered by some authorities to be the most primitive in this very ancient group of plants.

Cycas is the most widely ranging cycad genus and its species occur naturally from the southern tip of Japan through the Malay Archipelago, Guam and the mainland of South-east Asia as far as Central China, west through parts of southern western India and Sri Lanka, and as far as Madagascar and the eastern African coast. The range also extends south through the Philippines and Indonesia and eastward of new Guinea, Solomon Islands and the northern half of Australia.

All members of the genus have an above-ground stem, usually but not always forming a trunk which in older specimens of some species (e.g. C. angulata) may reach a height of 8 – 10 metres and in older specimens of other species (e.g. C. circinalis, C. revoluta) is often branched. The outward appearance of the trunk is very similar to that of many other trunking cycads,
The leaves of larger species of Cycas may reach a length of 3 metres.

In other ways, Cycas is the most structurally and genetically distinct genus in the Cycadales. The leaves and stems have certain peculiarities, but the most characteristic and unique feature is the apparently primitive nature of the reproductive organs. Unlike their counterparts in other genera, the megasporophylls of Cycas do not form a determinate female cone, although they are somewhat tightly clustered together when first emerging. After pollination, the megasporophylls of certain species relax and spread out like leaves, then hang down, and eventually, after the seeds ripen and are shed, and fall off the plant individually.

Knowledge of the Mexican and Honduran cycad Dioon (‘two ova’) stems principally from the studies and explorations of Charles J Chamberlain, whose first visit to Mexico was in 1904.

While individuals of D. spinulosum may attain a height of 16 metres, more typical individuals run 3 – 6 metres tall and other Dioon species are lower. Dioon edule, for example, seldom reaches a height of 3 metres and it is usually in the 1 – 1.5 metre range.

Most cycad stems show little wood in cross sections, but older stems of Dioon display a zone of xylem 8 – 10 cm thick; the bulk of the stem is composed of thick zones of starch-laden pith and cortex.

Typical of all species of Dioon are non-articulated leaflets, broadly inserted along the leaf rachises and Dioon is thus the only New World cycad having non-articulated pinnae. The leaves of the closely related D. spinulosum, D. rzedowskii, and D. mejiae are on the order on 2 – 3 metres in length, somewhat, lax and a glossy dark-green, with up to 120 leaflet pairs per frond. Those of D. spinulosum are equipped with marginal spines, as the species name implies, though this character is somewhat variable; the leaflets of D. rzedowskii and D. mejiae are entire (ie smooth-margined). Other species of Dioon are generally of a lower stature, with stiff fronds and sharp-pointed leaflets, which depending on the species, may or may not have marginal teeth.

Females of D. spinulosum (and probably D. mejiae, whose female cones have not been described) produce very large, pendant cones, among the largest in the Cycadales.
Mature female cones of these species measure up to 60 cm in length and 27 cm in diameter; those of other Dioon species are smaller and semi-erect.

Encephalartos gets its name, translated as ‘bread-head,’ from the use of its cones and seeds as food by African aboriginals. Its species are found throughout Africa south of the Sahara, ranging from north of the Equator on both coasts, through the central tropical regions bordering the Congo River, and south-eastward to the extreme southern coast of Cape Province. Currently about 55 species are recognised, but new species are still being described and the total may eventually reach 65 or so.

Certain species of Encephalartos have rather small, subterranean stems but others have massive aerial trunks, several to nearly 10 metres tall when mature, always protected by a sturdy covering of old leaf bases and cataphylls. Although most all of the species have a tendency to produce basal suckers when old, so that in nature the plants sometimes occur in clumps.

The leaves of Encephalartos frequently are leathery and very stiff, characters associated with arid conditions.

The cones of both sexes are frequently long and heavy, sometimes solitary but more often several in number.

In many species the mature cones are brightly coloured in red, orange, yellow, or green. Seeds of Encephalartos are eaten by monkeys (baboons) and birds, all of which have colour vision.

L. hopei is the tallest of all cycads, with erect trunks up to 18 metres high and up to 40 cm in diameter. The trunks are heavily clothed in leaf bases, and cataphylls, the latter structures being produced in much greater profusion than in Macrozamia. This characteristic gives the trunk a strongly armoured appearance, which no doubt suggests the generic name, ‘scale-zamia’.

The leaves of Lepidozamia are 40 or more in a crown, each about 2+ metres long and bearing about 80 recurved leaflets inserted on the side. The leaflets, glossy dark-green, have parallel veins, lack a midrib, are straplike with a smooth edge, and are slightly drooping.

The female cones of Lepidozamia are very large (up to 60 cm long, 20 cm wide) and may weigh as much as 40 kg. The male cones of Lepidozamia are usually more than one, about 20 cm long, and stalked.

Macrozamia (large ‘Zamia’) is a fairly large genus in terms of numbers of species, 27 at present count, but is confined to Australia, where it occurs mainly in the subtropical regions and in areas with a Mediterranean climate.

A few species, such as Macrozamia moorei have large, unbranched, aerial trunks as much as 5 metres tall, and from a distance can appear very palmlike, but in others the stem is mainly or wholly subterranean, though in all cases covered with persistent leaf bases and relatively few cataphylls. In large species, the general appearance of old plants, even within a comparatively local area, can be quite variable, because in deep, soft soil the plant’s contractile roots can slowly drag the stem into the ground, whereas on shallow soils, where this is not possible, an arborescent, though sometimes procumbent, trunk tends to develop.

The leaves of large macrozamias are often long and gently recurved, whereas in small species the fronds frequently are spirally twisted. Those of some species are grey-green; others are grass-green.

The cones of Macrozamia are stalked. Those of male plants are sometimes very numerous (up to 100) but commonly fewer than 10. In most cases the cones are produced at the top of the stem, as in other cycads, but those of several species are thought to be initiated laterally.

In some species the female cone remains closed until the seeds are shed; in others the seeds, which commonly are pink to orange-red, grow to such a size that the sporophylls shields are spread apart.

Microcycas has erect, occasionally branched trunks sometimes reaching 10 metres in height. When young, the stem is covered with old leaf bases and bands of persistent cataphylls, but eventually those are lost, and the trunks of older individuals are covered with a corky bark.

The leaves are numerous and in mature specimens are quite distinctive, accounting for the specific name calocoma, literally ‘beautiful hair’. The long, narrow, smooth-edged leaflets droop markedly from the rachis, and the terminal leaflets are virtually as long as the others, thus giving the impression that the end of each leaf has been chopped off. There is no series of reduced leaflets in the lower part of each leaf, so that the fronds, which are about a meter and a half long, have a rather sweeping appearance.

The cones of Microcycas are rather large. Both male and female sporophylls are covered with short wool. The overall appearance of the male and female cones is one of great geometric regularity, for the sporophylls fit very closely together and appear to be arranged in vertical rows.

In mature males of Microcycas, a new cone (sometimes 2 or 3) appears in early June, matures during July and August, and releases pollen in early September. The spent cone may persist several months. Female individuals also initiate a single cone in early June, but only in alternate years. The cone is pollinated in September and persists until the following June when the seeds ripen and drop from the cone.

The stems of Stangeria are completely subterranean and, because of this the leaf bases are deciduous, naked. The stems may attain a length of about 30 cm and a diameter of 15 – 20 cm, and quite frequently are branched. Stangeria leaves are once-pinnately compound, as are those of nearly all other cycads (two species of Bowenia being the sole exceptions), but are unique in their fernlike aspect, by contrast with the quite palmlike appearance of the foliage of other genera.

Alone among cycads, Stangeria does not produce its new leaves in an annual flush of several to many, but singly throughout the year. Only a few leaves, usually not more than four, are present at any one time, and these vary considerably in size and general appearance according to environmental conditions, occasionally approaching 2 metres in length. Longer leaves occur in populations growing in the shade of woodlands.

The cones of Stangeria are borne singly on comparatively long stalks (peduncles) holding the reproductive structures well clear of the stem apex, which is usually below the soil level. The cones are silver-grey and covered with a short velvety wool.

After Cycas, Zamia is the most wide-ranging cycad genus: although restricted to the Americas, it occurs from Florida and the Caribbean Islands, through Mexico and Central America, to South America, as far as Brazil, Chile and Bolivia.

The stems of many species of Zamia are quite variable. Although the stems of the majority are mainly or wholly subterranean, naked and often branched, and in some cases only a few centimetres long, (Z. pygmaea), the trunks of others can be above ground and fairly high. A few forms, particularly those from dense tropical forests in the south western part of the range, such as Z. poeppigiana, Z. obliqua, and Z. roezlii, have trunks several metres tall.
In general, the stems and roots of Zamia are much like those of other cycads, with extensive pith and cortex and sparse vascular tissue. Taproots, found in those species of Zamia having subterranean stems, may persist for many years, but trunking zamias often have extensive adventitious root systems, especially in such forms as Z. roezlii, in which the larger stems fall to earth, take root, and once again turn upward. The roots of all species form coralloid rootlets that contain cyanobacteria.

Zamia leaves, at least in general appearance, are likewise extremely variable. On the whole, the species with the larger stems also have larger leaves, but a wide range of leaflet shapes and sizes occurs. In some cases the leaflets are numerous and spaced regularly along the rachis in common cycadalean fashion (more than 70 pairs per leaf in Z. Chigua), but in others the pinnae are rather few in number and very broad.

The cones are very uniform throughout the genus, except in size. Both male and female cones are compact structures with hexagonal sporophyll ends (shields) that fit tightly together and appear to be arranged in vertical rows.

Female plants usually bear just one or two cones, and in nature these are not produced every year but on the average about every three years. Male plants produce cones pretty much on an annual basis and, unlike those cycads that bear one of two large male cones, many species of Zamia bear several to a dozen or more small cones.