Cycads: Living Fossils

Table of Contents and IntroductionAfrican Violets: the Doyen of House PlantsAgapanthusAlstroemeriasAmerican SagebrushesAmerican WildflowersAndean Nymph - a pink mimulusAquilegias (Columbines)AuriculasAustralian AnnualsBellis Perennis (Daisies)Black-Eyed SusanBlue African LiliesBreeding DelphiniumsBreeding Fuchsias: Part 1: From SeedBreeding Fuchsias: Part 2: HybridisationBromeliads from SeedButterflies in Soy SauceCacti RaisingCampanulasChilean Bell FlowerChilly Treatment for Peruvian LiliesCollecting SeedConserving Annuals and BiennialsCosmosCucumbersCycads: Living FossilsCyclamen for IndoorsDahlias from SeedDamping OffErythroniumsF1 Hybrid - What Is it?F2 and Open Pollinated VarietiesFrom Obscurity to the Height of FashionGentiansGeraniumsGermination to Pricking OutGolden Impatiens - The StoryGrowing Alpines From Seed: Part 1Growing Alpines From Seed: Part 2Growing Bananas From SeedGrowing Cyclamen From SeedGrowing Eucalyptus From SeedGrowing Ferns from SporesGrowing Foxgloves From SeedGrowing Fritillarias From SeedGrowing From Seed: From Packet to SoilGrowing Hardy Ferns from SporesGrowing Hardy Geraniums From SeedGrowing Lewisias From SeedGrowing Magnolias From SeedGrowing Meconopsis From SeedGrowing Proteas and Related Genera from SeedHandling Small SeedsHardy Annuals: Part 1Hardy Annuals: Part 2Hardy CyclamenHardy SpurgesHelleboresIncreasing your Violas and ViolettasKeeping Records of Seed SowingLettuce - the Vital Part of any SaladLord Anson's PeaMagnolias - the Root of the ProblemMimulus from Seed to Seed in Sixty DaysNew Guinea ImpatiensOld-fashioned Sweet PeasOnions with EverythingPansies are not Difficult to Grow from SeedParsleyPerennials for American GardensPetuniasPhygelius - their cultivation and propagationPinks: Evocation of the PastPlants That Flower OncePrickly but NicePropagatorsRadishesRaising PalmsRaising PrimulasSalad Leaves - a lot to be desiredShow Stoppers Twice OverSowing SeedsSowing in Open GroundSowing to Feed our FriendsSturt's Desert PeaSweet Peas - Autumn SownSweet Peas - Sowing and GerminatingTall and HandsomeTechniques with Tiny SeedTexas BluebellThe Effect of Light on Germination and SeedlingsThe Nervous PeaThe Scarlet Welsh PoppyThe Search for the Yellow Sweet PeaToad LiliesTomatoesTreasure Hunt for TasteUnderstanding Latin NamesUnique Poppy (Mother of Pearl)Viability of VegetablesWeaning SeedlingsWill the Real Mimosa Please Stand Up

Tony King has a passion for cycads and here he describes these long-lived plants.

Often referred to as living fossils, cycads are truly descended from an ancient lineage. It would be wrong however to assume that the species in existence today are totally unchanged from their ancestors which dominated the world at the time of the dinosaurs. True, the plants exhibit many characteristics thought primitive by plant taxonomists but none the less, marked adaptations to harsh environments are often encountered. Such conditions are far removed from the stable, warm, humid climate that prevailed during the cycad heyday millions of years ago.

Distributed in the Americas, Africa, Asia and Australasia, the surviving species are but a remnant of those that once inhabited our planet. In the wild they face mounting pressure from habitat destruction and human exploitation which, when coupled with their slow rate of development render natural recovery almost impossible. All cycads enjoy protection under CITES which may be further backed in their homelands by stringent protective legislation, such as in South Africa. Many countries however are slow to recognise and effectively safeguard their native cycad species. Cultivation and seed production in gardens such as Fairchild in Miami, Florida, the holder of one of the world's largest cycad collections, may offer hope for the survival of many species such as the very rare Microcycas calocoma from Cuba.

The majority of cycads are evergreen and generally resemble palms in appearance. They possess a large, bulky tap root and also produce special 'coralloid' roots, which grow upwards to the soil surface. These are home to algae which benefit the cycad by producing nitrogen to assist the plants growth. In cultivation these should never be removed. Species vary in height from those with underground stems to those which may tower to 20m (65ft).

Growth occurs in cycles from a terminal bud at which time many new fronds may be produced and the stem increases quite considerably in both height and girth. These flushes of growth may occur annually but it is not unusual for plants to miss several years, saving energy only to produce a bumper crop of new foliage. Upon emergence, the leaves are tightly curled and very delicate. They rapidly expand outwards, unfurling to reach their full magnificence, setting hard, almost like plastic.

Growth is slow and plants live to a great age, indeed the oldest pot plant at Kew is a South African cycad over 200 years old and still going strong.

Propagation

Maturity is normally attained after many years of growth and sees the production of the organs of reproduction, the cones. Each plant will be strictly either male or female and the number of cones produced varies from one per plant upwards. Generally males carry the most but female cones tend to be much larger.

Coning is frequently triggered by the changing seasonal weather patterns, e.g. after the rainy season. It was long thought that the wind was the major agent responsible for the transfer of pollen between plants. Modem research is however discovering that insects play the major role in effecting pollination. Some of these plant/insect relationships are very specific, each partner dependent upon each other for reproduction.

Upon pollination, the slow process of seed maturity commences which often takes a full year. In the case of some genera, notably Encephalartos from Africa, the kernels develop to full size whether or not fertilisation has taken place. Being infertile, such 'seeds' will fail to germinate. Unlike other plant groups, cycad seeds do not undergo a period of dormancy. Instead they slowly mature by a process which may continue after they have been shed from the disintegrating female cone. The seeds themselves are extremely toxic as indeed are all parts of the plants.

The seed ripening behaviour of cycads gives rise to a classic method to determine viability - the float test. In this, seed is placed in a bowl of water. Old or infertile seed (except Encephalartos), will float and should thus be discarded. Mature, heavier seed will sink. Remember, Encephalartos seed, if fresh, will sink even if it is infertile. Any seed that passes the test should be sown, but any that remain un-germinated after three months should have the test repeated. If they sink re-sow but if they were infertile the kernel will have shrunk in size and the seed will float and can be discarded. Just to complicate matters a few species such as Cycas rumphii have seed designed to float so the test cannot be applied to these, though such species are few in number.

I sow my seed as soon as received into a seed tray filled with a free-draining soil-less compost and grit. The seeds are pressed into the surface, half buried and laid upon their sides. A fungicide solution like Cheshunt compound is recommended to water them in since in my experience moulds readily set in. Placed into a propagator at a temperature of between 75-80F (24-27C) and germination will be erratic taking from a few days to well over a year depending on the age of the seed when you received it. Germination will be readily apparent since a green structure will begin to emerge from the seed and grow down into the compost. At this stage, carefully transplant the seedling into a container with sufficient depth to accommodate the large tap root that will soon develop, keeping the seed at the surface. 3½in (9cm) pots that are 5in (13cm) deep are ideal. I prefer a compost mixture of 40% John Innes No. 2, 40% cocoa peat and 20% grit. It is vitally important to ensure that drainage is excellent as the root system is prone to rotting.

Kept in a warm, moist environment with light shade you will soon notice the development of a swollen crown at the soil surface. From this the first leaf will emerge and rapidly expand. It is essential that during these early stages seedlings do not dry out which can prove fatal. For the next few years, during the juvenile period, leaves tend to be produced sporadically but should increase in size on each occasion.

Cultivation

Subsequent cultivation for the majority of species is trouble free, with water being supplied liberally during the warmer months, much less during winter when the soil should be kept just moist. I apply a general liquid feed every two weeks during the summer and this is especially beneficial when new growth is being produced.

A winter temperature of 50F (10C) is recommended though temperate species such as Cycas revoluta will be happy at lower temperatures if kept drier at the roots. Generally trouble free the main pests to look out for are mealy bug and scale. Normal chemical control can be applied. The tough foliage is not troubled by aphids.

As the seedlings develop they will adopt the typical cycad growth cycles, producing flushes of leaves. Surprisingly, under cultivated conditions rates of growth can dramatically increase and impressive sized plants can be obtained relatively quickly.

Plants for Beginners

The following can be recommended as ideal beginners plants, kept free from frost in winter: