Growing Ferns from Spores

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

Ferns are quite different from other plants in that they don't flower or produce seeds. Peter Bradley describes their life cycle and explains how to raise them from spores.

There are many ways to grow ferns from spores. Most methods require a little horticultural skill and a lot of patience but to understand the techniques involved it helps to know something of the fern's life cycle and of the sequence of events that occurs after spores are sown.

The seed of a flowering plant and the spores of a fern both serve two main purposes - reproduction of the plant and dispersal of the plant to new growing sites. The dispersal of seed occurs after fertilisation and the formation of an embryo, the dispersal of spores occurs much earlier in the life cycle of the plant, before fertilisation. In flowering plants the fertilisation of the egg to create an embryo follows pollination of flowers but in ferns fertilisation takes place after the germination of spores and will only take place if suitable conditions are created by nature or by the gardener.

Ferns are dependent on water to complete this vital stage in their life-cycle and on contact with a wet surface the spore will start to absorb moisture. The contents of the spore will then swell and burst through the outer wall. This growing tissue develops into a tiny, green, flat-growing structure called a prothallus which comes complete with male organs (antheridia) and female organs (archegonia) on the underside. The sperm released by the antheridia will swim to the archegonia to fertilise the egg cell (this is the equivalent of pollination and fertilisation in flowering plants). This procedure can only take place if there is a film of moisture for the sperm to swim through. The fern plant develops after this fertilisation and will draw nourishment from the prothallus until it is large enough to support itself, at which time the prothallus withers and dies.

This dependence on the continuous presence of water determines the special methods used by gardeners to grow ferns from spores and is one of the many reasons for the fern's abundant production of spores.

Compost and pots

A suitable compost on which to sow the spores consists of three parts moss peat and one part sharp sand by volume, finely sieved using a 1/8 in (3mm) mesh. This is then sterilised by heating to 180F (82C) for 30 minutes.

Clean and sterilise the required number of pots, 3in (7.5cm) clay or plastic pots are suitable, dry them well and loosely fill them to the brim with the sterilised compost. Firm gently to a level surface ½in (13mm) below the rim of the pot. Surface sterilise the pots and compost by applying boiling water from a metal watering can with a fine rose attached and immediately cover each pot with a square of clean glass, plastic or similar material and allow to cool and drain. This painstaking sterilisation is necessary to kill spores of mosses and liverworts which would otherwise smother the fern prothallia.

Sowing spores

Take the spores to be sown and dust a small quantity on to a clean sheet of paper about 6in (15cm) square. Tilt the paper from side to side and the spores will lodge on the surface fibres of the paper. Any excess can be returned to the packet. Remove the covering from a prepared pot and gently place the paper, spore side down, on the pot. Tap the paper and the spores should fall from the paper to the surface of the compost. Replace the cover and label the sowing. Do not cover the spores with compost.

Now make a stock solution of potassium permanganate (KMn04) by dissolving two tablespoons of potassium permanganate crystals in 1 pint (0.51) of distilled water and then make a working solution by diluting ¼ fluid ounce in 1 gallon (7ml in 4.5L) of distilled water. Stand the spore pots in a watertight tray and pour the solution into the tray to a depth of ½in (13mm) and keep it topped up to this level. The solution will be drawn up into the compost and deter algae and mosses which might otherwise contaminate the pots. Place the tray of pots in a warm, moist place in subdued light. Watering of the pots should not be necessary. A temperature of 70-80F (20-27C) is ideal and most gardeners keep the temperature at about 77F (25C) and reduce this as the plants develop.

If, in spite of all precautions, moulds develop on the prothallia, remove the infected tissue and at least ½in (13mm) of healthy tissue around it.

Germination may take from five to fifteen days but some species take far longer - even a year or more! The growing prothallia develop into a green mat and some gardeners transplant at this stage, lifting small clumps with tweezers and spacing them ½-1 inch (13-25mm) apart on a sterilised, finely sifted potting mix of peat and sand. The pot should still be covered to prevent the clumps from drying out.

If not overcrowded the prothallia may be left in their pots until the first fronds appear. Overcrowding prothallia of tree ferns such as Cyathea and Dicksonia species in particular produces poor spindly growth.

Once the young fern plants have appeared they may be transplanted so that development can continue. Small clumps are transferred three or four to a pot and placed on the greenhouse bench. At this stage begin to lessen the protection given by the glass or plastic covers. When the ferns are ½-1 inch (13-25mm) tall they can be individually potted into 3in (7.5cm) pots. Fully developed plants in 3in (7.5cm) pots intended for outdoors will still need considerable protection and should be gradually hardened off before planting out.

Spores which normally give quick and uniform results are those of Adiantum, Pteris and Pellaea species.

Collecting your own spores

Although a good range of spores is available through seed companies you may well like to collect spores from your own plants. At certain times of the year, the fronds may bear rusty coloured patches called sori on their undersides and these may be oblong, round or some other shape. These are clusters of spore cases. The sori may be covered by a piece of protective tissue called an indusium. This covering may be simply the edge of the frond rolled over to cover the sori, as in theAdliantum species. The shape of the sori, the type of indusium and its position are often important in identifying the different fern species.

It is essential to collect the spores at the right stage of development, ideally just before they are released naturally. When the spore cases begin to ripen they will turn from green to light brown, and then to a dark shiny brown or even black. (Some mature or ripe spore cases are yellow or orange.) The chances of success will be greatly improved by collecting spores from plants in vigorous growth.

Choose clean healthy fronds from which to collect spores and reduce the risk of contamination from other species by collecting on a cool or cloudy day. If necessary, the fronds may be carefully rinsed to remove alien spores and debris. Place each frond directly into a packet or envelope, alternatively lay the frond spore side down on a clean piece of paper and cover it to prevent the released spores from being blown away. After a few days in a warm dry atmosphere the spores should be released. Store them in packets or envelopes and label them with the name of the species, the source and the date collected.

Before sowing it will be necessary to remove as much non-spore material as possible to reduce the risk of contamination by algae, fungi and mosses. The spores, which look like very fine dust, will contain pieces of dried and shrivelled foliage, spore cases and other debris.

To remove this, empty the packet on to a clean sheet of paper, the larger pieces of non-spore material can then be removed with tweezers. Fine debris can be removed by slightly tilting the paper to one side and tapping the edge gently. The spores should remain in the middle and the non-spore material will bounce ahead from where it can be carefully brushed away. The cleaned spores can now be stored in a cool dry place until sown.

The sooner the spores are sown after collection the quicker the germination. Fresh spores usually have a high percentage germination, the longer they are stored, the slower the germination will be. The viability of some can be quite short, from a few days to a year, depending on the species.

If you are especially interested in ferns the British Pteridological Society, founded in 1891, provides a focus for fern enthusiasts through its publications and organises meetings, garden visits, plant exchanges and also has a spore exchange scheme.