Growing Alpines From Seed: Part 1

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

In the first of two articles Jack Elliott writes about successful methods of propagation of rock garden plants from seed.

Introduction

In no branch of gardening is seed-raising more important than in growing alpine plants. For the purposes of this article it is probably easiest to define 'alpines' as any plant suitable for a rock garden or alpine house, a broad definition which appeals to most enthusiasts as it covers all small hardy perennial plants, including bulbous and woodland plants, from true high alpines, which grow in areas with snow cover in winter, to bulbous plants growing around the Mediterranean.

We are therefore considering an enormous variety of plants, many of which are not readily obtainable from nurseries or even from fellow enthusiasts, but which can be obtained as seed from the lists of various international societies such as the Alpine Garden Society, the Scottish Rock Garden Club, the American Rock Garden Society and the Hardy Plant Society, as well as from various seed specialists advertising in the horticultural press.

In addition to giving an exciting choice of plants, growing from seed also provides sufficient stock for the grower to 'experiment with different planting positions and techniques. This can be invaluable when dealing with unfamiliar plants.

Germination factors

Successful germination of seed is dependent on several factors.

1. Moisture.

   The seed must take up water before germination can take place and subsequent drying out may induce further dormancy. It may be difficult to induce certain large, hard-coated seeds to take up sufficient water, hence the 'chitting' of peas, removing a small portion of the coat of each seed. This is certainly worthwhile for any hard seed which is large enough to handle in this way. Smaller, hard-coated seeds may be helped by soaking in water for twenty-four hours before sowing. Other methods of scarification, to damage the seed coat so that it lets in water, have been advocated, such as rubbing with very sharp sand.

2. Temperature.

   This is a vital factor and, although different plants may have different requirements, germination will only occur above a certain temperature, usually around 50F(10c). These two factors are largely responsible for ensuring that seed only germinates in the spring in mountain plants, which have a short growing period, shedding their seed shortly before frost and snow begins, after which the seed is kept cold and dry until spring. In the case of hardy lowland plants, for example under Mediterranean conditions, the dry summer prevents germination, which often then starts with the autumn rains if the temperature is sufficiently high.

3. Oxygen.

   Although this is essential it is unlikely to cause problems, except in unsuitable heavy, waterlogged composts lacking in drainage material.

4. Light.

   Although seed of some genera requires light for germination, in practice it seems unimportant with the method of seed sowing usually advocated. Even a surfacing of grit allows sufficient light to reach the seed.

5. Hormones.

   Seed germination is dependent on a balance between growth inhibitors and growth promoters, and it is through these that all the other factors probably operate. In practice, if the other necessary conditions listed are provided, the only hormone which needs to be considered is the growth inhibitor in certain seed coats, particularly the fleshy coverings of berries. Daphnes are a notorious example, but it is worth treating any fleshy covered seed to remove any trace of the original coat, by prolonged soaking in several changes of hot water, rubbing away as much coat as possible between each change of water, until the seed is clean.

6. Long Term Viability.

   Any gardener who experiments with seed of a large number of different genera will know that a considerable proportion fails to germinate in spite of the most careful attention to all these factors. Maybe this is sometimes due to a mysterious failure to overcome the hormone inhibitors, or other factors such as poor storage, but there seems little doubt that some seed is of short viability. This was discussed in more detail in a previous article (Seed to be sown fresh, Vol.2 No.3), but it is worth repeating that most Compositae and Ranunculaceae, and some Primula and Corydalis species, are notorious in this respect.

Seed storage

Most seed is obtained from outside sources and usually becomes available during the autumn, winter and early spring, so that the problem of storage does not arise. However, the collection of seed for your own use or for later distribution to others can start as early as May and continue until autumn, and this seed will need storing until it is distributed. If you are collecting seed for your own use, there is a lot to be said for sowing some of it immediately, especially with the genera of short viability, rather than waiting until autumn. It may not germinate immediately, but one often finds that eventually germination is better than with a late sowing. If seed is to be stored it should be kept cool and dry. Ideally, it should be cleaned and dried after collection and stored in a refrigerator (not a deepfreeze). One suspects that some of the failure of seed from seed lists of the Societies is due to the storage of seed in a hot office or a damp potting shed for several months!

Composts and Materials

For many years the standard compost for sowing any seeds has been John Innes Seed Compost, with a formula of 2 parts by volume of sterilised loam, 1 part moss peat, and 1 part sharp sand, with 1½ozs (43grms) superphosphate and ¾oz (22grms) ground chalk to each bushel (36 litres). The quality of John Innes composts is very dependent on the quality of the loam, and good top-spit, fibrous loam has become so hard to find that growers have increasingly been using soil-less composts, which are made up entirely of peat or a peat substitute and coarse sand, or grit of some sort, with essential nutrients added.

These seed composts generally are not ideal for alpine plants, but they are easily modified by the addition of extra drainage material. For a seed compost, as opposed to a potting compost, this must not be too coarse a grit, and either sharp sand or Perlite is more suitable. For this purpose the fine 'Seed Grain' Perlite is better than the standard grade. Depending on the amount of sand visible in the unmodified compost, which seems to vary from an adequate quantity to a total lack, up to a third of its bulk of drainage can be added. My own preference is for Perlite, a material which improves drainage greatly while retaining moisture. Its greatest advantage is that the texture of a compost containing a third of Perlite is such that the seedlings are much more easily separated from each other than in other composts, so that no roots are broken when they are pricked out. The addition of plenty of sand or Perlite seems to be even more important in many commercial Soil less seed composts, as the seedling roots quickly become intertwined and are almost impossible to disentangle in these without a lot of root damage.

For those who wish to make their own loam-based compost, a simple formula is sterile sieved loam 2 parts, peat 1 part, and Perlite (or coarse sand) 1½ parts, with superphosphate and chalk added as above, For ericaceous and other lime-hating plants, the chalk must be omitted am equal parts of peat, loam and Perlite can be used. Particularly for Ericaceae, even better results seem to be obtained by re placing some of the peat with sieved leaf mould, which should be sterilised separately by pouring boiling water through it.

The only other potting material needed is a suitable grit for surfacing the seed pans.

This surfacing is essential to prevent the seed being dislodged by heavy rain or watering, and also helps considerably in retaining moisture. Sources of grit vary across the country, but the most popular seems to be a small flint grit usually sold as 'chick grit' in various sizes. Other possibilities are small granite or limestone chip-pings (not for lime-haters), or aquarium gravel.

Pots

Plastic pots are generally unpopular with the experts for growing alpines, but this unpopularity applies mainly to the pots for growing mature plants of the more difficult species, which resent over-watering at any time. Certainly the compost in plastic pots retains moisture for much longer, and therefore, for many plants, better drainage is needed than in clay pots, but for young plants in small pots this retention of moisture is more of an advantage than a disadvantage, as the roots of a rapidly-growing seedling can cope with excessive water much more readily than those of a long-established plant.

One gets the impression that it is difficult to overwater seed pans or newly-germinated seedlings and is fatal to underwater them. It is therefore easier to use plastic pots, both for seed sowing and the first pricking out, unless the seedlings can be given constant attention in small clay pots.

Propagators, Frames etc.

Very few alpine plants need heat to ensure germination and the standard treatment should certainly be to keep them as cold as possible after autumn or winter sowing, keeping the pots outside in a shady place in all weathers. A few species will germinate more quickly with heat, and given a generous quantity of seed of an uncommon plant, it is always worth splitting it and starting some with bottom heat, or at least in a greenhouse, and some in the cold. This is the only possible justification for having an expensive electric propagator if only alpine plants are to be grown, but it may be ideal for starting greenhouse plants and vegetables.

One special piece of equipment which should be mentioned here is the Mist Propagator. Many amateur growers now have small units, incorporating bottom heat and automatic misting. Although not intended for seed-raising it can be useful for the few alpines known to germinate quickly with bottom heat, especially those with fine seed requiring the minimum of covering, which will be undisturbed by mist watering. Most units will keep the compost too wet and the seed pans will have to be covered with glass once they are soaked and the glass removed again when they begin to dry out.

Although it is best to keep the newly-sown seed pans under cold conditions, some sort of protection is invaluable for the subsequent care of germinated seedlings. For this purpose a frame is quite adequate, giving a little extra warmth for rapid growth, with protection from excessive rain. The lights can be taken off in good weather and replaced with some sort of shading during hot spells in summer. A cold greenhouse enables the grower to look after the seedlings in more comfort, but its advantages over a frame are more for the gardener than the plant! For alpine plants good ventilation is essential and, if this is lacking, then a frame is a much safer place for seedlings during warm weather, even with adequate shading.

The second half of this article will cover the practical aspects of seed sowing and the subsequent care of alpine seedlings.