Gentians

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

Gentians are amongst the most treasured of alpine plants. Jack Elliott explains how to raise the different types.

Gentians are perhaps the most popular of alpine plants, the plants that most alpine enthusiasts aspire to grow well. They fall very broadly into two groups conjuring up two very different pictures, one of sheets of electrifying blue in the high alpine pastures in early summer, the other of brilliant blue carpets in the autumn garden.

The spring-flowering gentians of the alps are Gentiana verna and its allies, which produce those wonderful patches of blue so difficult to emulate in the garden. It can be raised from seed and grown satisfactorily on a garden scale only with special care. The varieties of Gentiana acaulis with large trumpet flowers, are more easily raised.

Many of the commoner late summer and autumn flowering species are increased by division or cuttings, but there are still many which can be grown from seed, especially by the gardener with an acid soil.

Seed of many species of gentian can be obtained from commercial sources, and a wider range from such specialist Societies as the Royal Horticultural Society, the Alpine Garden Society, the Scottish Rock Garden Society and the American Rock Garden Society. If the seed can be collected from one's own plants, or from those of friends, it can be sown earlier in the summer or autumn than that from commercial sources, and this may influence the time before germination. Care must be taken in collecting seed to ensure that it is ripe. All the gentians have elongated capsules which gradually turn brown and eventually open at the apex to spill out the seed, which is usually very fine and brown in colour. The ideal time for collection is when the capsules first begin to open, or at least when they are becoming dry and somewhat shrivelled.

Seed sowing

Seed should, if possible, be sown immediately it is obtained. Viability varies from species to species and germination will probably be satisfactory even after storage, but nothing is lost by immediate sowing, and germination of fresh seed will almost certainly be more reliable.

A variety of composts can be used, the vital factor for raising alpine plants being that it should be well drained, so that an addition of coarse sand or fine-grade perlite will probably be needed to the available ready-mixed seed composts. For the spring-flowering or other lime-tolerant species, John Innes Seed Compost can be used but it varies considerably in quality and will need added drainage unless this is obviously adequate. A Soil-less seed compost is more suitable, again with the addition of a third of its bulk of coarse sand or perlite, and for the autumn flowering species it must be lime-free.

For those who make their own compost equal parts of sterile loam, sieved peat and seed grade perlite gives good results. To this mixture should be added superphosphate at 2oz to 8 gallons (60g to 40 litres) of compost with 2oz (60g) lime added only for the lime-tolerant species. The use of perlite seems to make it easier to separate the plants when pricking out, but the more orthodox coarse sand is also suitable.

Seed pans can be of clay or plastic, the latter preferable as the compost needs to be kept moist at all times. The size of pan depends on the quantity of seed, which should be sown quite thinly, so that the seedlings are not overcrowded by the time they are large enough to prick out. Gentian seed is very fine and needs the minimum of covering so the pot should be filled to within ½in (12mm) of the rim after pressing down and levelling, and the only covering for the seed should be at least 6mm of clean grit. Fine flint grit or small aquarium gravel is suitable. The grit serves two important functions: it retains moisture and it prevents any movement of the seed during overhead watering or heavy rain.

As a general rule the seed pots are best kept as cool as possible, and after sowing they should be put in a shady place with no protection overhead, so that they are rained on, snowed on, and frozen during the winter. The harder the weather the better the germination! Although this should be the treatment generally used, if sufficient seed is available, particularly of the later flowering species, and bottom heat can be provided, some seed can be sown in the same way but given bottom heat in a greenhouse. Under these circumstances a minimal covering of grit can be tried, either watering the pot from below by standing them in shallow water until the surface is wet, or using a fine mist spray. The only advantage of this method is that the seed may germinate within a few weeks of sowing, but with autumn sowing this means that the delicate seedlings will need looking after in a greenhouse during the winter.

With the normal cold treatment germination usually takes place in early spring, but if the seed cannot be sown until late then germination may be delayed for a year or more, and indeed seed pans should be kept for two or three years. There can be surprising delays! Ensure that the pans are kept watered at all times.

Pricking out

Once the seedlings appear they should be brought into more light, preferably in a cold greenhouse or frame, and pricked out as soon as they are large enough to handle, generally when two true leaves have been formed. Much depends on how crowded the seedlings are, hence the oft-repeated advice to sow thinly. If they are overcrowded then the sooner they are pricked out the better, whereas if they have been sown thinly they can be allowed to grow on for longer.

A suitable compost for the initial pricking out of the spring flowering species is John Innes No. 1. A Soil-less compost of similar fertiliser strength can also be used, but extra coarse grit or perlite, or a mixture of the two, should be added to make about a third of its bulk. If you use a compost containing perlite for the seed sowing, then a seedling compost of equal parts of loam and peat, with a further part of equal quantities of grit and perlite will give good results. To this is added 4oz of John Innes Base fertiliser to 8 gallons (125g to 36L) and for lime tolerant species only, 2oz (60g) of lime. For the lime-haters John Innes Compost is less suitable than soil-less compost or a fifty-fifty mixture as described.

If a source of acid leaf-mould can be found this is an ideal constituent of all the composts for this group, especially for pricking out and subsequent re-potting. A good formula is one part each of sterile loam, peat, and sterile leaf-mould, and one and a half parts of grit or perlite, with John Innes Base 4oz to 8 gallons (125g to 36L) for the initial pricking out and 8oz to 8 gallons (250g to 36L) subsequently. The leaf-mould must be sterilised separately, and this can be accomplished quite easily by pouring boiling water through it in a sieve.

The seedlings can be pricked out into individual small plastic or clay pots, or about 1in (2.5cm) apart into trays or seed pans. Most gentian seedlings are very small so that pricking out several into a container is probably more satisfactory. Once planted the seedlings should be kept slightly shaded and never allowed to dry out. Within a few months they will be large enough to plant in the garden or pot up separately, using a John Innes No. 2 Compost or similar, with added drainage, remembering that it must be lime-free for many species.

Although most species will make plants large enough for the garden or for their final containers within a year, time taken to flower varies from species to species. The majority should produce a few flowers in their second season of growth, but the large leaved summer-flowering species like Gentiana lutea will take several years to achieve flowering size.

Gentians in the garden

The large trumpet gentians of spring, the 'acaulis' group, which may be found in catalogues under the names G. acaulis, G. kochiana and G. dinarica, will grow in any well-drained soil in a sunny position. They fail to flower in some gardens:- a fruitful source of controversy among alpine enthusiasts! Enrich the soil with manure, plant extra firmly, and you should be rewarded with flowers!

The spring gentian, G. verna and its tricky allies G. brachyphylla and G. terglovensis, present different problems. If they grow well they will flower, but they require very well-drained almost scree conditions with up to 50% of grit incorporated in the soil, which must also contain plenty of humus, preferably leaf-mould. Growing in turf in their natural habitat, they seem to like company, so that pricking them out in two's and three's, and subsequently planting the seedlings quite closely gives better results than allowing generously for future growth.

Some of the summer and autumn flowering species will grow equally well in an alkaline or acid soil, especially if plenty of peat or leaf-mould is incorporated. G. lutea, with its splendid hosta-like leaves and 4ft (1.2m) spikes of yellow flowers, needs a sunny position at the back of the border, and will take two or three years to become established. G. purpurea and G. punctata are front of the border plants at 1-1 1/2ft (30-45cm), but the other tall European species G. asclepiadea, does best in more shady conditions with abundant humus. It is an easy long-lived perennial with up to 2ft (60m) high spikes of slender blue flowers, which will seed itself around when established.

The majority of the later flowering species are low growing plants suitable for the rock or peat garden, but can be established anywhere in partial shade if plenty of peat or acid leaf-mould is dug into the soil. Although many must have an acid soil two of the easiest G. septemfida and G. lago-dechiana, are less demanding in this respect and will also tolerate full sun if the site does not dry out. As with so many Asiatic plants, humus, moisture, and good drainage are the chief secrets of success.