Golden Impatiens - The Story

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

Plant breeders are increasingly looking to wild species to help create new varieties. Last year saw an expedition to south east Asia in search of an impatiens to bring a new colour to garden and greenhouse varieties. Keith Sangster tells the story.

Things have changed in the plant breeding world. In the past many new varieties were raised by private individuals, or their head gardeners, and their spread throughout the gardening community was relatively slow. But now plant breeding is a more competitive business with large companies operating in America, Japan, Holland and Italy, as well as the UK and other countries, and distributing their varieties all over the world.

Few of the seed companies that sell seed to amateur gardeners do a great deal of plant breeding, as it is usually more economic to buy varieties from specialists. However where we see an opportunity to introduce something special we like to do so if we can.

In the last fifteen years the humble busy lizzie, Impatiens, has made the transition from a rather leggy house plant to one of the best of all summer bedders for cooler sites and soils which don't dry out. Altogether there are between five and six hundred species, growing mainly in the mountains of Africa and Asia with few in Europe, but just two types have been responsible for the upsurge in popularity. Most of the bedding types have been developed from I. wallenana, a perennial from Zanzibar which in its wild home grows to about 2ft (60cm) and has scarlet flowers 1½in (4cm) across. It is obvious how much this species has been improved. Even so the colour range remains restricted to reds, pinks, lilacs and white with green foliage.

Less common are the varieties from New Guinea. These need warmer temperatures and a more humid atmosphere in cultivation. But they are almost all raised from cuttings as the problem of producing good seed raised varieties has not yet been solved. But they have the great advantage of foliage that comes in a variety of shades including shining purple and various yellow and cream variegations. The flowers are larger and include a good orange. Apart from a strong blue, the only colour missing is yellow.

Dr. Rob Oliver, an Australian botanist, felt that a wild species with yellow flowers growing in Malaysia, Impatiens oncidioides, could provide the genetic material to bring yellow flowers into the New Guinea impatiens and approached us with a suggestion that we sponsor an expedition to collect seed. This could then be used in hybridisation. After careful consideration of both the problems and advantages of using this species in plant breeding we decided to agree to support the expedition and authorised Dr. Oliver to go ahead with obtaining the necessary permission and other documentation.

The expedition

The plant grows in the Cameron Highlands in Peninsular Malaysia and I will now let Rob Oliver take up the story.

We arrived in the Cameron Highlands during the only rain of our stay. The rest of our stay was, weather wise, close to paradise. On immediate inspection we found the plants in flower but very few seed capsules in evidence. The first three days we spent spinning out trying to find enough. By the seventh day we had a small amount of seed and then followed up leads supplied by locals and ended up going well into the forest to a village on the edge of an old tea plantation. We had been told that the plant was a weed there but they turned out to be I. walleriana growing in great profusion.

We eventually found the first reasonable amount of plants in a gully at 5,000ft and then found a great deal more plants at 6,400ft.

A lot of our work was done standing in streams as the vegetation is so dense and it was easier to walk in the water. There were also a lot of the very sharp leaves of the screw pine, Pandanus, which also made walking very difficult.

A problem then arose in that although there were literally millions of plants only about 1 in 100 were in flower and these flowers were producing little seed. There was also a lot of insect damage to the plants. Kathy (Dr. Oliver's wife) noticed a large black swallow tail butterfly called a Red Helen pollinating the flowers, inserting its proboscis into the long nectaries. Ironically most of the damage to the plants was being done by caterpillars of this butterfly.

We decided at this point to spend an extra week in the mountains and also to engage the services of a local that we knew. The plan was to hand pollinate as many flowers as possible and teach our helper, Rajan, to pollinate, collect and dispatch the seed. Rajan is an intelligent and reliable person who we felt sure would follow our instructions carefully.

Bringing seed home

When seed was ripe a supply was collected, being careful to leave more seed on the plants than would have been provided by the inefficient pollination of the butterfly. Rajan was left behind to repeat the pollination and collection procedure.

When the Olivers arrived back in Australia they encountered a problem. In spite of having all the correct documentation, the customs insisted on impounding the seed and treating it with a fungicide as a precaution against the disease. Unfortunately impatiens seed will not tolerate this treatment and the seed was killed. After representation to the appropriate authorities the consignment sent by Rajan was not treated and came through customs safely.

Such was the success of the hand pollination that seed is available in sufficient quantities not only for the plant breeding programme but to offer to customers. The plant is not a showy one and it is difficult to grow but is a fascinating plant for enthusiasts.

Growing the Golden Impatiens

The seed should be surface sown on a Soil-less seed compost containing sand like J. Arthur Bowers Seed and Potting Compost. Once sown do not cover the seed with compost but enclose the pot in a polythene bag after sowing and seal it with an elastic band. Germination can take from 4 to 21 days at 70-80F (21-27C). Aim to keep the compost a little more moist than usual though not overwet.

The key to growing Impatiens oncidioides is to provide a stable environment. This environment is made up of several factors, the most important of which is humidity, atmospheric humidity should be no lower than 70%.

When pricking out the seedlings it pays not to use a standard compost as a proprietary orchid compost is more suitable. If you prefer to make it yourself a mixture of five parts crushed bark to one of sharp sand is ideal; if possible the bark should be less than 3/8in (1cm) in size. As a last resort use coarse grade moss peat. Remember that growing conditions will be very wet but the compost must not be allowed to become waterlogged.

To help maintain a high humidity grow the plants on capillary matting or stand the pots on trays of gravel or pebbles which are kept constantly moist. A sign of good growing conditions is the growth of roots from the lower stems just above the compost. A sign of insufficient humidity is the dropping of healthy leaves. In its natural home this plant grows best with its roots in running water and the tops of the plants protruding into the rather brighter light above the streamside vegetation.

The plants are not fussy about light intensity as long as the moisture level is high and they will tolerate a wide range of temperatures from 43-86F (6-30C) although they prefer to be kept relatively cool in the winter.

The plants appreciate regular feeding and a liquid feed containing trace elements, such as Maxicrop, should be applied every week during the growing season.

Breeding work

The results from the first stage of the breeding work are a little mixed. Plants grown from seed collected in the wild and then self pollinated have produced good quality seed and lots of it so we should be able to supply future seed for the catalogue from cultivated plants. There are many plants now growing and the tallest is 2ft (60cm) and covered in scores of flowers. The plants are tall and come late, they have many branches and are extremely vigorous.

Crosses have been made with a number of New Guinea types and when the resulting seed was grown on and flowered we were surprised to find that all the plants had lilac flowers! We are now conducting more crosses.

Now available from Thompson & Morgan is the improved Impatiens Jungle Gold.