GardenMessenger

This blog reviews the latest products, plants and innovations in gardening. It also provides a link for my many gardening friends who are members of the GardenMessenger and Seedmessenger Yahoo groups and their sub-groups that I moderate.

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Location: Australia

I am a semi-retired UK botanical garden curator and former international horticultural consultant, who has worked extensively in Europe, the Middle East, North America and Australia. I spend part of the year in Australia and part in Europe, mainly due to family and work commitments. I earn my living from writing and editing Internet copy, articles and books. I have written over fifty books on gardening and have been translated into twenty-four different languages. I am a former UK Garden Writer of the Year and a previous Quill & Trowel Award Winner from the Garden Writer’s Association of America. I am interested in developing gardening communities on the Internet and I manage the popular GardenMessenger Yahoo group, along with its various sub-groups like PondMessenger and SeedMessenger. I also edit International Water Gardener and its associated regional web-sites.

Friday, May 26, 2006

The "Missing Link"? Conifers from Seed and New Plants

Amborella trichopoda - The "Missing Link"?

Scientists believe that they may have found the "Missing Link" in the evolution of flowering plants. The results of a recently published study made at the University of Colorado, Boulder, in the United States involving a "living fossil plant" that has survived on Earth for 130 million years, suggests that its novel reproductive structure may be a "missing link" between flowering plants and their ancestors. The Amborella plant, Amborella trichopoda, which is only found in the rain forests of New Caledonia in the South Pacific, has a unique way of forming "eggs" that may represent a critical link between the angiosperms (or so-called flowering plants), and their as yet unidentified extinct ancestors. Angiosperms are thought to have diverged from gymnosperms (which comprise the conifers and cycads amongst garden plants) and the dominant land plants when dinosaurs reigned in the Cretaceous and Jurassic periods roughly 130 million years ago, and to have become the dominant plants on Earth today.

"One of the biggest challenges for evolutionary biologists is understanding how these flowering plants arose on Earth," said Prof. Friedman, of Colorado University’s ecology and evolutionary biology department, whose research has just been published. "The study shows that the structure that houses the "egg" in Amborella is different from every other flowering plant known, and may be the potential missing link between flowering plants and their progenitors. In basic terms, Amborella has one extra sterile cell that accompanies the egg cell in the female part of its reproductive apparatus known as the embryo sac". The discovery of the unique configuration of the egg apparatus, which is thought to be a relic of intense evolutionary activity in early angiosperm history, "is akin to finding a fossil amphibian with an extra leg," according Prof Friedman. "The unique four-celled egg apparatus in Amborella could represent a critical link between angiosperms and gymnosperms."

The origin and evolution of flowering plants has long confounded scientists. Nearly 130 years ago, Charles Darwin, known for developing the theory of natural selection, called the appearance of flowering plants "an abominable mystery." The surprising new finding suggests flowering plants may have arisen on Earth during a time when plant evolution was "particularly flexible." The peculiar egg-forming structure seen in Amborella may eventually link the odd South Pacific shrub to gymnosperms such as conifers, thinks Prof. Friedman. "We associate this structure with a relatively primitive reproductive process," he said. Amborella is a small shrub with tiny greenish-yellow flowers and red fruit that grows only in the understory of New Caledonia rain forests. The plants are unisexual, producing either all male or all female flowers, and so cross-pollination between plants is required for the single-seed fruits to be produced.

This is fascinating information for those gardeners with a broad interest in plants that goes beyond their cultivation and decorative or economic value. However, most will also want to know whether Amborella is easy to grow and if it has any decorative merit. According to early horticultural work with the plant by the University of California Santa Cruz Arboretum, once its requirements were understood it was not particularly tricky to grow, and they suggested as long ago as 1999 that they might undertake the propagation of Amborella as a novelty plant for hobby gardeners. As far as I can discover this has not happened to any great extent and it has not become available in the horticultural trade. Clearly it is not a high flying ornamental. Unlike the living fossil, Metasequoia glyptostroboides, which was the focus of similar attention in the 1940s and has gone on to become a most valuable deciduous conifers for garden and landscape.

Conifers can be easily seed raised

It was originally conifers that I was going to write about today before being distracted by the Amborella story. This was following a note received from Mark in Bendigo, Victoria, Australia, about the best way to raise conifers from seed. Of course it is presently the season in Australia when cones are freely available on mature coniferous trees and are full of ripe seeds, although seeds of many of the most popular conifers for the garden are now widely available from seed suppliers. Irrespective of their source or where you live in the temperate world it is still an opportune time to sow seeds of conifers.

Although growing conifers from seed may seem a very long-term project, and in many cases the gardener who sows the seed is unlikely to see the mature tree in all its glory, this is nevertheless a viable and very exciting enterprise. Most conifers are easy to germinate, and amongst the most popular kinds are a number that will attain a respectable size within two or three years. Certainly of a stature that will give even the most impatient gardener the feeling that raising conifers from seed is a viable prospect. There are many kinds of conifer seeds but most are of a conventional nature and easy to handle. It is only a few like Araucaria - the Monkey Puzzle and Bunya Pine - that create any difficulty. These are oily seeds that must not be allowed to dry out if they are to retain their viability. Indeed, they often start to germinate immediately they fall from the tree, tiny embryo roots starting to emerge within a matter of days. Clearly for the best results, immediate sowing is essential.

Sow Araucaria seed directly from the cone

The more usual pine and cypress seeds are sown in a similar manner to many other garden seeds, usually being stored until the spring before sowing in order to benefit from a full growing season, although in practice they can be started at most times of the year. Although it is easier to control seedlings that are raised in pots, it is quite common to sow these directly into the open ground in a well prepared nursery bed, or else a special bed created in a cold frame. While frame protection is not necessary for cold weather, except with a few sub-tropical species, it is much easier to protect the seeds and emerging seedlings from birds and vermin in a frame structure if this is carefully netted. If pots or seed trays are used, then any compost that is suitable for seed sowing can be employed. Each kind has its advantages and disadvantages. Soil-less compost offers a perfect structural medium for maximum germination, although because of its friable nature it is often not harsh and coarse enough to remove the seed coats from emerging seedlings. Hand removal often causes damage and leaves the green tissue open to infection. Non-removal will generally lead to the demise of the seedling.

Soil-based seed composts do not always produce the same germination results as soil-less composts. However, they are usually sufficiently harsh and abrasive to remove the seed coats from seedlings as they push up towards the light. Being soil-based such composts are mostly colder, and seed germination is rarely as rapid as when a soil-less medium is used. On the other hand seedlings produced in a compost composed mostly of soil are generally much hardier and easier to handle and transplant than their soil-less raised counterparts. Both are sterilized mediums, and while this means that attacks by soil-borne pathogens are minimised and weed seeds are eliminated, it also means that the fungal associations that conifers enjoy with soil dwelling micro-organisms are unavailable, and seedling development is inhibited compared with seedlings that are raised in natural soil, especially soil where conifers have been growing previously.

It is the knowledge that conifers benefit from this association with soil-borne fungi or mychorriza that has given rise to the invention of the Dunneman Seed Bed. This is a seed bed that incorporates conifer needles and similar "forest floor" debris which is then used as a seed germination and growing on medium. Gardeners have taken this foresters’ technique for seed raising and adapted it to their own circumstances. The best way to do this is to inoculate a soil-based compost with a mixture of soil and debris from beneath a garden conifer. Mix up to half and half by volume to create an excellent seed sowing medium. This can be made into a small nursery bed in a frame, or else seeds can be sown directly into pots or trays filled with the mixture.

Conifers have an association with soil-borne fungi

Sow seeds sparingly and cover them by about their own depth with compost. All the popular garden conifer species are best germinated in cool conditions, a temperature of 7.5 -12.5ºC (45-55ºF) being perfectly adequate. The growing medium should be kept moist, but not wet. There is great variation with the period of time during which conifers will germinate. Some will emerge within a week or ten days while others make take several months. Not all will germinate uniformly, so if only a handful of seedlings appear, once they are transplanted, retain the pan or flat of compost for several months before discarding the contents as further seedlings may appear.Conifer seedlings should be transplanted as soon as they are large enough to handle. Plant in individual pots or modules so that they can develop a strong fibrous root-ball. Pot grown conifer seedlings are much easier to transplant and establish then those that are lifted bare-rooted from nursery rows.

News

Chrysanthemum ‘Osorno’
This recently introduced Chrysanthemum is the toast of the Dutch cut flower trade, already in the few months since its introduction having sold over 1 million cut stems. Now it is being considered as a prospect for the hobby gardener. Of course it may behave differently in the home garden where it will lack the sophisticated environment of the commercial cut flower grower, but the chances are that it will make a most useful addition to the green flowers that are currently available to floral art enthusiasts. ‘Osorno’ has a fairly flat flower head and medium-sized dark green leaves. It also has a strong natural resistance to disease. The name Osorno is derived from the volcano of the same name in Chile. Keep a look out for this cultivar appearing in nurseries shortly.

Nepenthes ‘Rebecca’
This is a cultivar that has been developed for the house plant trade. For the first time gardeners can buy a Nepenthes that is of neat, compact and even habit. Its pendulous pitchers are dark purple, and the foliage dark green with a deep red haze.








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Philip

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Photos:
Amborella: University of Colorado
Conifers: Wikipedia
Chrysanthemum and Nepenthes: Flower Council Holland

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