Natures plan has been to use insects or the wind to breed flowering plants. Food and drink in the form of pollen and nectar induce insects to do the work. Even though bees do not know what they are doing, the job its done.
A new element now enters Nature’s plan – intelligence on the part of the breeder or pollinating agent. This began at the time of the Romans, or even earlier among the Chinese, when someone found that shaking the pollen if a flower upon the open face of another would produce seed-yielding plants that bore flowers different from either parent. Man with his intelligence, is Nature’s way of staying one step ahead of the bee.
The Great Architect has a simple plan upon which the flower is built. The drawings aim to show this. Although Nature plays the tune with many variations, the theme is the same. There is the stamen with its pollen-hearing anther (male) and the bottle-shaped pistil (female) which holds the ovules or egg cells – the seed-that-is-to be. The stigma, at the top of the pistil, has a sticky receiving surface where the pollen grains are deposited by wind, insects or man and sprout awl grow into pollen threads or tubes. These tubes grow through the neck of the bottle, called the style, into the ovary.
The male reproductive cell is formed at the end of the pollen tube. One male cell fuses with an egg cell and from this union the seed, which contains the embryo develops.
In the flower, the pistil may be single or compound. Stamens and pistils are usually found in the same flower on most kinds of plants but they may be in different flowers on the same plant, as in corn, or on two different plants, as in holly which has male and female plants.
Your job, as breeder, is to select the parents and bring the pollen of one to the stigma of the other.
In the image below, the flowers are arranged in order from the simpler to the more complex – the lilies to the composites. The gladiolus is out of place; it belongs to the iris family. Like the iris, it has three stamens and three stigmas. This order of arrangement is the same as that in which flowering plants appeared on the earth. This is indicated by the fact that, as yet, no fossil composites have been found – roses, yes, but no composites.
The composites – dahlias and chrysanthemums, for example, among garden flowers – are Nature’s most recent achievement. Wild forms have conquered the world – note the dandelion. Each seed is separate and is provided with a means for wind dispersal.
The small size of the pistils stamens in the composites present real difficulty to the breeder. Some resort to segregation of parents allowing insects to do the work, others use a lens.
The thrilling adventure of producing something new and better is always the breeder. More and more amateurs are finding this out. The necessary knowledge is widely available.
Gladiolus, iris or daylilies are suggested as places to start. The stamens and pistils are large, the pollen is plentiful, the seedlings are easily grown and they bloom the second year. It is foolish to start with daffodils or orchids which take five to seven years to bloom.
The unfurling of the flower petals is the invitation to the bee and the signal that the flower is ready for pollination. To prevent chance pollination by insects, the bud may be bagged in waxed paper just before opening.
When the petals are large, they may be cut off at the base as the flower begins to open but care should be taken to and avoid injuring the stamens and pistils. When the petals have been removed there is little left to attract insects and their foothold is gone. The pollen parent may be cut to open indoors. Cut the stalk just before the blooms start to open. In this way contamination with offered foreign pollen is prevented and there will be more pollen with which to work.
The stigma is receptive when a sticky secretion appears on its surface. This is the time to pollinate. Since the pollen holds its life a long time, it is good to pollinate as soon as the flower opens; the pollen will then be there when the stigma becomes receptive. Dust the pollen on gently to prevent injury. Repeated pollinations on successive days with pollen of the same cross helps to insure success.
Avoid self-pollination by “emasculating” the flower of the seed parent – this means removing the stamens. Do this before the anthers open, however, for otherwise the pollen may fall or blow upon the stigma as you handle the stamens.
Most flowers have plentiful supplies of pollen but sometimes it is not easy to find. Slitting the anthers in iris sometimes reveals unsuspected pollen. The anthers of the African violet must be cut open with a razor blade to obtain the pollen. Highly bred varieties may have no pollen and only the disk flowers in chrysanthemums and dahlias carry pollen. When working with these, watch the bloom as it matures and collect the pollen as it appears. Pollen may be stored in the refrigerator between waxed paper at 40 to 50 degrees.
The temperature and time of day are important when pollinating but this varies with the flower. For glads. it is said, before 9 A.M. and after 6 P.M. on a sunny day is best. The time is unimportant with iris so long as the day is fair and still. With chrysanthemums, a warm, sunny day is needed. Camellias are said to need 65 to 70 degrees for the pollination to take.
What is a Good Cross?
Experience, alone gives the answer to this question. Some varieties will always make better parents than others: some will be found sterile, and some crosses will not take.
Camel hair brushes were once thought best for transferring pollen but they must be dipped in alcohol between different crosses and the alcohol is slow to evaporate from the inside of the brush. Fingers may be used but locking forceps work much better and their use prevents contamination from soiled fingers. My favorite tool is a locking hemostat, a surgical instrument somewhat like scissors but without cutting edges and with blunt tips. When the stamen is seized between the tips the handle can he locked.
Binocular lenses are excellent when working with small flowers. Mounted and worn like eyeglasses, they leave the hands free. Brightly colored small labels, upon which to write the time, date and name of seed and pollen parent are important, as is a notebook to enter the crosses as they are made. Also helpful are glass vials in which to transport pollen with labels.
Label The Cross
Experienced breeders will be more apt to tell than to listen when it comes to such matters as technique but the beginner will want to profit by the experiences of others. Label each cross with a tag on the stem, placing the name of the seed parent first – Snow Flurry x Snow Carnival, meaning that the iris Snow Flurry is the seed parent and Snow Carnival the pollen parent.
It is common sense to know the culture of the plant before starting to breed it. Control of diseases and pests ought to be understood, otherwise the time given to breeding is apt to be wasted. The virus diseases are especially important. Although the seeds, themselves, do not carry the virus, the seedlings may become infected. Daylilies seem to be the only group free from diseases and pests and owe much of their popularity to this factor.
Breeding for disease resistance is a profitable field, in many cases much more profitable than breeding for form or color. However, the problem is mostly beyond the amateur, although he should be aware of its importance. Destroy all but healthy stock to reduce prevalence of disease.
Although the great majority of seed germinates a few weeks after planting, an after-ripening period is needed by some. This is the time between the ripening of the seed and the time it starts to sprout or germinate. In the holly, for instance, the seed is ripe in November but will not germinate until two winters have passed over it. Other seeds require an after-ripening period of from six months to a year. The table on page 50, gives the after-ripening time of some common garden plants.
In general, growing plants from seed depends upon keeping the seed free of fungi and insects and preventing the soil from infecting the seedlings. Use of sterilized soil may also be helpful.
What Plants To Cross?
What plants to cross is always a question. Crosses between families or genera are impossible for they are too unlike. Crosses within the same species are apt to be successful, as are crosses between two species when they have the same chromosome number. Inter-species crosses, those made between different forms or varieties of the same species, are likely to take. The beginner should confine himself to such crosses.
Plant breeders work in different ways. Some will cross every which way with no planned results; they will be grateful if something good appears. Others plan crosses carefully. They will dream up an ideal variety and then plan the parentage to bring it to a reality.
Inter-species crosses, those between different species, yield hybrids. Some hybrids may start a whole new line of plants if they prove fertile, i.e., able to reproduce themselves. This is a field for the experienced breeder.
The personality of the breeder often shows itself in the selection of varieties he crosses. Good advice to the beginner, however, is to breed from the best and breed close. For instance, to produce a good white mum, cross two of the best whites that are most nearly alike.
What varieties you choose to keep or discard depends upon the dream you have and what you are working for. A tip to the wise – discard inferior seedlings while they are in bloom. Always recognize the value of previous selection.
Scientific plant breeding has a brief history. Sex in plants was a debatable question 250 years ago. Less than 150 years ago, in 1866, Gregor Mendel discovered unit characters. Since then, chromosomes and genes, as the units of inheritance, have given rise to the science of genetics and have made possible great advances in breeding.
Although much has been done without benefit of such knowledge, with it failures can be avoided and success predicted. Chromosomes are the bearers of inherited characters in sex and body cells of all plants and animals. They are microscopic and constant in number in each cell within a species. They are constructed of smaller units, genes, which carry the unit characters. Once in every generation the chromosomes are re-assorted and new individuals thereby produced.
In iris, the “diploid” bearded iris have 24 chromosomes; I. pumila has 32; some dwarf forms 40, and the tall bearded 44. The chrysanthemum, also, is a “polyploid” genus with the basic number nine, though species with nine chromsomes are not known. Diploids with 18 are numerous; the arctic daisy has 90; and the garden chrysanthemums, C. sibiricum (Korean hybrids) and C. modfolium have 54. Species which have the same number of chromosomes are more apt to cross successfully. Species crosses where the counts are different are more difficult though, in many cases, possible.
Some unit characters, as they are carried from generation to generation, exert dominance. To get a good red in-curved pompon, the chrysanthemum Grenadier, a red reflex pompon. was crossed with a buff incurved pompon. All the seedlings were predominantly red and also reflexed. In a few days, however, all the blooms turned an unattractive brown, a character also inherited from Grenadier. This, and the reflexness are examples of unwanted dominance.
The plicata character in iris is recessive. Recessiveness is opposite to dominance, the character appearing to be lost although it is not. In breeding for this character, it should be present in both parents. If present in one, it may be brought out in crossing back on the plicata parent. In a cross with Blue Shimmer, a plicata, and Great Lakes, none of the first generation were plicatas. Back crossing on Blue Shimmer gave an expectancy of one in nine. I got two plicatas from the total of 18 seedlings which I grew.
Breeding from the best varieties worked well with me. Crossing the two best white iris at the time, Snow Murry and Snow Carnival, gave me Two Snows, a ruffled, flaring white with fine substance.
Making pedigree charts, using color to show the inheritance of color, is good winter work. The iris check list, for example, makes it possible to search into the parentage of many varieties before an attempt is made to breed them.
Other than by sexual reproduction, new varieties appear from time to time as sports or mutations. Many of these turn out to be sterile so Nature has no use for them but they are useful in the garden. The camellia Herme has given 17 sports, many of which have been introduced as new varieties. Our Herme has sported to Pink Herme but the parent is a better camellia. The chrysanthemum Valencia has given numerous sports and there are three popular ones of Indianapolis. Everyone should be on the lookout for a new form or color on an old variety. Since there is no control over the origin or nature of sports, cross breeding alone offers the only method of control and, hence, a more practical and interesting way of getting new varieties.
Whoever plans to enter the field of amateur breeding should at once join the society devoted to the flower of his choice. There is a society for almost every flower.
by J McKane
