Hybridizing or crossing plants to improve them is a fascinating experience that any home gardener may enjoy. The minimum requirements for hybridizing are a love of plants, a little space, and enthusiasm.
Hybridizing is easy—producing a plant of outstanding merit is difficult. This is the reason for the requirement for enthusiasm.
However, the possibility that something extraordinary may turn up keeps hybridizers, amateurs, and professionals going.
The similarity between hybridizing and horse racing is closer than you think!
Genetics: The Science And Art Of Plant Breeding
Genetics has made plant breeding a science as well as an art. It has eliminated some of the guesswork and has increased efficiency.
Plant breeding, however, still remains very much of an art. The primary requirement of a plant breeder is to be keen enough to know a good thing when he sees it.
This is something you do not learn by reading books (or articles on hybridization).
Choose Your Plant
The way to learn to swim is to swim. Knowledge of the physics of swimming is not a necessary prerequisite.
It is reassuring to know, however, that a body will float. Once you have managed to keep on top of the water more often than under, the science of swimming becomes a necessity if you do not want to merely flounder.
The same holds for plant breeding. But first things first—so let’s jump right into it.
First, what plant should a beginning hybridizer choose for his pursuit?
There are numerous possibilities. Here are a few suggestions.
If the primary requisite for a hybridizer is enthusiasm, the second is to know your plant.
Select one that you can grow. If you cannot grow strawberries—do not try to be a strawberry breeder.
If you can grow gladiolus and like them, why not try hybridizing them.
Unless you are ambitious, choose a plant that can be propagated asexually—that is, a plant that can be propagated some other way in addition to seed.
For example, in addition to being grown from seed, gladiolus can be produced from bulbs.
African violets can be propagated from seed and by leaf cuttings. In this way, if you find anything good, you can maintain it.
Trying to purify plants so they will breed true from seed is difficult and is best left to the professionals.
Be sure to choose a plant that you can handle. For example, if you want to breed oak trees, you will need a forest and a lot of patience.
Grow Hundreds Of Plants
The minimum number of plants you will grow will be in the hundreds.
If you do not have land for a hundred plants, better try something else unless you are exceptionally lucky.
However, it is possible to get an outstanding hybrid with one seedling!
Essence Of Hybridization: Plant Improvement
The objective of breeding is plant improvement.
The purpose of hybridization is to combine the desirable characteristics found in two or more plants in one plant.
Crossing Two Plants
If you have a plant that has exceptionally attractive blooms but tends to be a poor grower and another that is vigorous but with a rather poor flower, what would be more natural than to hybridize (that is, cross) the two plants and select one of the offspring that is both vigorous and comely.
Herein lies the essence of hybridization. Cross plants that contribute something desirable, and then select a seedling containing a preponderance of the desired characters.
You must realize that there will be plants from this cross that are both non-vigorous and have poor flowers.
There may be many plants that have intermediate vigor and somewhat attractive blooms.
This is either good or bad, depending on whether you are an optimist or a pessimist.
Never lose sight of the fact that the desired plant is the one combining the greatest vigor with the most beautiful flower.
These plants may be rare, and it may be that none of the offspring measure up, so you will have to take the best plant and cross it again.
Whether this is preferable to repeating the original cross depends on how good the new seedling is.
The greater the population of plants, the greater your chance of success.
However, the most important thing is to make the correct cross in the first plant.
It is found that specific crosses will yield many desirable seedlings while other crosses give consistently poor results.
The way to find out which crosses are good is to make many of them.
When a fine cross is found, it will be possible to emphasize this cross.
Often a particular plant that produces consistently good offspring will be found, and this should be utilized.
Applying The Pollen
Crossing two plants is achieved by applying one plant’s pollen onto the other plant’s stigma.
Crossing two plants usually makes no difference in which plant is used as the pollen source.
If one plant has sterile pollen, this plant will have to be used as the “female” parent.
It usually pays to use the most vigorous plants as the “female” parent to get a maximum seed set.
If everything goes right, the pollen will form a tube and grow down the pistil style and fertilize the egg cell, which is now destined to grow into a seed.
The problem is to get only the pollen of the plant you want to grow.
Competition between insects, who drag pollen around on their feet, and hybridizers often becomes intense.
To further complicate things, many plants normally supply their own pollen.
Wind pollination offers additional difficulty. Techniques to get around these obstacles will depend on the structure of the particular flower involved.
In general, the following procedures can be followed.
Removing Stamens And Closing Of Flower
In plants, having flowers with both stamens and pistils, the stamens must be removed before they have shed pollen. This is done before the flowers open.
With a few exceptions, anthers do not shed pollen until the flowers are open.
Keeping insects away can be accomplished by removing the main attraction—the petals.
If this causes excessive injury and interferes with seed setting, insects may be excluded by closing the flower, after pollination, with cellophane tape.
Various bags have also been used, but these may be unsuccessful as the bags often act as heat traps.
A little cotton over the stigma may achieve the same results with little or no injury. The best insurance against contamination is to apply generous amounts of pollen to the stigma.
Collecting Pollen
Pollen can be collected by picking the anthers into a glass.
When dry, it can be applied to the stigma with the finger or with a camel’s hair brush.
In some plants, it is practical to pollinate by using the whole flower as a brush.
Dry the pollen overnight before using it by spreading it on a sheet of paper.
When applied to your finger, pollen should be shed from the anthers to appear as powdery dust.
If necessary, dried pollen may be stored for a considerable time under refrigeration.
Keeping The Harvested Seed Cool
When the seeds are harvested, they can be planted the following spring if greenhouse facilities are unavailable.
Be sure to keep the seeds cool and dry during the winter.
A good method is to keep them in a plastic bag together with a drying agent such as calcium chloride.
Keep in a cool spot. The seeds will remain viable for years if properly stored at 33° degrees Fahrenheit with low humidity.
Seedlings need a reasonable amount of care. Make every effort to treat all plants similarly.
If you allow some plants the benefit of good care while others suffer neglect, it will be tough to determine which seedlings are actually superior.
Keeping Records Of Dates And Labels
Be especially careful to keep a record of what you do. For example, keep a record of dates, and other pertinent notes, such as weather conditions.
Be sure to label all crosses with a tag that will last over the season and use a waterproof pencil.
Properly Evaluate Your Seedlings
In addition, be especially critical of the plants you save. Be generous in your initial selection, and then carefully cull down the list.
Be careful, however, not to throw away anything valuable.
The art of plant breeding is largely a problem of properly evaluating your seedlings.
Finally, after you have started, try to develop a program rather than make aimless crosses.
Make a study of the various breeding methods available. Do not be disappointed if success is not immediate.
Remember that distilling desirable characters into one plant is the most important factor in horticultural progress.