There are numerous characteristics that one can breed for in an ornamental plant: color, shape, size, substance, hardiness. All of these can be applied to leaf, plant or flower. Sometimes a plant is too vigourous or spreads too easily and must be tamed for the garden. This page is devoted to the techniques to do this.
 

Topics:

1.     Being the Bee:  Pollen Daubing for Fun and Profit
2.     Doubling Up: Tetraploid Conversion
3.     Slimming Down: Triploid Reduction
4.     Makeup! Introducing Variegation
5.     Naming the Baby: Cultivar Registration

This is basic. Nearly every plantsperson sooner or later sees a plant with desirable characteristics that they want to conserve or has the urge to create a "new" or "improved" plant.

Techniques
    Preventing self-pollination
    Keeping out the bees
    Catching the seed

Chromosome counts:

Hibiscus syriacus:
Tropicos: gametophytic count: 40; IPCN reference: 90-91 Sidhu, M. K., R. C. Gupta & N. Goyal, 1990.
    Title:  SOCGI plant chromosome number reports---IX
    Publication:  Journal of Cytology and Genetics
    Collation: 25: 145

Hibiscus sinosyriacus:
Tropicos: gametophytic count:
 

There are many reasons to double the chromosomes. In general, a tetraploid is sturdier than the mother plant in all its parts: stems, leaves and flowers. Sometimes it is done to improve inter-species fertility for hybridization. Other times it is done to reduce cross fertility with the normal plant in order to "tame" it.

Techniques and Chemicals

1.       Preparing the Solutions
2.       Oryzalin Conversion of Lilies
3.       Monocots vs. Dicots
4.       Three  methods of attempting colchicine conversion on bulbs
5.       Colchicine Concentrations
6.       Other Colchicine techniques for Iris
7.       Other Surflan Techniques
8.       Polyploid Conversion of Daffodils
9.       Other Chemicals

Triploid reduction is usually done to "tame" a plant. Some plants' seed is just too vigorous in the garden. These plants are frequently called "weedy" and are considered a pest, even though they may be very desirable in other ways.

Leaf color changes can be obtained through natural mutation and selection or the odds can be improved with certain techniques: irradiation (both x-ray and gamma) and mutagenic chemicals have been used.

Most often the variegated plants are chimeras, with some of the cells having lost their chloroplasts.  Chimeras are useless for breeding... the trait is not inheritable. Sometimes you can get this with UV light on the meristem.

It is important to give improved plants a name and to register that name. This process is standardized by by the International Society for Horticultural Science through its Commission for Nomenclature and Registration, who appoint International Registration Authorities.