1. Origin of Woody/Ornamental Cultivars
Plant Propagation

2. Cultivars The word cultivar stands for “cultivated variety”.
A cultivar is a manmade and/or man-maintained variety of plant.

3. Nomenclature
In a scientific or botanical name the cultivar name is written in single quotation marks and follows the species name.
Example: Clethra alnifolia ‘Hummingbird’

4. Cultivars versus the species
Cultivars are considered “improvements” over the species from which they were selected.
Examples:
Better flower color
Longer bloom time
Thornlessness
Variegated foliage
Improved disease resistance
Compact or dwarf growth habit

5. True-to-Type
Most cultivars of woody/ornamental plants will not come true-to-type from seed.
They are maintained by vegetative or asexual propagation.

6. Exceptions There are some exceptions…
Some vegetable and flower cultivars are sold as seed.
The seed of these cultivars is commercially produced by crossing (hybridizing) two parental lines of plants.
Examples: hybrid corn
Petunia, Marigold, Pansy, Salvia, and Impatiens

7. Hybridization of Parental Lines
A parental line with the genotype:
AABBCC
when crossed with another parental line of the genotype:
aabbcc
100% of the seed produced will be the genotype: AaBbCc
This is an example of a “sexually” produced cultivar.

8. Cultivar Origination
In general, cultivars of woody/ornamental plants can originate in 3 different ways:
Selection
Hybridization/Selection
Genetic Mutations/Selection

9. Selection
In any population of seedling plants one would expect to find considerable variation between plants.
What are some of differences you might see between different plants of the same species growing in a forest setting?

10. Selection
In “selection” an individual plant, with some desirable quality, is identified from a population of plants and subsequently propagated vegetatively.

11. Selection
In this example the “desirable quality” that has been selected is the darker green foliage.

12. Resulting Plants are Identical
Selection
Vegetative
Propagation
Resulting Plants are Identical
to the Selected Plant
Selected
Plant

13. A Practical Example
Acer rubrum ‘Northwood’ was selected from a native stand of Red Maples near the town of Excelsior, Minnesota.

14. Hybridization/Selection
In plant hybridization 2 different plants are crossed with each other.
The resulting seeds are planted and the seedlings are evaluated.
After several years of field trials one of the progeny of the original cross is selected.

15. Hybridization/Selection
Plant A
Plant B 5
Hybrid Seeds
A x B X

16. Hybridization/Selection
Five seedlings (A x B) are grown-on and evaluated.
Eventually one plant is selected.

17. Hybridization/Selection
Selected
Plant
Vegetative
Propagation
Resulting Plants are
Identical to Selected Plant

18. A Practical Example
Viburnum x rhytiophylloides ‘Alleghany’ resulted from a cross, made in 1958, between Viburnum rhytidophyllum and Viburnum lantana ‘Mohican’.

19. Genetic Mutations/Selection
Alterations to the DNA of the chromosomes of meristematic cells can produce “branch sports” or “sports”.
Branch sports are branches or parts of branches that have different characteristics than the rest of the plant.

20. Anthony Waterer Spirea with various chimeric patterns
Anthony Waterer Spirea with various chimeric patterns. Michelle Grabowski

21. Variegated rose seedling that is likely a periclinal chimera
Variegated rose seedling that is likely a periclinal chimera. David Zlesak

22. Branch Sports The branch sport is circled in red.
After a sport has been identified
it can be vegetatively propagated to see
if it will remain stable. Eventually it may
become a new cultivar.

23. Identical to the Branch Sport
Branch Sports
Vegetative
Propagation
Cuttings are removed
from the branch sport
Resulting Plants are
Identical to the Branch Sport

24. Practical Examples
The seedless navel orange was selected from a branch sport of a “normal” orange tree bearing seeded fruit.
Picea glauca conica (Dwarf Alberta Spruce) was selected from a branch sport of Picea glauca.

25. The End