3. Horticultural Technology for Landscape Horticulture

The main technologies associated with landscape horticulture are:

• Propagation
• Plant nutrition
• Plant establishment
• Growth Regulation - Training, pruning, chemicals
• Interactions with other organisms - Plant Protection

Propagation

• The multiplication of plants by sexual and asexual means

  - sexual propagation

  by multiplication of seedlings from seeds (most vegetables, ornamental annuals and biennials)

  - asexual propagation

  by multiplication of vegetative parts (cuttings, budding, grafting, meristemming, layering, divisions)

• Knowledge of genetics and breeding systems, physiology, anatomy, and plant development is extremely important in propagation.
  • Understanding genetics helps explain the variability associated with propagation by seed.
  • Understanding physiology, anatomy, and development helps intelligent selection and manipulation of plant parts for successful rooting and grafting. For example, understanding dormany requirements and the techniques to overcome them (such as scarification and stratification) is crucial in the propagation of trees from seed (a necessary practice in ornamental horticulture).
• Most plant propagation and much production (of ornamentals) is done in containers with ammended soils or artificial media.

  Commonly used soil amendments:

  Sand, Peat, Sphagnum moss, Vermiculite, Perlite

Plant Nutrition

• Mineral nutrition affects most aspects of plant quality.
• Mineral deficiencies often affect plant growth both in fields, gardens or containers.
• Manipulation of plant nutrition can influence the development of plants. For example, abundant nitrogen tends to promote lush growth of vegetative parts, but may delay flowering and make the plant susceptible to environmental stresses such as drought.
• Use of fertilizers is essential in most production systems, especially those with artificial media
• NPK fertilizers, called balanced fertilizers, provide the three most critical mineral elements for plant growth. These fertilizers come in a wide variety of chemical and physical forms.

Establishment of Plants in the Landscape

• Environmental and physiological aspects are critical
• For example: working the soil prior to planting or transplanting is critical.

  Quality of plant material also critical

  - bare-root trees (up to 95% of root left behind)

  - container-grown trees (retain entire root system)

Growth Regulation

• Physical techniques for controlling shape, size and direction of plant growth
  • Training = affecting the orientation of growth (e.g. staking tomatoes)
  • Pruning = judicious removal of plant parts (topiary = plant sculpture)

    Pruning may also be done primarily for adjusting fruit load as opposed to purposely affecting shape.

    Examples of controlling plant growth by selective pruning and training

    - bonsai

    - espaliers

    - pinching

    - girdling
    

• Chemical approaches to growth regulation
  • Growth regulators influence plant height, productivity, aggregation.
  • For example: IBA (Indole Butyric Acid) promotes rooting of cuttings.

Interactions between Plants and Other Organisms

Beneficial relationships

microbes (root nodules) - important for nitrogen fixation

insects (bees, etc) - important for pollination and fruit production

Detrimental relationships

weeds - crowd out horticultural crops

diseases (viruses, bacteria, fungi) - reduce plant vigor and quality, and often kill the plant

pests (insects, mites, nematodes rodents, etc) - reduce plant vigor or kill the plants outright and may transmit diseases

• Plant Protection - Control strategies for detrimental relationships
  • physical - removal of pests, cultivation to control weeds

    chemical poisons and repellents

    - pesticides: broad category of pest-controlling chemicals

    - herbicides (destroy weeds), insecticides (destroy insects), fungicides (destroy fungi), acaricides (destroy mites), nematicides (destroy nematodes)

  • biological -use of other living organisms to control pests (e.g., natural enemies)
• Problems with Chemical Controls
  • residues on edible products
  • technical problems of application
  • spray injury to the plant
  • development of genetic resistance by the pest
  • disturbance of the ecological balance
  • pollution
  • government regulations
• Rachel Carson: a key figure in the history of using chemical controls for plant protection
  • Government Scientist
  • Respected naturalist and popular writer ('The Sea Around Us')
  • Alerted the world to the dangers of excessive use of pesticides such as DDT
  • 'Silent Spring' (1962) - click to read some comments about this famous book.
• Possible Solutions to Problems with Chemical Control Strategies
  • Reduced use of pesticides - Integrated Pest Management (IPM)
  • Strict biological controls - 'organic' production
  • Develop more disease / insect resistant plant cultivars through breeding and biotechnology

An excellent place to learn about Biological Control is available from Cornell University. Check it out!

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