Distance Education Course
- Learn to select, grow and manage cut flower crops in a greenhouse.
- Develop your plant knowledge, horticultural expertise and awareness of the greenhouse production industry
- Work in the Cut flower industry, start a business or further your career opportunities
There are 12 lessons in this course:
Introduction to Cut Flower Production
Flower Initiation & Development
Pest and Disease Control
Greenhouse Management A.
Greenhouse Management B.
Management, Harvest & Post Harvest
Annuals & Biennials
Bulbs, Corms, Tubers & Rhizomes
To describe the nature and scope of Cut Flower production in greenhouses.
To determine key cultural practices that are commonly required to develop and maintain a good rate of growth in a cut flower crop.
To explain the initiation and development of flowering in a cut flower crop.
To determine management practices for cut flower crops grown in a greenhouse
To discuss a range of greenhouse management techniques related to cut flower production.
To explain a range of greenhouse management techniques related to cut flower production.
Determine a range of harvest and post harvest techniques related to cut flower production.
Determine greenhouse production techniques for selected herbaceous perennials.
Determine greenhouse production techniques for selected annuals and biennials.
Determine greenhouse production techniques for selected bulbs, corms, rhizomes or tubers.
Determine greenhouse production techniques for selected filler plants.
Determine greenhouse production techniques for roses, and for orchids.
Tips for Managing Flowering in a Greenhouse
Flowering occurs when there is a sudden change in the growing point, from vegetative organs (i.e.: leaves, stems, leaf buds) to floral organs. When this happens, the apical dominance (i.e. the dominance of the growth in the upper end of stems that inhibits growth of lateral buds) usually weakens.
The initial stimulus to cause this change in tissue type appears to normally originate in the leaves (though not always). Some target cells or tissues are stimulated by a fairly non specific trigger, setting off a chain reaction (cascade) throughout the involved tissue. Much work has been done trying to discover the chemistry of these changes, but the results tend to only show that there is a very great complexity involved.
As flowering tends to be related to particular times of the year, the initial stimulus is most obviously environmental. There are three possible types of environmental stimuli:
- Physical eg: Changes in photoperiod (longer/shorter days), humidity, pressure
- Electrical e.g: Changes in pH
- Chemical: Changes in levels of certain chemicals eg: More light increases photosynthesis, which increases levels of sugar in the plant
There are two types of chemicals involved both promoters and inhibitors. The promoters stimulate the process of flower induction. The inhibitors inhibit this inductive process. The promoters & inhibitors do not work together in a balancing interaction. They affect each other through an interference process.
(eg: With Kalanchoe, short days produce promoters, but if more than one third of the days are long, sufficient inhibitors are produced to stop the affect of the promoters).
JUVENILITY is a completely different thing to the effect of inhibitors. A plant cannot respond to the affect of flowering promoters until tissue has gone through a phase change to reach maturity. It is possible for this phase change to be reversed and mature tissue become juvenile again.
Types of flowering response to temperature
Temperature can affect time of flowering from sowing, three different ways:
- Vernalization where cold temperature hastens flowering.
- Rate of flowering process increases over a sequence of different temperatures. The final stage is an optimum temperature where flowering is most rapid.
- Supra Optimal Temperatures Stressful temperatures which delay flowering as temperatures become warmer.
Ways to cause controlled flowering
If the plant suffers juvenility problems, then propagation can be done vegetatively eg: Boronia will only flower if the plant is a mature established one. A Boronia raised from seed will not flower for some time, but if a plant is grown from a cutting off an established plant it will flower sooner.
- Photoperiod: changes in exposure to sun light will trigger flowering in some species
- Type of light (eg: red light on short day or long day plants)
- Gas eg: Carbon Dioxide enrichment on short day plants. Lack of carbon dioxide availability to leaves stops flowering production.
Principles affecting rates and progress of flowering
- Rates and progress toward flowering, virtually always, bears a linear relationship to either photoperiod or temperature or both. eg: As temperature increases, flowering increases or progresses towards development. The more temperature, the more flowering. Or as temperature decreases, flowering increases or as light increases, flowering decreases, etc.
- The basic temperature response (not affected by photoperiod) is applicable to almost all annual crops.
- A photoperiod temperature response is common to all photoperiod sensitive plants. Photoperiod sensitivity varies among species & cultivars. The greatest sensitivity is with tropical (short day) plants where differences between day lengths are very small. In this case the response is to mean temperature usually.
- Environment insensitive plants generally have no response to either mean temperature or photoperiod.
- Where temperatures are excessively above optimum levels there is a negative, lineal relationship, between mean temperature and flowering. Most generalizations refer to non stress temperatures.
- Variable daily contributions by photoperiod & temperature conditions can be treated as additive increments towards flowering.
Applied flowering control
There have been a few cases where treatment with auxin (hormone) or ethylene generating substances has induced flowering (eg: Bromeliaceae)
There is more likelihood in the near future to finding chemical inhibitors to flowering rather than chemical stimulants. Inhibitors would be useful to stop pasture grasses from flowering, for instances.