Teaching Organic Farming & Gardening

Propagation/Greenhouse Management

Unit 1.3 | Part 1 – 99
Lecture 1: Seed Biology, Germination, & Development

Lecture 1: Seed Biology, Germination, &

Development—Environmental Conditions

& Cultural Requirements

Pre-Assessment Questions

1. What are the advantages of propagating annual vegetables in a greenhouse or similar
   climate control structure compared to direct seeding crops?


2. What conditions must be met for a seed to successfully germinate and grow into a viable
   seedling?


3. What are the key environmental conditions that facilitate germination and influence
   seedling development of annual vegetables?


4. What are the characteristics of seedlings when ready for transplanting to the field or
   garden? What actions may growers take to prepare seedlings for transplanting into the
   garden or field?


5. What is the most effective way to manage/prevent the development of pest and diseases
   in a propagation facility? Where would you seek information to identify pests or pathogens
   and to find Organic Materials Review Institute- (OMRI-)/National Organic Program-certified
   active control options if pest and or diseases should affect your seedlings?

A. Sexual Propagation

1. Definition: The intentional reproduction of a new generation of plants by the germination
   and growth of seeds that were created in the previous generation through the fertilization
   of a plant ovary via the union of male and female sex cells. Results in a genetically unique
   plant generation.

For comparison, asexual propagation is the reproduction of plants by means of division,
cuttings, tissue culture, etc. This process occurs in nature, but is a primary method for
reproducing many ornamental cultivars and the vast majority of fruits, berries, and nuts.
Clonal or asexual propagation results in a new generation of plants genetically identical to
the parent or source plant, thus carrying forward all desirable/known characteristics in a
predictable manner.

2. Types of plants grown from seed

a) Annuals: Plants that germinate, grow vegetatively, flower, and produce seeds, thus
completing their entire life cycle within a single year. Sexual propagation (propagation
using seeds) is the only practical means of propagation for annuals.

b) Biennials: Plants that complete their entire life cycle within two years. Growth is
primarily vegetative in year one. In year two, growth is directed primarily toward
reproduction in response to vernalization: The process wherein plants are exposed
to decreasing day length and temperature followed by increasing day length and
temperature. This process occurs in temperate climates when plants go from one
growing season, through Winter and into the following Spring. Sexual propagation is
the only practical means of reproducing biennial crops.