Introduction to Horticulture

Horticulture

A branch of agriculture concerned with intensively cultured plants used for food, for medicinal purposes, or for aesthetic gratification.

Pomology

The area of horticulture that focuses on fruit production.

Olericulture

The area of horticulture that focuses on vegetable production.

Floriculture

The area of horticulture that focuses on flower production.

Landscaping

The use of plants for beautification of an area.

Scope in Ireland

Horticulture is the 4th largest agricultural sector in Ireland, with over 2% of land devoted to it and a 'farm-gate' value of approximately €467 million in 2020.

Interdisciplinary Nature of Horticulture

Horticulture draws upon a wide range of scientific disciplines, including Biology & Botany, Pathology, Zoology, Soil Science, Ecology, Physics and Engineering, Business and Economics, Social Sciences & Psychology.

Value to Growers & Horticulturalists

Market values and jobs associated with horticulture.

Value to Individuals & Communities

Basic living needs and mental well-being provided by horticulture.

Social Horticulture

Application for enrichment and health of individuals and communities, contributing to Social Capital.

Vegetative Propagation

A method of creating new plants that are genetically identical 'clones' of the parent plant.

Plant Propagation

The process of creating new plants.

Asexual Propagation

Propagation that involves producing a new plant from a sole parent, using a part of tissue, such as a piece of stem, leaf or root.

Sexual Propagation

Propagation that involves the use of seeds.

Totipotency

Plant cells are capable of forming any cell type.

Advantages of Vegetative Propagation

Uniformity in crop, rapid bulking, propagation of plants that do not produce viable seeds or have a long-life cycle, and removal of viral diseases.

Clone Variations

While clones are genetically identical, mutations can cause variations due to errors during DNA replication, exposure to mutagenic agents, or viral infections.

Cuttings

Involve removing a piece of the parent plant (stem, root, or leaf) that regrows lost parts.

Types of Cuttings

Stem cuttings are categorized as Softwood, Semi-Hardwood, and Hardwood based on the plant tissue's maturity.

Rooting Powder

Contains auxins like IBA and NAA to encourage root development.

Callus

A mass of undifferentiated cells that forms after cutting.

Division

One of the easiest ways to propagate perennials, typically done in spring or autumn.

Tubers

Modified underground plant stems serving as storage organs (e.g., potatoes are tubers from stolons).

Rhizomes

Modified underground plant stems serving as storage organs (e.g., ginger is a rhizome).

Seed Pieces

Used in vegetative propagation of potatoes, which are cut and allowed to suberize to prevent decay.

Layering

Stems are rooted while still attached to the mother plant, encouraging adventitious roots.

Techniques of Layering

Includes Tip-Layering, Stem-Layering (or simple-layering), Serpentine Layering, Trench-Layering, Air-Layering (marcotting), and Mound-Layering.

Grafting

Involves joining a 'scion' to a 'rootstock' where the scion provides the top, fruit-bearing part and the rootstock provides the root system.

Budding

A method that uses a single bud as the scion to join with a rootstock.

Compatibility

The crucial aspect of ensuring that the scion and rootstock can successfully join together.

Interstocks

Used when incompatibility exists between the scion and rootstock.

Grafting Methods

Includes Approach, Wedge/Cleft, Splice, Tongue, Bark, Bridge, and Veneer grafting.

Budding Types

Includes T-budding, Ring budding, and Chip budding.

Micropropagation

Involves placing a small section of a plant in a controlled, sterile nutrient environment to produce new plantlets.

Advantages of Micropropagation

Includes small space requirements, production of pathogen-free plants, propagation of difficult species, and year-round propagation.

Propagation Environment

Factors influencing success include the Aerial Environment and the Growing Medium.

Aerial Environment

Includes factors like Humidity, Light, Temperature, and Air quality.

Growing Medium

Includes factors like Moisture level, Temperature, Aeration, pH, and Nutrient level.

Seed Propagation

Covers sexual plant reproduction through seeds, the most common form of horticultural propagation.

Genetic Variation

Plants propagated by seed are not always the same as the parent plant due to genetic variation or recombination.

Merits of Seed Propagation

Includes new plant variety introduction, low-cost production method, less risk of virus transmission, faster rate of establishment, and less restrictive import and export.

Pollination

The transfer of pollen from anther to stigma.

Fertilization

The union of male and female gametes.

Seed Structure

Seeds have three main parts: Seed coat, Endosperm, and Embryo.

Seed Germination Process

Starts with water absorption and ends when the new plant can photosynthesize.

Factors Affecting Germination

Includes viability of seed, environmental factors, and seed dormancy.

Viability of Seed

The potential to germinate, tested by seed companies using methods like the Tetrazolium test.

Water Availability

The most important factor for activating germination pathways.

Temperature

Reflects the plant's native climate and affects physiological processes.

Atmospheric Gases

Oxygen is required for respiration; high CO2 can reduce germination.

Light Requirements

Majority of seeds do not require light, but some do (e.g., petunia, celery).

Seed Dormancy

A survival strategy where seeds are prevented from germinating despite suitable conditions.

Plant Growth

Defined as a permanent and irreversible increase in the size of one or all plant organs.

Photosynthesis

How plants produce food using chlorophyll, carbon dioxide, water, and sunlight, with the formula 6CO2 + 6H2O + Sunlight → C6H12O6 + 6O2.

Respiration

Conversion of food into energy for growth and development, with the formula C6H12O6 + 6O2 → 6CO2 + 6H2O + Energy.

Formula for Cellular Respiration

C6H12O6 + 6O2 6CO2 + 6H2O + Energy (opposite of photosynthesis)

Transpiration

Water loss through stomata (primarily on leaf surfaces)

Functions of Transpiration

Transporting minerals, cooling the plant, moving sugars/compounds, and maintaining turgor pressure

Vascular System

Water and nutrients are transported via the vascular system (Xylem for water/nutrients from root to shoot, Phloem for food/energy from shoot to root)

Environmental Factors Affecting Growth

Water, Light (quantity and quality), Temperature (optimum for physiological processes), Air (gas exchange), Nutrients (obtained from soil/compost), Space (to avoid competition and pests/pathogens), and Time (life cycles vary)

Temperature

Influences growth rates and Dormancy (when the plant has stopped or slowed its growing process)

Encouraging Taller Growth

Strategies include restricting light (Etiolation), frequent watering, and increasing competition

Soil Texture

The proportion of sand, silt, and clay affects nutrient holding capacity and drainage

Plant Life Cycles

How long a plant takes to grow, flower, and set seed

Annual/Ephemeral Plants

Completes life cycle in one season

Biennial Plants

Plants that take two years to complete their life cycle

Perennial Plants

Plants that live for three or more years, with herbaceous or woody stems

Basic Plant Structures

Roots (anchorage, water/nutrient absorption), Stems (support, transport via vascular system), Leaves (photosynthesis, transpiration), Flowers (reproductive part, modified leaves), Fruits (ripened ovary containing seeds), Seeds

Pomology

The study and production of fruits

Definition of Pomology

The study of fruits is called pomology, derived from Latin 'pomum' (fruit)

Botanical vs. Horticultural Fruit

Botanically, a fruit is a ripened ovary; horticulturally, it's the edible, fleshy or dry portion of a plant closely associated with the flower

Orchard

An area for commercial fruit production ('orcharding'), typically based on long-lived perennials

Deciduous vs. Evergreen

Deciduous sheds leaves in autumn/winter; Evergreen has persistent leaves

Juvenile vs. Mature Phases

Juvenile phase is vegetative; Mature phase is reproductive

Small or Soft Fruits

Fruits borne on low-growing plants like shrubs/vines, e.g., grapes, strawberries

Nuts

Edible seeds, e.g., almonds, walnuts

Fleshy Fruits

Fruits where the edible part is soft flesh

Fruit Classification based on Temperature

Temperate Fruits (mostly deciduous, require chilling to flower), Subtropical Fruits (frost sensitive), Tropical Fruits (very sensitive to low temperatures)

Systematic Pomology

Describes fruits by structural development: Pomes, Berries, Stone fruits/Drupes, Aggregate fruit, Multiple fruit

Fruit Production Practices

A year-round effort involving various techniques including Growing environment management, Nutrient management, Pruning/training, Disease and insect control, Planting and post-planting care, Crop load management, Plant material selection, Weed control, Harvesting, and Water management

Training and Pruning

Crucial for apple tree maintenance and fruit production; Training guides tree growth, while Pruning removes a portion of the tree

Summer or Winter Formative Pruning

Done in the first 3-5 years to select branches

Dormancy Pruning

Typically an annual occurrence done during dormancy in Winter to remove unwanted branches when energy is stored

Summer Pruning

Eliminates photosynthetic potential and reduces growth, limited to removing upright branches and avoided after late July to prevent winter injury

Central leader

A training system used in orchards.

Slender Spindle system

A commercial system that uses dwarfing rootstocks and requires support.

Cordon

A method of training plants along a wire or support.

Espalier

A technique of training plants to grow flat against a support.

Fan

A training method where branches are spread out to form a fan shape.

Step over

An ornamental training method for plants.

High density planting

A method used in commercial orchards that involves planting more trees per hectare.

Biennial Bearing

A phenomenon where extensive pruning can lead to a year without fruit production followed by a year of heavy fruiting.

Root Structure

Includes primary root (tap-root for anchorage), lateral roots, and root hairs.

Geotropism

The ability of roots to sense and respond to gravity due to statocytes.

Primary Root Functions

Include absorbing water & minerals, support & anchorage, and food storage.

Secondary Root Functions

Include forming symbiotic bonds with microbes and preventing soil erosion.

Root Microbiome

A community of microbes living in association with roots, exhibiting different relationships.

Mutualism

A relationship where both plant and microbe benefit.

Commensalism

A relationship where one organism benefits without harming or benefiting the other.

Parasitism

A relationship where one organism benefits at the expense of the other.