Horticulture #3

Light Duration

number of continuous hours of light in a 24-hour period

Light Quantity

number of light particles (photons) of different wavelengths (colors) that are capable of performing photosynthesis

Light Quality

spectral distribution of light (number of photons) emitted from a light source

Effect on Plant Growth

Photosynthesis

Pigment Formation

Seed germination

Fall color

Growth habit

Size

Flowering

Fruiting

Plant Pigments

Carotene (orange)

Xanthophyll (yellow)

Chlorophyll (green)

Anthocyanin (red)

Phototropism

A plant's response to light

What causes plants to "bend" towards light?

elongation of cells down the backside caused by a hormone

Auxin

Plant hormone produced in stem tip

Growth Occurs

Full sun (high light) area and plants that require full sun

No growth, slow death

Low light area and plants that requires high light

Light compensation point

Rate of photosynthesis equals the rate of respiration (energy burned to maintain life)

Light saturation point

Amount of light, beyond which no added benefit (growth) is obtained

Site Selection

What is key in where we put plants?

Shade leaves

Larger

Thinner

Greener

Lower light compensation point

More efficient photosynthetic apparatus

Sun Leaves

Smaller

Thicker

Less chlorophyll

Higher light compensation point

Less efficient photosynthetic apparatus

acclimatization- slowly change environment

Light

Temperature

Water

Nutrition

acclimatization- "Hardening Off" (before planting outside)

Vegetable transplants

Houseplants

Etiolation

plant grown in partial or full absence of light

Blanching

growing technique to exclude light

Sulphurous compound

What causes the distinct odor in urine when eating asparagus?

Genetics and Environment

Fall Color Influenced by

Decreasing day length

Decreasing temperatures

What stimulates the onset of fall color?

Fall Color: A Summary

Decreasing temps and photoperiod stimulated the formation of the abscission layer

Flow of water and nutrients slows

Production and flow of sugars slows

Chlorophyll synthesis slows down

Leaf fades in green goloration

Yellow and orange pigments show through

Yes... the yellow and oranges were always present in the leaf.. Just hidden!

What about reds?

Development of red pigmentation is a function of daily climatic conditions and...

Sugar accumulation in the leaf

The right combo leads to red pigment

What's the recipe for red leaves

Warm dry sunny days...

Cool dry nights

Sugar pool build up...

Night temps <45 stimulates the conversion of sugars to... anthocyanin

Keep in mind with red leaves

Fall climate influences sugar accumulation

Location influences climate

Microclimate matters

Photoperiodism

A plant growth response as influenced by the duration of light and darkness in a 24 hour day

Discovered in 1920 by Garner and Allard

Most prominent example: Flowering

Other response

Seed germination

Rooting

Abscission

long day plants (LDP)

plants that are stimulated to initiate flowering when the day length is longer

Short day plants (sdp)

Plants that are stimulated to initiate flowers when the day length is less

Day Neutral Plants

Plants that simply flower at some stage of growth with no regard to the length of day or night

Photosynthesis basic facts

100 billion tons of sugar produced by plants annually

94% of dry matter in plants from photosynthesis (6% from soil)

Only 1% of light that hits a leaf is used in photosynthesis

Only 1% of water absorbed by plants is used for photosynthesis

Photosynthesis light

6CO2 +6H20= C6H12O6+ 6O2

Plant propagation

use of seeds or vegetative plant parts to produce more plants

Sexual

Seeds

Asexual

Vegetative

Leaf

Stem

Root

Sexual Advantages

Less technology

Easy Shipping

Genetic diversity

New color textures, hybrids

Asexual Advantages

No reproductive pressure

Bigger plants faster

Flowering faster!

Clones & Nostalgia

Mutation preservation

Seed Sowing Depth

1.5 x diameter of seed

Seed selection & Info

Seed packets provide culture needs

Grow time varies by species and cultivar

Check sow depth

Plan ahead

Label Seeds!

Seed Sowing & Containers

Watch for tropisms. Tupos = turning

Phototropism

Gravitropism

Thigmotropism

vegetative propagation

Vegetative Parts:

Leaves

Stems

Roots

Vegetative propagation categories

Cuttings

Grafting

Layering

Division

Micropropagation

Auxin

Rooting hormone

Produced at shoot tips

Moves away from light

Cuttings root at the base of stem

Herbaceous

any time

soft wood

new growth

semi hardwood

seasonal growth

hardwood

old/dormant growth

Totipotency

cell's ability to differentiate into new tissues and become complete, fully functioning plant

Leaf cuttings

totipotency

Leaf sections- not bud required

Limited species can grow from leaf cuttings

Many plants from one leaf

Root cuttings

Specialized propagation method of some species

Carbohydrates stored in roots of dormant plants

Root cuttings aren't rhizomes

Scion

top portion develops into shoot

Rootstock

bottom portion develops roots

Grafting

Scion

Rootstock

Cambium tissue connection

Same or closely related species

Selected for mutual benefits

Disease resistance

Cold Hardiness

Structure and form

Pollination technique

WOW factor

Dwarf Citrus

Rootstock: Poncirus trifoliata 'Monstrosa' or 'Flying Dragon'

Height- 4-6'

Fruit- tart, 2" & seedy

Scion

Sitrus sinensis 'Washington' Navel

Height- 10-12'

Fruit- sweet, 4" & seedless

Grafted

Height- 3-5'

Fruit- 'Washington' Naval

SImple and Tip Layering

Bend flexible stem and bury in soil

Air Layering

Disrut Auxin transfer mid-step

Natural Layering

Stolons and runners

If environment is dark and moist

perfect for root growth

Division

Bonus propagation

Crown separated into smaller bud sections (Rhizomes, offsets & pups, or clumps)

Micropropagation

Tissue Culture

Multiplication of plants in vitro

Sterile conditions

Hormone manipulation

Goals:

Genetic preservation

Viral cleansing

Difficult-to-root species

Dramatic increase

Pruning

The removal of plant parts; shoots and roots

Reasons to Prune

Remove apical dominance

Promote flowering

Control plant size, shape, and access

Maintain plant health and appearance

Rejuvenation

Open the plant canopy

Specialty sculpting

Topiary & Espalier Formal Hedges Bonsai

Heading Back

reducing the entire plant size

Thinning

selectively reducing density

Hand pruners

Stems less than ½" in diameter

Loopers

Stems ½" ro 1 ½" in diameter

Saw (hand or chain)

Stems greater than 1 ½" in diameter

Hedge Trimmers

For sculpting / shaping

"Massacring plants"

Main Types of Hand Pruners

Bypass pruners & Anvil Pruners

Color Matters!

7

How many reasons to prune

Prune after flowering

Flower in winter or spring

Prune when dormant

Flower in summer of fall

Remontant Plants

A plant that blooms more than once a year

When to Prune Re-Bloomers

Immediately after their spring flowering for maximum bud set before the next flush

Pleaching

Raised hedge

Chateau Villandry (France)

Some improper Pruning

Crape Myrtle

Permanent Pruning

NO TOPPING

Topping

Removal of large upper branches without regard to location of the pruning cut

Dormant/ Latent Bud Break

Pruning Conifers

Conifers do not have dormant buds on their lower/ inner branches like angiosperms do

Prune only where there is green foliage

Dead zone

No dormant buds= no re-growth

Shearing Shrubs

Random actions of violence in the landscape

What to remove the maintain health of plant

Dead

Damaged

Diseased

Dying

Soil

Weather Rocks

Factors Influencing

Parent material

Time

Topography

Climate

Organisms

Soil Science

the study, analysis, and recommendations of soil for appropriate land use

Soil Properties

the physical, chemical, and biological characteristics that influence plant growth

What soil does for a plant

Support

Anchorage

Nutrients

Water

Oxygen

Major Soil Types

mineral and organic

Soil Microbiome

Diverse community of microorganisms living in the soil, playing crucial roles in nutrient cycling, soil health, and plant growth

Like bacteria, fungi, protists

Soil Porosity

the amount of pore space within a soil

Holds air or water

Cation Exchange Capacity (CEC)-

a soil's ability to hold and exchange positively charged ions on its surface

Infiltration

water seeps into the soil from the surface, moves down laterally

Influenced by soil type, topography, rainfall intensity

Leaching

water moves through the soil, beyond the rootzone

Can carry soluble substances luke fertilizers and pollutants with it

Runoff

water that flows over the soil/land instead of soaking in the ground

Influenced by: impervious surfaces, topography, soil compaction, soil type

Can carry pollutants into waterways

Soil Texture

Size and shape of soil particles

Sand (Texture)

.05 to 2mm / round

Silt (Texture)

.002 to .05mm/ round

Clay (Texture)

<.002 mm / plate/like

Sand Soil Type

Course textured

Drains freely= Lots of air

Holds little water

Low CEC

Doesn't compact

Changes temp quickly because it doesn't hold water

Loam Soil Type

Equal percents (sand, silt, clay)

Good drainage, aeration, water retention, CEC