Tree propagation and maintance Flashcards
Sexual reproduction
- Sexual reproduction
- Genetic recombination from 1 or more
parent trees - Unpredictable outcome
Asexual Reproduction
- Asexual reproduction
- Same genetic material as parent tree
- Predictable outcome
Propagation
- Producing new trees from the seeds
or vegetative tissue of parent trees - Sexual propagation
- Seeds
- Asexual propagation
- Cuttings, rhizome, stolons, adventitious
buds, suckering, tissue culture
Natural vs managed propagation
- Natural – Seeds or vegetative tissue produce new trees in
nature - Excludes human intervention
- e.g., natural regeneration
- Managed – Seeds or vegetative tissue produce new trees under
managed conditions - Includes human intervention
- e.g., clonal propagation for plantation forestry
- Used for amenity/urban, horticulture, plantation forestry
Sexual propagation
- Seed fall (natural) or seed collection (managed)
- Germination (natural or managed)
- When conditions are right
Cost of sexual reproduction
- Flowering and fruiting is costly, so environmental resilience is
necessary (reason for reproduction beginning in mature state) - If photosynthetic yield is poor only vegetative buds, no
reproductive buds for next year
Sexual propagaiton (stratification)
- Period of cold (and possibly moisture)
followed by warmer conditions - Achieved under natural conditions by
transition from winter into spring - Buried or in contact with soil
- Achieved under managed conditions
by temporary cold storage - In a medium of e.g., sand, sawdust, peat
- Breaks embryonic dormancy
- Germination follows
Sexual propagation (scarification)
- Seed coat can be impermeable to
water and gas → helps to delay
germination - Seed coat needs to be broken down to
allow germination: - Mechanical (e.g., freezing)
- Thermal (e.g., fire)
- Chemical (e.g., digestion)
Asexual reproduction features
- Vegetative or asexual reproduction
- No need for flowers, cones, fruits, and
seeds - Natural
- Rhizomes, stolons, adventitious buds, suckering
- Managed
- Cuttings, grafting, layering, tissue culture
- All will produce genetically identical
offspring from the parent plant without
need for seed
Layering
- Roots grow from tree tissue that was
previously above ground - Tissue in contact with ground can be
intentionally wounded to promote
adventitious tissue growth → turns into roots - New tree continues to be supplied with water,
nutrients and photosynthates from parent
tree - Eventually above-ground tissue decomposes,
new tree separates from parent tree
Grafting
- Tissue from one tree (scion) is
attached to another tree (root
stock) - Vascular tissues repair themselves and
bind together - Ability to optimise both the scion
and root stock for desirable
attributes
Maximising success rate of propagation
- Success of propagation is called ‘taking’ or
‘striking’ - Striking for layering and cuttings can be
improved by: - Rooting hormone
- Auxin-based powder or liquid that promotes root
growth - Maintaining moist soil environment
- Maintaining humid air
- Success depends primarily on water balance
What does a nursery do?
- Nursery produces trees for transplanting out into the
landscape - Bare root, ball and burlap, or container-grown trees
Cutting
- Plant tissue removed from parent plant and
partially buried in rooting media - part of the shoot or root
- 5 – 15 cm for soft wood and 20 – 25 cm for hard
wood - Small hardwood cuttings (~30 cm) called wands
- Large hardwood cuttings (> 1 m) called poles
(poplar/willow) – above forage line - Cutting develops new roots and shoots - same
genetic material as parent plant
Bare root tree features
- Field grown
- Undercutting and wrenching
produces dense, fibrous root
system → hardens tree against
eventual transplant
Ball and burlap tree features
- Field grown
- Undercutting and wrenching
produces dense, fibrous root system
→ hardens tree against eventual
transplant - Large root ball, covered by soil, dug
and wrapped in burlap and wire
basket
Container-grown tree features
- Containers vary in volume and structure
- Soft-walled fabric or plastic planting bags
- Not reusable
- Hard-walled plastic pots
Causes root defects although root pruning pots can mitage this
Tree end use
- Production size depends on end use
- Plantation forestry, small size (< 30 cm in height)
- Bare root or container
- Amenity/urban, large size (> 200 cm in height)
- Bare root, container, or B&B
- Restoration, small size (< 30 cm in height)
- Bare root or container
- For commercial horticulture, grafting is most common → skipping juvenile stage
Root biomass
- Implications for posttransplant survival
- Root biomass retained by
containers - Root biomass may be
removed at time of planting
to correct defects - Undercutting, wrenching
and/or tree spade removes
large proportion of roots
from bare root and ball &
burlap trees, but produces
a fibrous root system
Root defects
Implications
- Implications for post-transplant
survival - Long-term problem
- Container can create circling,
kinked, girdling, or bound roots - Defects not always visible with
containers - B&B and bare root are generally
free of defects
To prevent root defects
Containerised stock
should be replanted
into successively
larger pots before
their roots reach the
edge of the container
Root desiccation
- Implications for posttransplant survival
- Soil remaining in
contact with roots in
containers and B&B
productions types
minimises root
desiccation - Bare root susceptible to
desiccation
Staking or guy wires
- Implications for stability,
production cost - Containerised trees are
susceptible to instability - Field-grown B&B and
bare root trees produce
anchoring structural
roots - Undercutting and/or
wrenching may lead to
temporary instability
Weed/Grass Competition
- Implications for water/nutrient availability,
production cost - Container-grown trees subjected to little
competition - Limited by surface area of container
- Easily removed
- B&B and bare root are field grown, so
competition can be significant - Weeds/grass can be removed mechanically or
chemically or with mulching at a cost
Growing Media
Implications for optimal growth in nursery, transportation, post-transplant survival due to water loss, production and planting cost.
Potting mix used in containers features
- Mainly organic material (e.g., peat, bark), but can
include coarse sand - Light weight → good for transportation/handling, but
loses water to surrounding soils post-transplant - Sterilised → avoids weeds and pathogens or diseases
- Fertilised → slow-release fertiliser to provide nutrients
- pH → appropriate for species being grown
B&B and bare root are field grown
- Heavier soils → better water retention, but poor for
transportation/handling (B&B only) - Fine-scale control over pH, fertilisation is more difficult
- B&B takes soil to destination, bare root leaves soil at nursery
Irrigation and fertilisation
- Implications for water/nutrient
availability, production cost - Container-grown trees have access to
limited soil volume, so water and nutrient
availability may be limiting - Irrigation systems provide required water
and nutrients to containers - B&B and bare root trees are field grown,
so water/nutrient availability is less
limited → large soil volume - Drought or nutrient poor soils still require
management
Stocking implications
- Implications for production cost, economies
of scale, pricing for consumers, profit for
growers - Container-grown trees can be grown
intensively - Bare root can be grown somewhat
intensively, but require space between rows
for undercutting/wrenching machinery - B&B are grown extensively, thus allowing
tree spade access to disinter tree for
transplanting - Smaller trees can be balled and burlapped by
hand, requiring less access space
Root ball weight of different production methods
- Implications for handling
and transportation →
production and planting
costs - B&B very heavy,
requires specialised
machinery - Bare root light, can be
moved by hand, by
individuals - Container weight
depends on size
While in production temporary storage may need to be used to prevent descication …
This has an implication on tree survival, production and planting costs
Weather and logistic traits may also be why trees require to be stored
Each different production techniques has implication on the easy of planting