Tree propagation and maintance

Question 1

Sexual reproduction

Answer 1

• Sexual reproduction
• Genetic recombination from 1 or more
  parent trees
• Unpredictable outcome

Question 2

Asexual Reproduction

Answer 2

• Asexual reproduction
• Same genetic material as parent tree
• Predictable outcome

Question 3

Propagation

Answer 3

• 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

Question 4

Natural vs managed propagation

Answer 4

• 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

Question 5

Sexual propagation

Answer 5

• Seed fall (natural) or seed collection (managed)
• Germination (natural or managed)
• When conditions are right

Question 6

Cost of sexual reproduction

Answer 6

• 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

Question 7

Sexual propagaiton (stratification)

Answer 7

• 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

Question 8

Sexual propagation (scarification)

Answer 8

• 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)

Question 9

Asexual reproduction features

Answer 9

• 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

Question 10

Layering

Answer 10

• 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

Question 10

Grafting

Answer 10

• 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

Question 10

Maximising success rate of propagation

Answer 10

• 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

Question 10

What does a nursery do?

Answer 10

• Nursery produces trees for transplanting out into the
  landscape
• Bare root, ball and burlap, or container-grown trees

Question 10

Cutting

Answer 10

• 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

Question 11

Bare root tree features

Answer 11

• Field grown
• Undercutting and wrenching
  produces dense, fibrous root
  system → hardens tree against
  eventual transplant

Question 12

Ball and burlap tree features

Answer 12

• 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

Question 13

Container-grown tree features

Answer 13

• 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

Question 14

Tree end use

Answer 14

• 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

Question 15

Root biomass

Answer 15

• 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

Question 16

Root defects

Implications

Answer 16

• 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

Question 17

To prevent root defects

Answer 17

Containerised stock
should be replanted
into successively
larger pots before
their roots reach the
edge of the container

Question 18

Root desiccation

Answer 18

• 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

Question 19

Staking or guy wires

Answer 19

• 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

Question 20

Weed/Grass Competition

Answer 20

• 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

Question 21

Growing Media

Answer 21

Implications for optimal growth in nursery, transportation, post-transplant survival due to water loss, production and planting cost.

Question 22

Potting mix used in containers features

Answer 22

• 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

Question 23

B&B and bare root are field grown

Answer 23

• 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

Question 24

Irrigation and fertilisation

Answer 24

• 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

Question 25

Stocking implications

Answer 25

• 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

Question 26

Root ball weight of different production methods

Answer 26

• 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

Question 27

While in production temporary storage may need to be used to prevent descication …

Answer 27

This has an implication on tree survival, production and planting costs

Weather and logistic traits may also be why trees require to be stored

Question 28

Each different production techniques has implication on the easy of planting