Hort227 Lab Exam

why smoking is not allowed in propagation labs

Tobacco mosaic virus can be transferred from tobacco products, including chewing tobacco, to plant material used in labs.

why food and drink is not allowed in labs

there may be chemical residues on the bench in the headhouse or on the plants

why closed shoes must be worn during the lab

there may be bacteria, fungi, or pesticide residue on the floor; the floors may also be slippery

why sanitary practices are followed

* Wash your hands before and after propagating material.
* If plant material falls on the floor, such as a cutting, do not use it as pathogens can be introduced into your propagation flats.
* Keep tools and ends of hoses off the floor to avoid spreading of disease organisms

Types of disinfectants that can be used on propagation tools and equipment

Used to clean propagation tools, equipment, and table surfaces to limit the spread of pathogens

* Blue disinfectant liquid (cleaner) for tools and tables (in baby food jars)
* Bleach solution with water used for some surfaces, not on tools, as this will corrode them
* Lysol spray used in cleaning pruning equipment, easy to use
* Soaps to wash your hands prior to and after each propagation lab

pesticides

Any substance used either to directly control pest \n populations or to prevent or reduce pest damage.

* Not all pesticides kill the target organism; some may only inhibit its growth, repel it, or reduce its reproductive capacity.
* Pesticides can be insecticides, miticides, fungicides, bactericides,herbicides, rodenticides, etc.

the pesticide label

The pesticide label is a legal document. It is illegal to use the chemical in any manner inconsistent with the label.

* If you are injured without following the direction, then the manufacturer is not responsible.
* Increasing the rate of a pesticide is illegal and may actually damage or kill the plant

pesticide signal word: caution

* relative toxicity: low
* oral LD50 (mg/kg): >5,000
* Dermal LD50 (mg/kg) or Inhalation LC50 gas or vapor (ppm): >20,000
* Inhalation LC50 (mg/L) dust or mist: >20
* Approximate Oral Lethal Dose for 150 lb. human: >1 pint or 1 lb

pesticide signal word: caution

* relative toxicity: slight
* oral LD50 (mg/kg): 500-5,000
* Dermal LD50 (mg/kg) or Inhalation LC50 gas or vapor (ppm): 2,000-20,000
* Inhalation LC50 (mg/L) dust or mist: 2-20
* Approximate Oral Lethal Dose for 150 lb. human: 1 oz. to 1 pint or 1 lb

pesticide signal word: warning

* relative toxicity: moderate
* oral LD50 (mg/kg): 50-500
* Dermal LD50 (mg/kg) or Inhalation LC50 gas or vapor (ppm): 200-2,000
* Inhalation LC50 (mg/L) dust or mist: 0.2-2
* Approximate Oral Lethal Dose for 150 lb. human: 1 tsp - 1 oz.

pesticide signal word: danger/poison

* relative toxicity: high
* oral LD50 (mg/kg): 0-50
* Dermal LD50 (mg/kg) or Inhalation LC50 gas or vapor (ppm): 0-200
* Inhalation LC50 (mg/L) dust or mist: 0-0.2
* Approximate Oral Lethal Dose for 150 lb. human: a few drops to a teaspoon

Which is worst for humans: highly toxic if orally ingested or highly toxic if inhaled?

inhaled, must wear a mask

LD50

the amount of chemical required to kill 50% of a test population, usually white rats or mice.

* It is expressed as a ratio of weight of the chemical (product) to the body weight of the animal tested (mg product/kg weight).
* Besides oral LD50, there are also dermal (skin) LD50 numbers.

Which is a safer pesticide: LD 50 of 5 ppm or LD 50 of 1,000 ppm?

LD 50 of 5ppm

* The more dangerous the pesticide, the lower the LD 50 number, indicating that a smaller dose has the ability to kill the test population

LD 50 number and long term effects

The LD 50 number does not reflect the consequences of long-term exposure, such as cancer, birth defects, and reproductive toxicities that may occur below the fatal concentration

lighting used in the propagation mist room of the greenhouse

high intensity bulbs for supplemental lighting, high-pressure sodium lamps provide lighting on cloudy days; they’re turned off on sunny days and at night; they’re mainly used during winter - early spring when daylight hours are under 12 hrs

What controls the mist system/humidity in the propagation room in the greenhouse?

Sensors keep humidity high to prevent cuttings from drying out. Computer sensor kicks in mist system to raise humidity. A humid environment is essential during the propagation process as the cuttings are not taking up water until roots are transformed

properties of an ideal propagation media

1. Sufficiently firm and dense to hold cuttings upright or seeds in place
2. Volume must be fairly consistent when wet or dry
3. No excessive shrinkage after drying
4. Highly decomposed and stable with moderate C:N ratio (20:1 is good) so N does not become immobile in media
5. Easy to wet and retain enough moisture to reduce watering frequency Properties of an ideal propagation media
6. Sufficiently porous, excess water drains away, permits adequate penetration of O2 to roots
7. Free from pests: weeds, weed seeds, insects, nematodes, harmful bacteria, fungi and viruses
8. Low soluble salt levels (or else burns roots)
9. Capable of steam pasteurization, if needed, without harmful effects
10. High cation exchange capacity (CEC) for retention of nutrients, incorporated or applied to top of mix
11. pH between 5.5-6.5, micronutrients unavailable for root uptake at very high pH
12. Good buffering capacity (resistant to change pH), pH will not fluctuate much in containers
13. Consistent quality from batch to batch, reproducible
14. Readily available and economical
15. Create dark or opaque environment, reduce light penetration to cutting base, necessary for rooting

Factors involved in choosing a media mix to use for propagation

* Depends on species propagated
* Time of year cuttings taken: hardwood, semi-hardwood, softwood, herbaceous
* Type of cutting: leaf, leaf-bud, stem, root
* Propagation humidity system: fog, mist, flooding
* Cost of products in mix
* Availability and shipping charges
* For large nursery operations: best to buy bulk components and mix themselves
* For hobbyists, smaller operations: easier to buy pre-mixed media in bags

heat treatment via steam pasteurization

most effective way to rid media of pathogens using pasteurization

Process: steam heat set about 180ºF for 30 min., injected into covered bins or benches

* Does not kill all organisms, but majority of pathogens, nematodes and weed seeds killed
* Leaves behind beneficial organisms: mycorrhizal fungi, nitrifying bacteria, good bacteria, fungi, nematodes
* Helps avoid recontamination of harmful pathogens as some of the “good” organisms left behind to recolonize media
* Avoids ammonia gas, nitrite and manganese toxicity problems by using relatively lower temps

chemical fumigation

less effective method of eliminating media contaminants; used on moistened media

* Chemicals are highly selective for certain pests while steam is broader spectrum
* More practical for larger, field operations
* Chemicals very dangerous to both applicator and plants
* Must aerate media before use
* Reentry periods range from 2 days to 3 weeks
* Chemicals do not vaporize well at low \n temperatures
* No beneficial microorganisms remain to compete with harmful fungi or bacteria that might recolonize media

air-pruning propagation containers

* Creates better, more branched root systems
* Used on woody species
* Improves transplant survival
* Avoids circling roots in container as air pruned
* Expensive pots

cutting propagation

uses a portion of a stem, root, or leaf that is cut from the parent or stock plant and induced to form new adventitious roots and shoots by chemical, mechanical, and/or environmental manipulation.

why cutting propagation is used

* Used to clonally multiply many new plants, usually quicker than seed propagation
* The new rooted cutting is identical to the parent plant in most cases and is called a clone.
* Cuttings are used for many plants, both woody and herbaceous.
* Costs more than seed propagation as propagation facilities and mist are needed, but is cheaper than other methods such as tissue culture, grafting, layering, etc.
* However, resulting plants are genetically identical and uniform and can grow faster than seedlings

hardwood stem cutting

made from mature, woody, dormant (non-actively growing), firm wood after leaf abscission. The cutting cannot be snapped in half.

* Cuttings are usually taken from Nov. to late Feb. and are typically 6-8” long and ¼-1” in diameter
* Cuttings do not photosynthesize (no leaves) and must rely on stored carbohydrates and addition of external IBA/NAA, wounding is often needed
* Cuttings are taken during dormant season (late fall to late winter before budbreak) from wood produced the \n previous season
* They still take longer to root than other cuttings
* Popular method of propagated many woody species and some fruit crops

planting hardwood cuttings

* Cuttings can be directly stuck (planted) out in the field before the ground freezes in the fall and allowed to root during winter to spring. This technique is used in warmer climates or where snow cover is reliable.
* Takes longer to root in field due to cooler soil temperatures; dug following year from field and sold or left in field to use as rootstock for grafting or budding
* Can also be directly stuck (planted) out in the field in spring. These hardwood cuttings were taken the previous season are stored in high humidity cold storage (32-40°F) for months until spring.
* Can also be rooted in flats placed in a greenhouse in winter to allow for rooting indoors and eventual \n planting into containers or into the field in spring.

benefits of using hardwood cuttings

* One of the least expensive and easiest cutting propagation methods as no leaves are present
* May or may not need regular misting since leaves on deciduous species are not present, media stays moist
* Has larger amounts of stored carbohydrates that can result in heavier or more uniform rooting for some species
* Easy to prepare and store cuttings for months before sticking into flats for rooting or in field
* Not as perishable as semi-hardwood, softwood or herbaceous cuttings because no leaves are present
* Easier to ship over long distances even when rooted as no leaves are present yet (deciduous plants)

whip

a stem from an unbranched, long shoot from a young tree.

collar

he area of the stem where it meets the roots AND the area of a root where it meets the stem (same location)

polarity

the irreversible orientation inherent in stems and roots indicating which end is down (closest to crown/collar region of a plant) and which end is up (farthest from crown/collar of plant)

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* The polarity in shoots is opposite from polarity in roots.
* Roots will always form from the proximal (basal) portion of a stem, not at the distal (tip) end.
* Roots will always form from the distal (tip) portion of a root, not at the proximal (basal) end.
* You can tell proper polarity by looking for the buds on the twig and placement of leaf scars (buds always point upward and leaf scars located directly underneath a bud).
* Polarity will not change even when the cutting is flipped upside down in a flat, thus gravity does NOT affect polarity.

proximal (basal)

the area of the stem cutting that is closest to the plant’s roots or collar/crown AND the area of a root cutting that is \n closest to the plant’s stem collar.

distal (tip)

the area of the stem cutting that is closest to the plant’s tips or terminal bud AND the area of a root cutting that is farthest from the plant’s stem collar, i.e. the root tips

callus

undifferentiated scar tissue produced by the vascular cambium at the base of a cutting in response to wounding, for hardwood cuttings, callus is produced at the base of a cutting

wounding

the act of injuring a plant to achieve a specific goal

* induces a set of hormonal responses from the plant, which promotes root growth at the site of the wound.
* For cuttings, it is a vertical cut about 1-2” long made on either one side of the proximal end of a cutting or on both sides of a cutting if the species has a thicker stem.
* should penetrate through the bark just into the cambium (green tissue) and not deep into the xylem (white tissue).
* If you remove too much tissue, you remove the cambium and it will not work

why cuttings are wounded

1. Basal wounding is used in cuttings to expose the cambium to stimulate callusing and eventual adventitious root formation.
2. Rooting hormones are applied to the wounded, proximal end of a cutting due to a larger surface area on the cutting for auxin absorption than if non-wounded, i.e. more auxin is taken up by the proximal end than if non-wounded. The rooting hormone is in direct contact with the vascular cambium.
3. By exposing the cambium layer (undifferentiated cells) located right underneath the bark, the wounded area is exposed to auxin and will cause a response in the form of callus formation (undifferentiated cells). These callus cells will eventually differentiate and form new adventitious roots

plant hormones

naturally occurring organic compounds in a plant that are involved in the induction and regulation of growth and \n development.

* They are active at relatively small concentrations (μM - micro molar) and when applied to the plant endogenously or exogenously, it causes an effect
* Examples include auxin (IAA), cytokinin, gibberellins (GA), ethylene, abscisic acid (ABA) and other natural compounds within a plant.

naturally-occurring form of auxin

Indole-Acetic Acid (IAA)

It is not applied commercially as it breaks down in light and is not as effective as synthetic forms of auxin

plant growth regulators

synthetic chemicals used to stimulate rooting of cuttings.

These include all the hormones applied \n commercially and are produced by a manufacturer and applied to a plant by a propagator.

For auxin, PGRs available are IBA and NAA as well as K-salts of IBA

why cuttings are treated with root-promoting compounds like synthetic auxins

1. Increase the % of cuttings that form roots
2. Speed up root initiation from callus
3. Increase the number and quality of roots produced per cutting
4. Increase the uniformity of rooting, i.e. well-developed, uniform root system transplants better into larger pots

pros and cons of liquid auxin treatment

Pros

* Often more effective in penetrating the basal end of the cutting than talc, especially for hardwood cuttings
* More even and uniform application
* Taken up by cutting faster than talc

Cons

* If apply concentrated reagent grade IBA, need calculations for dilution in order to apply
* Molarity vs. ppm vs. % IBA, which to use
* Must store solution in dark, cool environment such as the refrigerator or shelf life is much shorter
* Risk of burning ends of cuttings, especially for softwood and herbaceous cuttings

pros and cons of talc auxin treatment

Pros

* Premixed, ready to use out of container
* No dilution or calculation needed
* Does not deteriorate over time
* Long shelf life
* Works well on softwood and herbaceous cuttings

Cons

* Tremendous dust from product, must wear mask over nose and mouth when pouring
* Non-uniform application compared to liquid
* Talc only stays on the surface of the cutting and does not penetrate like liquid
* Talc will rub off end of cutting if not moist at basal end or if dibble stick is not used first into the rooting media

semi-hardwood stem cuttings definition

taken from actively growing, woody deciduous, evergreen, or broad-leaved evergreens with partially lignified (mature) wood. These new shoots that were produced in the spring are no longer fleshy, but are semi-woody at the base, but are still actively growing

semi-hardwood cuttings details

* buds and leaves are present, and are thus photosynthesizing and transpiring
* cuttings are taken outdoors in late spring (end of June) to late summer (August) from wood produced that spring or in early fall (September) while still actively growing
* Cuttings have some flexibility, but can snap in half when bent severely
* Cuttings are ususally 3-6” long
* Cuttings are often treated with rooting hormone and sometimes wounded
* MUST be rooted under intermittent mist or fog system as they wilt easily

softwood stem cuttings definition

taken from soft, succulent, new spring growth of decidious and evergreen plants

softwood stem cuttings details

* plants are actively growing (not dormant) with leaves present
* cuttings have buds and leaves present, and thus are photosynthesizing and transpiring
* cuttings taken outdoors immediately after first flush of growth mid spring (May-June), but before semi-hardwood cuttings are taken
* cuttings are very flexible, bendable, and snap in half as the wood is not lignified yet
* cuttings root easier and faster than other wood cuttings
* cuttings usually 3-5” long
* cuttings can be treated with rooting hormone, but may not be needed (species dependent); wounding is rarely needed
* cuttings MUST be rooted under intermittent mist or fog system as they wilt easily

source of photosynthesis products or energy (carbs or sugars)

leaves, younger stems, to some extent younger bark produces carbs during the day and transports these sugars to sinks

sink of photosynthesis products or energy (carbs or sugars)

young, emerging leaves (because they are not fully capable of photosynthesis until they completely unfold), buds, roots, flowers, and fruit.

* Emerging leaves and flowers are energy demanding on a cutting and pull the sugars and water away from potential new roots

photosynthesis

* takes place inside chloroplasts inside a cell


* converts light energy from the sun or artificial lighting into energy that can be used to fuel growth and development of the plant as well as organisms that eat the plant


* sugars are transported to sinks
* 6CO2 + 6H2O --light→ C6H12O6 + 6 O2

respiration

* takes place inside the mitochondria inside a cell
* reaction is the exact reverse of photosynthesis, except it occurs with and without light
* glucose is broken down into water and carbon dioxide, releasing ATP in the process
* the energy is used by the plant for many biological processes

transpiration

* loss of water vapor through the stomates of the leaves and stems; can also occur in flowers and fruits
* water vapor is lost to the air via evaporation, helping to cool the plant and change the osmotic pressure of cells, allowing for mass flow of water and nutrients to flow from the root xylem to the shoot and leaf xylem
* lower rates are critical for the rooting of cuttings, maintained by mist or fog systems

herbaceous stem cuttings definition

taken from stems of succulent herbaceous plants with no woody tissue attached

herbaceous cuttings details

* can be taken any time of year if the plant is actively growing
* usually 3-5” long with no wounding or hormone treatment needed, but species dependent
* auxin can be used to increase uniformity in rooting and development of heavier root system, but not often needed
* cuttings dependent on production of internal auxin (IAA) and photosynthesis (production of new carbs)
* mist the cuttings often as they dry out quickly, except for cacti and some succulents
* rooting is usually rapid, with a high percentage of success
* distribution of vascular tissue in herbaceous plants is in vascular bundles rather than growth rings; this will affect the rooting response of the cuttings

herbaceous leaf cuttings definition

can be prepared using a whole leaf or leaf with a bud attached, but no stem

herbaceous leaf-bud cuttings details

* consist of leaf blase, petiole, and very short stem piece with attached axillary bud (node)
* can be taken any time of year, if plant is actively growing
* usually 1-1 1/2” long with no wounding or hormone treatment needed, but is species dependent
* auxin can be used to increase uniformity in rooting and development of heavier root system
* only adventitious roots need to form since bud is already present to produce a new shoot

herbaceous leaf cuttings details

* consist of a leaf blase of leaf blade and a petiole, but no bud or stem is attached
* can be taken any time of year, if actively growing
* length of the cutting is the length of the leaf, with no wounding or hormone treatment needed, but is species dependent
* auxin can be used to increase uniformity in rooting and development of heavier root system
* cytokinins can be used to induce bud formation on leaf cuttings
* both adventitious roots AND buds/shoots must be formed at the base of leaf cuttings
* the original leaf doesn’t become part of the new plant as it withers and dies as the new shoot grows
* only works for some plants
* a new plant forms at the base of the petiole
* adventitious roots from more readily than do adventitious buds

layering

development of adventitious roots on a stem while still attached to the parent plant

* layer = the rooted plant after detachment from the mother plant
* adventitious root formation stimulated by various treatments causing interruption in downward flow of carbohydrates, auxin, and other growth compounds
* key is elimination of light on stem where roots are to develop

advantages of layering

* useful for plants that naturally reproduce this way
* still attached to the parent plant so it has carbs, hormones, and water
* useful for propagating clones or difficult/impossible to root from cuttings plants as still attached to parent plant
* produces a large sized plant quickly vs. seed
* usually is successful and easy to do
* rejuvenation and invigoration of the parent plant = new shoots
* valuable for producing a small number of larger plants with minimum propagation facilities

disadvantages of layering

* expensive propagation method
* takes up considerable amount of space in field vs. seedlings or cuttings
* considerable hand labor needed, some mechanization possible on large scale
* must maintain healthy stock plants
* stock plants produce limited number of new plants
* stock plants take up a lot of space, hard to cultivate around them in nursery for weeds when being layered
* layers may be difficult to transplant due to smaller root system compared to top of plant, must acclimate first

factors affecting the regeneration of plants by layering

1. Stem wounding treatments
2. Light exclusion on stem
3. Continuous moisture
4. Aeration
5. Moderate temperatures in rooting zone
6. Physiological conditioning
7. Mineral nutrition of stock plant to layer
8. Rejuvenation
9. Use of root promoting compounds if needed

stem wounding treatments

cause interruption in downward translocation and accumulation of carbs and auxin just above girdle

* water isn’t interrupted as only cambium, phloem/bark removed at site of girdle - not the xylem

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girdling

cutting and removal of bark completely around stem

light exclusion on stem

blanching or etiolation

continuous moisture

layer underground must not dry out, cover up with moist media (not too wet or will rot)

aeration

around stem where roots form or will rot

moderate temperatures in rooting zone

if too cool, no roots, if too hot, will “cook” plants

physiological conditioning

stock plant growth stage

mineral nutrition of stock plant to layer

not N starved, but not excessive N either

rejuvenation

used in mound layering (stooling) by frequent cutting back of stock plant, sends up new shoots, cover base of new shoots with moist soil, then it roots

* stays in juvenile stage, easier to root

use of root promoting compounds, if needed

IBA, NAA

* often not needed as still attached to parent plant that is producing hormones (auxin)

forms of natural layering

tip layering

stolons

* runners (type of stolon)

rhizomes

suckers

watersprouts

offshoots (offsets or slips)

tip layering

* occurs naturally in trailing plants (brambles- black/raspberries)
* stem grows to ground, tip enters soil and forms roots, then new shoot arises
* can be done artificially, by buring the tip in soil, pin tip in place, cover with soil
* remove these new plants to propagate
* takes \~ 1 growing season to root, separate from parent plant, replant

stolons

* modified lateral stem produced by crown that grows horizontally above the ground
* main purpose is propagation
* can grow for great distances
* develops a new plant at one of its nodes
* can be done artificially by separating it from parent, planting it separately in soil
* ex- many grasses, redtwig dogwood, mint, ajuga

runners (type of stolon)

* occurs naturally in trailing plants with rosette/crown growth
* specialized stem that develops originally from the crown, then at the axil of a leaf at the new plantlet crown
* grows horizontally above the ground
* develops new plants at end or runner and eventually roots
* can be done artificially, separating from parent plant
* often form during long days and warm temperatures
* ex- strawberries, strawberry begonia, spider plant

rhizomes

specialized underground, horizontal stem

* primarily used for storage of carbs
* lateral, underground stem has nodes and internodes as well as roots on the bottom side
* stems arise in leaf-like sheath at bud/node on rhizome, forms its own roots
* when leaves and sheath eventually die, leaves scar on rhizome
* stems arise either terminally at tips of rhizomes or laterally along rhizome
* ex- snake plant, many perennials, lily-of-the-valley, some iris, bamboo, ginger, sugar cane, banana, grasses, some ferns, canna, some shrubs

suckers

* specialized vertical shoot arising from below ground from an adventitious buf on a root or from a bud at the crown base
* shoots arising from soil can come from rhizomes too
* suckers form their own roots
* often maintain juvenile phase
* can be done artificially by removal of sucker from tree base or via renewal pruning of shrubs
* ex- many bottomland tree species (green ash, silver maple, willows, poplars, boxelders), basswood, upland species like lilacs, sumacs, forsythia, pawpaw

watersprouts

* shoot arising from a latent bud on a stem that’s several years old growing above the ground
* found on the trunk and main branches and do NOT form roots
* often maintain juvenile phase and does not flower or fruit
* removed annually in commercial fruit orchards, landscapes; not used
* weak point of attachment, no branch collar or branch protection zone, breaks off leaving a wound on branch, produces no fruit
* ex- crabapples, apples, catalpa, honeylocust, magnolias, etc

offshoots

* type of lateral shoot or branch that develops from the base of the main stem of the parent plant
* offshoot forms independent crown and roots
* slow method of propagation
* also, from shortened, thickened stem or rosette-like plants
* can be done artificially be removal of offshoots from parent plant with a knife
* ex- pineapple, date palm, daffodil bulblets, daylily, hosta, palms

forms of artificial layering

* tip layering
* simple layering
* compound layering
* serpentine layering
* mound layering
* trench layering
* air layering

simple layering

* easy to do
* different from tip layering as shoot tip sticks out of the ground
* do in early spring or fall
* bend intact, one year old shoot from the parent plant to the ground, secure short, bent stem portion underground with pin or peg, cover with soil with portion of shoot tip remaining exposed to air
* may or may not need to girdle stem
* will produce adventitious roots at base of exposed shoot tip
* following year, sever from parent plant
* ex- filberts, lilacs, forsythia

compound layering

* similar to simple layering excpet the entire shoot with multiple nodes (not just the base of a tip) is held horizontally in a trench by pegs, then buried completely underground with moist soil
* numerous shoots develop at nodes along the buried stems
* these shoots will form adventitious roots
* ex- grapes

serpentine layering

* type of compound layer
* similar to compound layering except shoot is placed in trench alternating in and out of the soil, bend potion held horizontally by peg
* can wound first but not required
* node below ground will produce adventitious roots, other develops new shoots above ground
* get multiple plants to separate from parent plant
* used for propagating plants with long, flexible shoots
* ex- grapes, wisteria, clematis, philodendron

mound layering: stooling

* shoots on parent plant are cut back to base annually
* moist soil is mounded over emerging shoots with gradual mounding of more soil over shoots during the growing season
* only upper half of shoot tips stick out of soil
* lower shoot base eventually covered with 6-8” of soil
* adventitious roots are produced at base of new shoots in one growing season
* separate new rooted shoots from parent plant in dormant season, store rooted shoots in cooler or plant in field in spring
* some beds can be maintained for up to 20 years
* common practice for rooting apple, pear, cherry, filbert, ans pecans as difficult to root from cuttings

trench layering

* similar to mound layering
* Plants growing in nursery were originally planted on a 30-45 degree angle, establish for one year
* Second year, shoots from parent plant are placed horizontally into a soil trench, pegged down and covered with soil
* New shoots emerge from underground stem at nodes, these are then cut back and mounded with soil to induce etiolation
* New shoots grow longer and are covered with more soil during growing season to induce rooting along the stems
* Adventitious roots are produced at base of new shoots in one growing season
* Separate new rooted shoots from parent plant in dormant season, store rooted plants in cooler or plant in field in spring
* For some species that do not root with mound layering, trench layering breaks apical dominance as shoots from parent plant laid horizontally
* Used on apples, quince, mulberry, walnut, cherry

air layering

* Strip of bark removed all the way around stem using 3 cuts:
* Horizontal cut at top of girdle
* Horizontal cut at bottom of girdle, spaced 1” apart from top cut
* Vertical shallow cut between top and bottom cuts, slices it open
* Remove bark strip, avoid cutting into wood (xylem)


* Stops flow of carbs and auxin down the stem, accumulates at girdle, but water still transported
* Girdled stem portion is enclosed in moistened sphagnum moss or other material wrapped tightly around girdle
* Top of girdle should be in top 1/3 of sphagnum moss
* Completely wrap girdled area with sphagnum moss tightly in saran wrap and then aluminum foil
* Secure with twist ties or zip ties at top and bottom, want to hold in moisture, prevent from desiccation
* Adventitious roots eventually develop (2-3 months) in girdled area
* Sever rooted portion from parent plant at a node and pot up layered plant
* Use second year old wood in spring or summer
* Used on many houseplants such as rubber plant, weeping fig, X Fatshedera lizei, citrus, croton, large philodendron, dracaenas

crown division

* At plant crown, new shoots develop annually
* Divide (split off) these new shoots from the rest of the plant
* New shoots often contain some roots, if not treat as stem cutting
* Very common method of reproducing herbaceous perennials, hostas, ornamental grasses, some shrubs
* Dividing your perennials in early spring to increase vigor, avoid overcrowding and center of plants opening up with age and make new free plants
* Division necessary to propagate some variegated plants resulting from a chimera: variegated snake plant

geophytes

plants survive part of annual life cycle as a dormant, fleshy, underground structure; are perennial

types of geophytes

bulbs, corms, tubers, tuberous roots, tuberous stems, rhizomes, pseudobulbs (above ground for pseudobulbs ONLY)

geophyte functions

* underground structures function primarily for storage of water, nutrients, and carbs during adverse environmental conditions
* also function for propagation, as they self propagate

bulbs

specialized, underground storage organ consisting of a short, fleshy stem axis (basal plate) and roots or root primordia, axillary buds, and flower apices enclosed in thinkened, fleshy scales

* a series of modified leaves with no nodes
* mainly monocots
* spring or summer flowering or tender, winter flowering (Amaryllis, paperwhite Narcissus)
* tunicate (daffodils, tulips, etc) or non-tunicate (lilies)
* flower quality and size of flower(s) are directly related to size

tunicate (scaly) bulbs

type of bulb, outer bulb scales cover the bulb and are dry and membranous (tunic); inner, fleshy bulb scales are in concentric layers

* tunic: outer scales provide protection from drying out and mechanical injury
* tulips, daffodils, Alliums, hyacinth
* bulb goes dormant in summer

bulb scales

modified leaves, expanded, fleshy leaf base of a bulb that contains stored food

basal plate

short, thickened stem of a bulb

offshoots

latent shoot (small bulb) develops from main, mother bulb off of the basal plate

non-tunicate bulbs

bulb with no external, dry, papery, outer bulb scales; all bulb scales fleshy, separate easily

* scales separate easily from basal plate
* bulbs dry out faster; more sensitive to damage and desiccation
* must store in moist packing material
* all lilies, including Easter lily
* may have contractile roots that pull bulb deeper in soil
* bulb does NOT go dormant in late summer/fall, but loses flower shoots

bulblets

form in axil of internal bulb scales on non-tunicate bulbs, such as lilies, or form on the underground part of the lily stem or form on tunicate bulbs (hyacinth) after scooping, scoring

* often clustered together and have their own roots
* separate from mother bulb and plant, flower in a couple of years

bulbils

miniature aerial bulbs formed in axil of the stem and leaf, not underground

* used for propagation
* common with some lilies, especially Tiger lilies
* non tunicate bulbs only: lilies

tunicate bulbs (tulips only) life cycle

afrer flowering, outer bulb scales disintegrate partially or completely

* leave foliage intact after flowering to initiate offshoot formation (daughter bulbs) for rebloom next year
* may or may not perennialize, often have to replant every couple of years; may not come back after first year; too wet

tunicate bulbs (daffodils, grape hyacinth, Amaryllis, etc) life cycle

after flowering, bulb does NOT disintegrate

* leave foliage intact after flowering to trasnport carbs and water back to mother bulb, makes new offsets for next year’s bloom
* original mother bulb gets larger each year
* these bulbs perennialize well, plant only once, comes back each year

life cycle of non-tunicate bulbs

all lilies, including Easter lily

* after flowering, bulb does not disintegrate
* leave foliage and stem intact after flowering to transport carbs and water back to mother bulb and make new bulblets for next year’s bloom
* does not dieback quickly like daffodils, tulips, etc
* original mother bulb gets larger each year (produces more bulb scales
* these bulbs perennialize well, plant only once, comes back each year

methods to propagate bulbs

* seed (slow and not clonal, used for breeding)
* offshoot separation
* bulblet separation
* bulbil separation
* micropropagation
* stem or leaf cuttings
* scaling, twin-scaling, basal cuttage, scooping, scoring, chipping