herbaceous 2.0

PLANT GROWTH REGULATORS (PGRs)

• Auxins - Promote rooting and shoot elongation

• Gibberellins (GA) - Stem elongation, flower/fruit development

• Cytokinins - Cell division, delay senescence

• Ethylene Generators - Flower abortion, ripening, branching (e.g., Florel/Pistill = Ethephon)

• Anti-GA/Growth Inhibitors - Reduce elongation, compact growth (e.g., Bonzi, A-Rest)

PGR Strategy by Crop Stage

• Early: Spray/sprench to reduce initial stretch

• Mid-Crop: Drench low to moderate rate

• Pre-shipping: Stronger drench (not spray)

• Hanging Baskets: Spray early, drench late

PGR Calculations - Key Notes

• 1% = 10,000 ppm

• ppm = (mg/L) = (ml product - ppm of stock) / L solution

• Use conversion: 1 oz = 29.57 ml; 1 gal = 3.79 L

GROWING ON & TRANSPLANTING

• Watering: Moist after transplant - Moderate - Dry at finish

• Fertilizer: Low ammonium, high nitrate (e.g., 13-2-13)

• Avoid high P (e.g., 20-20-20) except as a starter

FACTORS AFFECTING FLOWERING

• Cold Treatment (6-10 wks at 40-F)

• Photoperiod - Long days or night interruption

• Light Intensity - High for compact growth

• Juvenility - Must reach size before flowering response

PERENNIALS PRODUCTION

• Herbaceous: Die back in winter, regrow from roots

• Cold-requiring: e.g., Columbine, Dicentra

• Dormant types: e.g., Freesia - dormant under drought/heat

• Production: Pot in spring/fall, overwinter, sell spring

LABOR & COST ANALYSIS

• Labor Phases: Potting, Care, Harvest

• Variable Costs: Fertilizer, plugs, tags, hourly labor

• Fixed Costs: Depreciation, interest, insurance, taxes

• Overhead Example: $0.20/sq ft/wk - 1.69 ft- - 4 wks = $1.35/flat

SPACING, HANGING BASKETS & MIXED PLANTERS

• Spacing: Improves airflow, reduces disease

• Hanging Baskets: Spray early, drench mid-late

• Mixed Planters: Treat most vigorous plant, use liner dips

PGRs

Class	Function

Auxins

Rooting, apical dominance

Gibberellins (GA)

Stem elongation, flower/fruit development

Cytokinins

Cell division, delay senescence

Ethylene Generators

Flower abortion, ripening, branching (Florel/Pistill = Ethephon)

Anti-GA / Growth Inhibitors

Reduce elongation, compact growth (e.g., Bonzi, A-Rest)

Common Anti- GA active ingredients

Trade Name	Common Name	Class	Use Notes

Bonzi

Paclobutrazol

Triazole

Strong, not root-mobile in bark mediums

A-Rest

Ancymidol

Pyrimidine

Only one approved for subirrigation

Sumagic

Uniconazole

Triazole

Strongest anti-GA, effective at low rates

Cycocel

Chlormequat chloride

Quaternary

Common for geraniums, phytotoxic at high spray volumes

B-Nine/Dazide 85

Daminozide

GA mimic

Short-lived, safe, only used as foliar spray

application methods

• Foliar Spray – Apply 0.5 gal/100 sq ft for uniformity

• Drench – Long-lasting, more exact, suited for final shaping

• Sprench – High-volume spray for plug trays (2–4× normal volume)

• Dip – Consistent exposure for liners (e.g., chrysanthemum shoots)

• Media Spray – Applied to medium before planting

• Seed Coating – (e.g., A-Rest on pelleted Wave Petunia seed)

PGR strategy by crop stage

Stage	Best PGR Strategy

Early after transplant

Spray or sprench low rate for early stretch control

Mid-crop

Drench low to moderate to tone plant

Just before shipping

Drench stronger rates to hold, not foliar spray

Hanging baskets

Apply early, then late; NO foliar late—interferes with flowering

PGR calculations (must know)

1% = 10,000 ppm
ppm = (mg/L) = (ml product × ppm of stock) / L final solution
Cost = ($/ml) × ml used
Know how to convert: oz ↔ ml (1 oz = 29.5735 ml), gal ↔ L (1 gal = 3.79 L)

watering strategy

Stage	Watering Practice

After Transplanting

Moist media to promote root establishment

Establishment Phase

Moderate drying between irrigations to stimulate rooting

Finishing Phase

Drier cycles; restrict water slightly for toning and compact growth

fertilizer strategy

• Avoid high ammonium (NH₄⁺) → causes soft, stretched growth

• Use nitrate (NO₃⁻) based formulas → 13-2-13, 15-5-15 for compact plants

• Avoid high phosphorus (e.g., 20-20-20) except as a starter charge

common mistakes to avoid

• Overwatering after transplant → root rot, poor establishment

• Applying PGRs too early → insufficient shoot presence

• Skipping water before drenches → uneven uptake

flowering induction triggers

• Cold Treatment (Vernalization): Most perennials require 6–10 weeks @ 40°F

• Photoperiod: Many require Long Days (LD; >14 hours or night break)

• Light Intensity: Increases quality and flowering; avoid excessive shading

developmental considerations

• Juvenility: Must reach certain size before flowering response is possible

• Reproductive Vegetativeness: Propagules from clones may flower sooner

perennial production

Type	Description

Herbaceous Perennial

Dies back in winter, regrows from roots

Cold-requiring Species

Columbine, Dicentra – need cold to flower

Dormant Types

Freesia, some coreopsis – induced by drought or heat

scheduling- PP

• Spring Sales: Pot cooled liners in March, sell by May–June

• Overwintering: Pot in late summer/fall, overwinter, sell next spring

• Bulk Up Cycle: Pot → Grow On → Overwinter → Sell

cooling and forcing- PP

Factor	Warm Forcing	Cool Forcing

Temp

60–68°F

40–50°F

Fertilizer

100–200 ppm N

50–100 ppm N

Benefit

Faster, stretchier

Slower, sturdier

labor categories (greenhouse operations)

Category	Activities

Potting

Mix media, fill pots, transplant, label

Care as Needed

Watering, fertilizing, PGRs, pinching, spacing

Harvest

Grooming, packing, moving, staging, shipping

cost types

Variable Costs	Fixed Costs (DIRTI)

Pots, plugs, tags

Depreciation, Interest, Repairs, Taxes, Insurance

Fertilizer, chemicals

Salaries, structure costs

Labor

Equipment maintenance

overhead calculation example

you have 1000 flats on 1690 sq ft of bench for 4 weeks

overhead rate= $0.20 sqft/wk

total 1690 sq ft x $0.20 × 4 = $135.20

per flat = $135.20/1000 = $0.135 per flat

spacing consideration

• Increases air flow → reduces disease

• Allows better light penetration → uniform growth

• Avoid crowding especially late in the crop cycle

hanging basket PGR strategy

Timing	Application

Early (1–3 weeks)

Spray or liner dip

Mid Crop

Low-rate drench

Late Crop

Stronger drench; avoid spray

mixed planters consideration

• Apply PGR to most vigorous component (e.g., calibrachoa in combo)

• Uniform PGRs can distort mixed combos → treat selectively if possible

• Early shaping → liner dips preferred

Environmental conditions influencing FBI 

• Cold treatment 

• Long day photoperiod

Variable cost (change with production volume):

1. Pots: more plants = more pots 

2. Rooted cuttings or seeds: directly tied to number of plants produced 

3. Fertilizer: applied as needed based on plant numbers 

4. Plant growth regulators (PGRs)/pesticides: cost scales with treated area 

5. Direct labor (sticking cuttings, transplanting, pinching, watering): labor hours increase with crop volume 

Fixed Costs (remain stable regardless of production volume):

1. Depreciation on equipment: fixed annual expense, whether producing 10 or 10000 flats 

2. Greenhouse structure and maintenance: building cost is incurred regardless of use 

3. Salaries of salaried staff (managers, accountants): paid consistently 

4. Insurance: annual premium unaffected by crop load 

5. Property taxes: statice overhead cost based on land/building value

photoperiod

• photosynthesis at maximum at 3500 f.c., 14 mol light per day

• supplemental light on cloudy days to keep plugs compact, build density, promote branching

• manipulation of photoperiod for sensitive species can hasten or delay flowering

photoperiod- short day

• facultative: flowers more quickly under SD and with fewer nodes below first flower

  • zinnia hybrida ‘Profusion’

  • celosia plumosa ‘Kimono’

  • cosmos bipinnatus ‘Sensation White’

• obligate: SD required for FBI

  • celosia plumosa ‘Flamingo Feather’

  • cosmos sulphureus

photoperiod- long day

• facultative: flowers more quickly under LD and with fewer nodes below the first flower

  • ageratum houstonianum ‘Blue Danube’

  • calendula officinalis ‘Calypso’

  • dianthis chinesis ‘Ideal Cherry Picotee’

• Obligate: LD required for FBI

  • labelia erinus ‘Crystal Palace’

  • Petunia ‘Wave Purple’

photo-accumulation

day neutral

• FBI unaffected by daylength but light intensity and temperature influence flowering

  • begonia semperflorens

  • impatiens wallerana

  • nicotiana alata

  • tagetes potula

  • zinnia angustifolia

facultative irradiance response

• species exhibiting a facultative irradiance response flower faster because the juvenile stage of development is shortened under high light levels

stress

• FBI faster with some species when water stressed and or nutrient stressed

• death row flowers