Growing in Containers

Charles Eckman

USDA Forest Service

J.W. Toumey Nursery

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2021 University of Minnesota Extension Northeast Regional Sustainable Development Partnership

Your computer, somewhere, anywhere • 23 September 2020

J.W. Toumey Nursery

• Established 1935
• Provides reforestation stock to the Great Lakes Region National Forests
• Bare root and container

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Seedling development in nurseries

Outline

• Resources
• Target Plant Concept
• Containers & Growing Media
• Seed
• Background on phases
• Establishment phase
• Rapid growth phase
• Hardening phase
• Questions and answers

Resources (rngr.net)

USDA Agricultural Handbooks:

• The Container Tree Nursery Manuals, Volume 1-7, AH-674
• https://rngr.net/publications/tribal-nursery-manual
• The Nursery Manual for Native Plants: A Guide for Tribal Nurseries, AH-730
• Tropical Nursery Manual: A Guide to Starting and Operating a Nursery for Native and Traditional Plants, AH-732

Resources (rngr.net)

• Native Plant Network
• Propagation Protocols

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• The Woody Plant Seed Manual
• Agriculture Handbook 727

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• Manual of Woody Landscape Plants: Micheal A. Dirr
• Western Forestry and Conservation Association Webinars
• https://westernforestry.org/upcoming-conferences/2020-north-american-forest-and-conservation-nursery-technology-webinar-series

Target Plant Concept

1. Project objectives?

2. Limiting factors on out planting site?

3. Species and genetic source?

• Local adaptation, genetic diversity

4. Stock type?

• What type of plant material will meet project objectives?

5. Out planting tools and techniques?

6. Out planting window?

https://www.fs.fed.us/rm/pubs_series/wo/wo_ah730.pdf

Growing Media

• One of most important considerations
• Substance through which roots grow and extract water and nutrients
• Plants growing in containers have limited amount of growing media
• Biological and operational considerations

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• Physical Properties
• Water holding capacity
• Aeration
• Porosity
• Bulk density (weight per volume)
• Chemical Properties
• Fertility
• pH
• CEC (ability of media to chemically hold positively charged ions) Reflects nutrient storage capacity.

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Container Considerations:

• Choice depends on:
• Root system morphology
• Target plant criteria
• Economics & availability

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• Root Quality: Dependent on species root system

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• Shorter containers
• Better for shallow, fibrous root systems (forbs)

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• Taller containers
• Better for species with long tap roots (oaks)

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• Wider containers
• Better for species with multiple, thick fleshy roots

Containers Considerations

• In general plants growing at closer spacing grow taller and have a smaller root collar diameter

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• Large broad-leaved species grow best at low density
• Smaller leaved & needle species can grow at a higher density

• Operational & Economic
• Durability & reusability
• Handling
• Ability to check roots
• Ability to cull & consolidate

Seed

• Essential to know and understand the seed dormancy type: Understand ecology of species
• Nondormant
• Dormant
• Physical
• Physical & physiological
• Morphological
• Check Native Plant Propagation Protocol Database

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Seed Storage: orthodox/recalcitrant seed

• Orthodox
• Survive drying and freezing

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• Recalcitrant
• Do not survive drying or freezing during ex situ storage.
• Often best to sow immediately

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• Red oak
• Seed dormancy
• Germinate in spring
• If not fall sown will need stratification

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• White Oak
• No seed dormancy
• Germinate in the fall

Seed

• Determine quality of seed
• Test
• Seed viability: estimate of potential for seed to germ & grow

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• Seed germination: measures actual germination % and rate

How many seeds per cell?�Source: Nursery Manual for Native plants, Chapter 8, USDA Forest Service

Other Sow Calculation Resources

The Container Nursery Manual, Volume 6, Chapter 6.2.8.1

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Seed Handling Guide: Ministry of Forestry, Province of B.C.

https://www2.gov.bc.ca/assets/gov/farming-natural-resources-and-industry/forestry/tree-seed/tree-seed-publications/seed_handling_guidebook_hi.pdf

Seedling development in nurseries

Why manage for growth stages?

• Plant needs are different
• Planning
• Protocol development
• Management timelines
• Increased efficiencies
• Water, fertilizer, labor, atmospheric conditions
• Seedling quality
• Outplanting success

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Seedling development in nurseries

The Establishment Phase

Definition:

From germination through emergence and formation of true leaves

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Duration:

Typically 14 to 21 days for germination; 4 to 8 weeks for early growth

The Establishment Phase

Objectives:

• Fill containers uniformly
• Maximize uniform germination
• Maximize survival
• Minimize damping-off

The Establishment Phase

Special Needs:

• Protect from weather and pests
• Atmospheric environment
• Temperature
• Moisture
• Light
• Edaphic environment
• Proper irrigation
• Moist, not wet
• No or low fertilizer inputs

Tropical Nursery Manual – Photo: Douglass Jacobs

The Establishment Phase

Germination:

• Frequent Light Misting
• Some species may benefit from fogging
• Must be done carefully to ensure even moist environment around seeds
• Excessive water can lead to pre and post emergent damping off disease!

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Root elongation & true leaf development:

• Monitor root development to gauge frequency and duration of irrigation
• Use visual/ weight methods to determine when to irrigate
• Young seedling roots elongate through media but don’t have many secondary roots at this stage

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Determining When to Irrigate

The Establishment Phase

Adjusting Fertigation Regimes for Plant Growth Phases

Nursery Manual for Native Plants

The Establishment Phase

Labor:

• Monitor germination
• Thinning
• Re-sow and transplant if necessary
• Scout for pests and diseases

Itasca Greenhouse

The Rapid Growth Phase

Definition:

From emergence of true leaves to when seedling approaches target size. Rapid increase in size, particularly in terminal shoot

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Duration:

Varies widely, typically about 10 to 20 weeks

Tropical Nursery Manual – Photo: Douglass Jacobs

The Rapid Growth Phase

Objectives:

• Minimize stress
• Encourage shoot growth
• Maintain environmental factors near optimum levels
• Monitor as seedling approaches target height and roots fully occupy container

Photos: Jessie Godfrey

The Rapid Growth Phase

Special Needs:

• Protect from stress
• Atmospheric environment
• Warm temperatures
• Adequate light
• Photoperiod adjustment
• Edaphic environment
• Proper irrigation
• Limit moisture stress
• Adequate fertilizer
• Amount and type

NH₄⁺

NO₃^-

NH₄NO₃

Hieracium scouleri var. nudicaule (Hairy Albert)

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The Rapid Growth Phase

Adjusting Fertigation Regimes for Plant Growth Phases

Nursery Manual for Native Plants

The Rapid Growth Phase

Rapid Growth Phase:

• Typically, double the water use of the establishment phase
• Great variability among species
• Foliar interception becomes an issue as the leaf canopy develops
• Frequent leachings required with fertigation to prevent salt build-up

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Determining When to Irrigate

The Rapid Growth Phase

Labor:

• Monitor environment
• Adjust culture to avoid excessive shoot height
• Modify crop density to encourage good development
• Scout for pests and diseases

Tropical Nursery Manual – Tom Landis

The Hardening Phase

Definition:

Energy diverted from shoot to root growth; seedling reaches target height and stem diameter; seedling is conditioned to endure stress

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Duration:

Varies widely, normally from 4 to 12 weeks

Tropical Nursery Manual – Photo: Douglass Jacobs

A bit more on seedling hardening

Container Tree Nursery Manuel (Vol 6, Seedling Propagation, 1998)

• Most important period of seedling culture
• Preparation for stressful post-nursery conditions
• Lifting/packing
• Long-term storage (cooler/freezer)
• Long distance shipping
• Harsh outplanting environments
• No post-planting care

The Hardening Phase

Objectives:

• Manipulate seedling morphology
• Slow shoot growth
• Increase root and stem diameter growth
• Acclimate to outplanting environment
• Develop stress resistance for handling, storing, and shipping
• Fortify for survival after outplanting

Hardiness objectives

• Fortify seedling for survival and growth after outplanting
• Mineral nutrition
• Seedling balance (R:S)
• Water stress
• Slow shoot growth
• Leaf morphology adjustment
• “Physiological adjustment”
• Resist holding over

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Thick leaf cuticle

Hardiness scheduling

Typically 2 time periods

• Dormancy induction
• Species dependent
• Photoperiod, temperature, irrigation, fertilization
• Stress conditioning
• Photoperiod, temperature, irrigation, fertilization
• Mostly related to cold hardiness
• Drought?

from Lavender 1984

The Hardening Phase

Special Needs:

• Induce moderate moisture stress
• Reduce fertilization rates and change mineral nutrient ratios
• Progressively expose to sun equivalent of outplanting conditions (full sun or partial shade)
• Expose to ambient temperatures and humidity

Thick leaf cuticle

The Hardening Phase

Adjusting Fertigation Regimes for Plant Growth Phases

Nursery Manual for Native Plants

The Hardening Phase

Hardening Phase:

• Decreasing irrigation frequency to induce hardening
• Must be done correctly
• Must adapt deficit irrigation practices based on species grown

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Determining When to Irrigate

The Hardening Phase

Labor:

• Monitor crops and environment carefully
• Deliver crops to clients in a timely fashion to avoid problems with holdover stock
• Prepare crops for cold/freezer storage
• Scout for pests and diseases

Photo: Tara Luna

Botrytis blight

Photo: Thomas Landis

Some notes on seedling conditioning

New research on seedling conditioning for dry outplanting conditions:

Sloan, Burney, Pinto. 2020. Drought-conditioning of quaking aspen (Populus tremuloides Michx.) seedlings suring nursery production modifies seedling anatomy and physiology. Frontiers in Plant Science 11, 557894.

The future of drought conditioning

Plastic pine (Pinus plasticus )

Pub shrub (Shrubus intoxicatus)

Thank You!

• Charles Eckman
• USDA Forest Service
• charles.t.eckman@usda.gov
• rngr.net

Acknowledgements:

Jeremiah R Pinto

Tom Landis

R Kasten Dumroese

Owen Burney

Joshua Sloan

Many others!

Resources (rngr.net)

USDA Agricultural Handbooks:

• The Container Tree Nursery Manual, Volume 1-7, AH-674
• The Nursery Manual for Native Plants: A Guide for Tribal Nurseries, AH-730
• Tropical Nursery Manual: A Guide to Starting and Operating a Nursery for Native and Traditional Plants, AH-732