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Learn about primary substrates used in production of container grown ornamentals, amendments, and how to monitor and manage inventory of substrates during production.

Bark as a primary substrate

Pine bark from either loblolly, short leaf, or slash pine is the primary component of substrates for container grown ornamentals in outdoor uncovered production in the southeastern U.S.

Technical Publications

  • Harrelson, T. et al. 2004. How do you manage fresh versus aged pine bark? Tested growth in 100% aged or fresh bark and added nutrients to accommodate nitrogen immobilization in fresh bark. Physical properties of fresh bark, with reduced container capacity and reduced available water compared to aged bark, may have been the cause of reduced growth. Growers might manage water differently if using fresh bark solely or as an amendment. T Harrelson, SL Warren, and TE Bilderback. SNA RESEARCH CONFERENCE 49:63-66 (2004)


  • Bilderback. Substrates for plants in big contaners. Dr. Bilderback discusses the use of pine bark for use in big containers. He provides a mini-overview of using pine bark and presents physical properties of various substrate combinations.
  • Bilderback Container soils and soilless media. Dr. Bilderback provides a comprehensive review of pine bark, physical properties, chemical properties, harvesting, storing, aging an almost all other facets of using pine bark and organic substrates as media for containers
Pine bark supplies Pine bark supplies
Pine bark based substrate Pine bark based substrate
Raw (unmixed) pine bark supply with mixed substrate in background containers Raw (unmixed) pine bark supply with mixed substrate in background containers
Substrate mixer and loader Substrate mixer and loader
Substrate being transported Substrate being transported by tractor trailers


Alternatives or amendments to bark

Technical Publications

Extension Publications

  • Sherman, R. 1999. Large scale composting. Comprehensive guide to design, layout, scientific underpinning of composting, feedstock and its carbon nitrogen ratio, permitting, and testing. Rhonda Sherman, Extension Waste Management Specialist, NC State Extension. AG-593.
  • Sherman, R. 2000. Community backyard composting programs. Getting started on a small scale to reuse community waste products. Rhonda Sherman, Extension Solid Waste Specialist, NC State Extension. AG-599.
  • Bass et al 1992. Composting: A guide to managing organic yard wastes. Start composting in your back yard with this primer for the task. Bass, L, TE Bilderback, and MA Powell. NC State Extension. 1992. AG-467. RETIRED.


  • Jackson BE 2009 Back to the grind. A great overview of the properties, effects on growth, and challenges to using a wood-based substrate on ornamental crops. Pine tree based substrates encourages prolific root growth in container plants. Jackson BE NMPRo 28-34.
  • Jackson 2009. A suitable substrate alternative. A great history, description and vision of the use of wood-based substrates in the nursery industry. Summarizes many studies using the substrate to grow woody ornamentals. Jackson B American Nurseryman pp. 28-33 (Sept 2009).
  • Bilderback et al 2007. Non-organic amendments can extend media lifeInorganic components include perlite, pumice, coarse sand, industrial clays, concrete block particles and plastics like those contained in municipal garbage. TE Bilderback, JS Owen Jr., SL Warren and JP Albano. NMPRO • Nursery Management & Production pp. 37-42.
  • Bilderback TE. Fluff, stuff and any other components added to substrate. Dr Bilderback summarizes over a decade of research and investigation into using various components as amendments to pine based substrates and discusses measuring the physical properties to see if they can be used for growing ornamental plants. A semi-annotated PowerPoint as PDF.
  • Bilderback and Warren. Get Physical with Fluff®. Effects of amending pine bark with garbage. Highlights research from NC State with municipal solid waste.
  • Yao 2010. Whole Tree: A More Sustainable, Environmentally Friendly Substrate. Update article of a nursery using Whole Tree as a substrate. Agriculture Research Service August 2010. pp.28-29.
Wholetree substrate Wholetree substrate delivered to a nursery.
Sand used to increase mass of substrates Sand used to increase mass of substrates
WastAway substrate WastAway substrate [Municipal solid waste compost (MSWC)
WastAway substrate WastAway substrate (close-up) [Municipal solid waste compost (MSWC)
Forest harvest debris being transported and processed for use as substrate Forest harvest debris being transported and processed for use as substrate


Physical and chemical properties

Learn the most important components to determining if a substrate is correct for use in your nursery. The physical properties, like total porosity, container capacity (water holding capacity), and air filled porosity, balance pore space for roots, air exchange and water for growth. Chemical properties, like pH and electrical conductivity, determine which nutrients are available, how tightly the substrate holds them, and if they are in high or low quantity. Moreover, when substrates are amended with organic or inorganic components, both physical and chemical properties change to affect plant growth. Make sure any new substrates are tested for these metrics to see how it might affect growth.

Technical Publications

  • Bilderback et al 2005. Healthy substrates need physicals too. Dr. Bilderback and colleagues present physical property guidelines for many pine bark-based substrates with amendments. They discuss challenges to adding amendments, volumes of those amendments, and how physical properties can change from beginning to end of production in containers. TE Bilderback, SL Warren, JS Owen, Jr., and JP Albano. HortTechnology 15:747-751.
  • Bilderback 2009. A nursery-friendly method for measuring air filled porosity of container substrates. The description for construction of a “home built” porometer apparatus to measure air-filled porosity (AFP) is described. This is an excellent device to monitor bark supplied between distributors, after new amendments are incorporated, or if a long time has lapsed since the last time bark was obtained from a supplier. See photos section for examples of it in use. T Bilderback Research Conference 54:212-215 (2009).
  • Cooke et al 2004. Physical property measurements in container substrates: a field quantification strategy. Determining drained pore space (air space), using the simple procedure outlined here can provide useful insight into how to manage irrigation of crops having drainage or aeration problems and possibly into diagnosis of how to make changes to avoid future problems. A Cooke, T Bilderback, and M Lorscheider. SNA RESEARCH CONFERENCE 49:102-104 (2004).
  • Buamsch, MG et al. 2007. Chemical and physical properties of Douglas Fir Bark relevant to production of container plants. Tested various properties of Douglas fir bark and found that properties differ less to age than to bark source. M. Gabriela Buamscha, JE Altland, DM Sullivan, DA Horneck, J Cassidy. HORTSCIENCE 42(5):1281–1286. 2007.


  • Bilderback. Getting physical with potting mixes. Dr. Bilderback annotates a power point presentation as pdf document about measuring physical properties of substrates and how that is affected by amendments, time, and growing methods.
Fill cylinders with substrate Fill cylinders with substrate
Fill cylinders with substrate Fill cylinders to the top with substrate and tamp lightly. Repeat 3 times.
Filling cylinders with substrate Filling cylinders with substrate
saturating substrate with water Fill bucket with water to top of cylinder to fully saturate substrate
saturated substrate When water beads at top fo substrate after 15-30 minutes, pore spaces are saturated
removing from bucket After substrate is saturated, plug bottom holes with hand to remove from bucket
draining excess water Let water that has filled pore spaces drain into bucket
water collected in bucket Water in pore spaces drains from cylinder into bucket for measurement
water collected in bucket Water from pore spaces drains into bucket
measuring volume of leachate Measure volume of leachate using a graduated cylinder or something similar
measuring volume of leachate Measuring the volume that leached from pore spaces
repeating process Repeat the process several times to get an average air filled porosity


Manage Inventory

Learn how to manage inventory of primary substrate supplies by reading these Extension Publications.

Extension Publications

  • Bilderback. Bark and roll over. Dr, Bilderback discusses media management while its on your nursery and not in containers.
  • Bilderback, T. Managing container substrates. How organic potting components are stored and managed can have great effects on the chemical and physical properties of the container mix. Dr. Bilderback addresses the importance of these challenges. NC State University.
  • Bilderback T., Pine bark storage and handling. An overview, provided Dr. Bilderback, of the process to maintain high quality, weed and pathogen free substrate supplies prior to potting. NC State University.

Sourcing Substrates

  • Substrate, mulch and pine bark suppliers-revised version 2012. Mention of trademark, proprietary product, or vendor does not constitute a guarantee or warranty of the product by the authors, NC State University, or the Department of Horticultural Science, and does not imply its approval to the exclusion of other products and vendors that also may be suitable. To be added as a supplier e-mail and provide a name and phone number for contact.
substrate piles being irrigated Irrigating substrate piles to keep its wetting ability consistent while waiting to be used in potting
substrate piles being irrigated Irrigating substrate piles to keep its wetting ability consistent throughout pile
Substrate is stored at highest point in nursery and on an impermeable surface to prevent pathogen infestation Substrate is stored at highest point in nursery and on an impermeable surface to prevent pathogen infestation


Written By

Brandon Hopper, N.C. Cooperative ExtensionBrandon HopperBusiness and Technology Application Technician Call Brandon Email Brandon Horticultural Science
NC State Extension, NC State University
Page Last Updated: 1 year ago
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