Cutting propagation is the most widely used method for cloning nursery and floriculture crops. Some of the factors that affect successful cutting propagation include stock plant quality, timing of propagation, propagation environment, container size, rooting substrate, and auxin treatment. A proper balance of air space and container capacity are critical for healthy root development, so the combined effects of propagation environment (mist application volume and frequency) and container size must be well understood when selecting a propagation substrate (Threadgill et al., 1985).
Sphagnum PM, PB, perlite, and vermiculite are commonly used as substrates for propagation, either individually or in combination at various proportions. The high transportation costs and variable annual harvest of Canadian PM have negatively impacted greenhouse crop producers in the United States (Fain et al., 2008; Harrison, 2011). Before the housing market decline of the late 2000s, nursery crop producers experienced a reduction in PB supplies and a rise in cost due to both PB’s use as boiler fuel and a decline in the timber market (Lu et al., 2006). Although PB supplies have rebounded in recent years, the long-term availability of PB will remain a concern. Although many alternative substrates have been used to produce quality container-grown crops, it has not been determined if such substrates are suitable for propagation. Ideally, an alternative substrate component should be cost effective, sustainable, and regionally available.
Alternative substrates should be evaluated within a propagation environment before extensive use. Offord et al. (1998) demonstrated coconut coir was a suitable alternative to PM for propagation of sydney bush pea (Pultenaea parviflora). Shah et al. (2006) reported silt and sawdust as acceptable substrates for long-leaf fig (Ficus binnendijkii ‘Amstel Queen’) cutting propagation, yet a traditional substrate was not included for comparison. Composts derived from a variety of materials have also been used for cutting propagation. Cuttings of three foliage plant species had similar root development in composts mixed with PM or PB and in a standard substrate (Chen et al., 2003). Chong (1999) noted composted municipal waste blended with perlite was a satisfactory substrate for cutting propagation of several woody plant species.
Wood-based substrates have been identified as acceptable supplements or replacements for PM and PB in crop production. Wood-based materials derived from pine trees are readily available throughout the southeastern United States and include clean chip residual (bark, limbs, and needles), processed whole pine trees (wood, bark, limbs, and needles), and chipped pine logs (wood and bark). These substrates have been extensively evaluated for greenhouse and nursery crop production (Boyer et al., 2008; Fain et al., 2008; Jackson et al., 2009; Wright and Browder, 2005). Although crops grown in these substrates commonly required additional fertilizer when compared with those grown in traditional substrates (Fain et al., 2008; Jackson et al., 2008; Wright et al., 2008), nutrient and water availability issues can be readily managed during crop production.
The suitability of loblolly pine wood-based substrates for cutting propagation has not been investigated. Demonstrating the versatility of these substrates is essential to expanding their commercial availability and use. The objective of the current experiments was to evaluate processed whole pine tree as a rooting substrate for stem cutting propagation of ornamental crops.
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