GROUND DEMOLITION WOOD 



IS NOT WORTHY OF BEING CALLED MULCH 



Francis R. Gouin 



TODAY'S crushing and grinding 

 equipment combined with magnetic 

 belts now make it possible to convert 

 used pallets, discarded wooden furni- 

 ture, tree trunks and condemned 

 wooden buildings into woodchips. 

 Whole-tree chippers are also being 

 used to convert lumbering waste as 

 well as dead and dying trees, many 

 infested with diseases and insects, 

 into wood-chips. The resulting chips 

 are sometimes marketed as mulch 

 immediately after processing, or 

 stacked into large piles for aging or 

 colored by mixing with either pine or 

 hardwood bark mulch for several 

 weeks. The fines resulting from 

 screening are in some instances sold 

 as soil amendments to unsuspecting 

 buyers. 



This latest effort in recycling is 

 attracting many new entrepreneurs 

 and creating numerous horticultural 

 problems. Every "Tom, Dick and 

 Harry" in waste wood recovery is 

 looking at the mulch market to in- 

 crease their profits. Since they al- 

 ready collect tipping fees to allow the 

 wood to be dumped on their property 

 and to pay for grinding, selling the 

 ground wood as mulch is clear profit. 

 To these individuals, mulch is wood 

 waste that is spread on the ground. 

 They are not aware that quality bark 

 mulch consists mostly of lignatious 

 materials that decompose slowly. 

 Woodchips from demolition, trees, 

 branches and tree trunks consist 

 mostly of cellulose and starches that 

 must undergo decomposition through 

 composting before they can be used. 

 To the unsuspecting buyer, it may 

 look like great stuff at a great price. 

 Even the experienced landscape 

 contractors are buying it because 

 it's cheap. 



The end result from this new 

 recycling effort is a glut of nitrogen 

 (N) -robbing, disease and insect- 

 infested wood waste, sometimes 

 loaded with alcohol and acetic acid. 

 When applied as a mulch around 

 young trees, shrubs, herbaceous 

 perennials and annuals, it will rob N 

 from plants, causing them to become 

 stunted with yellow-green bottom 



leaves, often dropping prematurely. If 

 the material has been stored in large 

 piles, it is not uncommon for the 

 wood waste to accumulate sufficient 

 amounts of alcohol and/or acetic acid 

 to kill plants. 



When ground demolition wood 

 and wood chips are used as a mulch, 

 it controls weeds by suffocation and 

 by starving them from N. However, it 

 will also starve the desired landscape 

 plants for N at the same time. Newly- 

 planted plants and shallow-rooted 

 species will be those most vulnerable 

 to injury. 



The problem with using ground 

 demolition wood and wood chips as a 

 mulch is due to an imbalance in the 

 carbon/nitrogen (C/N of the materi- 

 als. For demolition wood, the C/N 

 ratio is between 700/1 and 800/1 

 while the C/N for wood chips from a 

 branch, tree trunk, and whole-tree 

 chipper is between 200/1 and 300/1. 

 Most of the carbon in both of these 

 sources is in the form of cellulose and 

 starches. These carbon sources are 

 very different from those of pine bark 

 or well-composted hardwood barks 

 which consist mostly of lignins. Al- 

 though lignites are a source of carbon, 

 they are resistant to decomposition. 

 Their rate of decomposition is so 

 slow that it does not compete with 

 plant roots for N. Therefore, to uti- 

 liie ground demolition wood and 

 woodchips as a mulch, their C/N 

 ratio must be reduced to 60/1 

 through composting. 



Because woodchips are a rich 

 source of energy, in die form of 

 carbon (C) for microorganisms, using 

 them as mulch without composting 

 will cause severe competition for 

 available soil N between the micro- 

 organisms and the roots of the plants. 

 Since the affinity for N by micro- 

 organisms is greater than that of 

 plants, newly-planted plants and 

 shallow-rooted species will be most 

 severely affected. The plants general- 

 ly respond by droppuig their older 

 leaves, ceasing to grow and generally 

 being more susceptible to diseases 

 and insects. The lower leaves are the 

 first to be affected because the N 



remaining in the plant is transferred 

 from the older leaves to the growing 

 points. Although newly-planted 

 plants are more susceptible than 

 established plants, established plants 

 will also succumb to the same 

 symptoms. It will just take longer. 

 Dr. Francis R. Gouin is Chairman 

 of the Department of Horticulture at 

 the University of Maryland at College 

 Park. This is his first appearance in 

 The Plantsman. 



MARKETING 

 TIPS 



From Tina Sawtelle 







It takes six times as many 



marketing dollars to attract a 



new customer as it does 



to cultivate a current customer. 



Keep and maintain your 



valuable customer mailing list. 



Use it! 



Direct mail postcards are proven 



marketing tools for specialty 



retailers such as farm stands 



and garden centers. 



Include something 



"For Mailing List 



Customers Only," 



a coupon, 



an entry form, or offer. 



Encourage your customers 



to bring a friend 



and reward them. 



Tuesday is typically 



the day households 



receive the least mail. 



Tina SawteUe is a principal of 



Sauitelle Marketing Associates. 



For information: 



(603) 659-8 J 06. 



April/May 1992 25 



