Propagation of Acer grandidentatum by Etiolated Cuttings

Bigtooth maple (Acer grandidentatum Nutt.) is a small tree native to the Intermountain West with unrealized potential as a drought tolerant landscaping tree.  Historically, this tree has been difficult to propagate asexually, especially by cuttings.  We examined the effect of etiolation on cutting propagation of six selections of wild bigtooth maple from Cache County, UT grown as hedged stock plants grafted onto seedling rootstocks.  In the spring of 2010, shoots of stock plants were pruned just below the third node from the base of previous season’s shoot growth.  Healthy shoots were randomly assigned to either etiolated or non-etiolated treatments (n = 18, 36, 18, 42, 22, and 39 per respective selection).  Open-ended, black, velour, drawstring bags were placed over selected shoots at bud swell and tied just below the second node allowing shoots from the second node to develop and grow out the end of the bag while maintaining etiolation of the shoot base.  The cuttings were harvested after 3 to 4 weeks, trimmed to two nodes, wounded, and the bases dipped for 5 seconds in 4000 ppm indole-3-butyric acid/ 2000 ppm naphthaleneacetic acid (Dip ‘N Grow).  Cuttings were stuck in a pre-moistened 3 perlite : 1 peat (by volume) rooting substrate in every other cell of a 606 tray (63.5 mm x 63.5 mm x 76.2 mm cells) and placed on heating mats (20-30 °C) under an intermittent mist system (7 s mist/12 min during the day using reverse osmosis water) surrounded by Reemay and in a greenhouse with 60% shade and set at 21/15.5 °C D/N temperatures.  Flats were randomly repositioned on the bench every other day and any dead or diseased leaves removed.  All cuttings were treated with a drench of Mefenoxam 2AQ at 0.6 mL/3.8 L (17 mL solution/cell) after sticking to prevent Phytophthora infection and sprayed weekly with thiophanate methyl (Cleary 3336 WP) at 1 mL/L to prevent Botrytis infection.  Rooting was evaluated after 4 weeks.  Results indicated that overall, etiolated cuttings had 85% rooting and 7.2 roots per cutting (mean of all cuttings), as compared to 17% rooting and 0.5 roots per cutting with non-etiolated cuttings.  We conclude adventitious root formation in bigtooth was significantly increased by etiolation of softwood cuttings.  

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