2019 ASHS Annual Conference

For use in hydroponic production systems, blueberries would ideally be propagated in compatible substrates. In summer 2018, softwood cuttings of Vaccinium corymbosum x angustifolium 'Northland' were rooted. Apical (AP) and basal stem (ST) sections were stuck in rockwool cubes (RC), shredded rockwool (SR), or 3 perlite:1 sphagnum peat moss (v/v; PP). Cuttings were treated with 1,000 ppm IBA (1A), 1,000 ppm K-IBA (1K), 2,000 ppm K-IBA (2K), or distilled water (Control) and were rooted under intermittent mist. Each treatment combination was replicated 6 times with 6 cutting subsamples per experimental unit (e.u.). After 53 days, rooting percentages were calculated and rooting quality was assessed using a 6-point visual scale (0 = dead or no callus, 1 = callus, 2 = few roots, 5 = many roots). AP cuttings had better root ratings than ST (AP 2.7±1.4 and ST 1.9±1.2) as well as better rooting percentages at 80% and 54%, respectively. Root ratings for auxin treatments on AP ranged from 2.6±1.3 to 2.8±1.5 and ST from 1.8±1.3 to 2.1±1.3. Rooting ratings were not different between LR (1.5±0.7) and RC (1.7±0.7), but these were notably lower than PP (3.7±1.2). Differences in substrate rooting percentages were substantial with SR at 46%, RC at 61%, and PP at 95%. Blueberries rooted in hydroponic substrates had no increase in rooting when auxin was applied but had substantially better rooting when apical cuttings were chosen over basal cuttings. The most substantial treatment effect was the type of substrate in which the cuttings were rooted with best rooting occurring in peat:perlite. Despite this, both rockwool substrates could still be used to root blueberry cuttings when the plants will be transplanted into rockwool-based hydroponic production systems.