We assessed adventitious root formation on stem cuttings of mountain fly honeysuckle [Lonicera villosa (Michx.) Schult.] in separate experiments using overhead mist and subirrigation systems. The concentration of applied potassium salt of indole-3-butyric acid (K-IBA) and the proportions of coarse perlite and milled peatmoss in the propagation medium were varied within both systems. Across treatments, 98% of cuttings in the overhead mist system and 85% of cuttings in the subirrigation system produced roots. In the overhead mist system, root volume, root dry weight, and number of root tips were greatest among cuttings treated with 4000 to 12,000 mg·L−1 K-IBA and stuck into 100% perlite. In the subirrigation system, root dry weight was not significantly affected by K-IBA concentration, but the greatest root volume and number of root tips were produced by cuttings treated with 8000 or 12,000 mg·L−1 K-IBA and stuck into 100% perlite. Despite the natural affinity of mountain fly honeysuckle for moist, organic soils, all of the 18 rooted cuttings we planted in a landscape trial survived and grew appreciably with minimal care over 2 years in a mineral field soil. We conclude that cuttings of mountain fly honeysuckle can be propagated readily by overhead mist or subirrigation, that root system quality is improved substantially by increasing K-IBA concentration and using coarse perlite without peatmoss, and that mountain fly honeysuckle can be grown in typical horticultural landscapes.
Darren J. Hayes and Bryan J. Peterson
Bryan J. Peterson, Olivia Sanchez, Stephanie E. Burnett and Darren J. Hayes
Overhead mist (OM) facilitates the propagation of stem cuttings by preventing transpirational water loss. However, drawbacks to OM include the application of large volumes of water, potentially unsanitary conditions, irregular misting coverage, and leaching of foliar nutrients. We explored three alternatives to OM that might avoid these problems by applying moisture below, rather than overhead. These included 1) a submist (SM) aeroponic system configured to provide intermittent mist only to the rooting zone, 2) a subirrigation (SI) system that provided water via capillary action through perlite from a reservoir maintained below the base of each cutting, and 3) a subfog (SF) aeroponic system that was configured to provide constant fog only to the rooting zone. To initiate each system, we wetted perlite or filled reservoirs using either water or quarter-strength Hoagland solution. Stem cuttings of ‘Wizard Mix’ coleus (Plectranthus scutellarioides) were propagated in the systems for 21 days. Cuttings in the SM system produced more than three times as many roots as cuttings in the OM system, with roots more than six times the length. Root dry weights averaged 28 mg for cuttings in the SM system, compared with only 3.5 mg among cuttings receiving OM. The SF and SI systems produced results broadly comparable to the OM. Fertilizer did not consistently improve rooting measures across the systems. Although we observed few fine roots on cuttings rooted using SM, they transplanted well into a soilless substrate and quickly produced new root growth. The SM system used less than 1/5 the water used by the SI system, and less than 1/50 the water used by the SF system. In comparison, a single OM nozzle operating for 10 seconds released about one-third of the total water lost through transpiration from each SM system over the entire experiment. Our results show that SM systems merit further evaluation for propagation of plants by stem cuttings.