Overhead Mist Research Articles

Propagation of Herbaceous and Woody Perennials in Submist and Overhead Mist Systems

Abstract Submist aeroponic propagation systems apply mist to the bases of cuttings, rather than from overhead. These systems improve rooting in some plant species and reduce water usage compared to overhead mist systems. Submist systems, which were supplemented with infrequent overhead mist, were used to propagate stem cuttings collected from six plant species: bluestar (Amsonia tabernaemontana Walter), purple smoke false indigo (Baptisia australis x B. alba ‘Purple Smoke'), threadleaf coreopsis (Coreopsis verticillata L.), panicle hydrangea (Hydrangea paniculata Siebold), sweetgale (Myrica gale L.), and ninebark (Physocarpus opulifolius (L.) Maxim ‘Diablo'). The submist systems were compared to traditional overhead mist with a solid propagation medium. Rooting was better in overhead mist for cuttings of threadleaf coreopsis and purple smoke false indigo. Rooting was comparable between systems for all other species (bluestar, panicle hydrangea, sweetgale, and ninebark). In the submist systems, water usage was reduced by 67% compared to overhead. This is probably due to reduced evaporative water loss and more targeted application of water directly to cuttings, resulting in less water lost on the ground or benchtops. Species used in this study: Amsonia tabernaemontana Walter, Baptisia australis x B. alba ‘Purple Smoke', Coreopsis verticillata L., Hydrangea paniculata Siebold, Myrica gale L., Physocarpus opulifolius (L.) Maxim ‘Diablo'. Chemicals used in this study: KIBA (potassium salt of indole-3-butyric acid).

Propagation of Five Species in a Commercial-scale Submist System

The novel propagation system submist, which applies water to the bases of cuttings rather than overhead, is a promising alternative. We developed and tested a commercial-scale submist system to make this propagation system more accessible to commercial propagators. Five species, including blue star flower (Amsonia tabernaemontana), faassen nepeta (Nepeta ×faassenii ‘Six Hills Giant’), panicle hydrangea (Hydrangea paniculata ‘Grandiflora’), sweetgale (Myrica gale), and sweetfern (Comptonia peregrina), were propagated from cuttings in commercial-scale submist and overhead mist systems. Blue star flower and faassen nepeta cuttings had greater root length, root rating, and root number with the submist system. Panicle hydrangea cuttings had more roots in submist, but longer roots in overhead mist. There were no differences in rooting between the systems for sweetgale and sweetfern cuttings. The comparable or superior rooting of these five species in a submist system compared with traditional overhead mist systems is evidence that submist is a viable alternative propagation system. Water use in submist systems was 98% less than that for overhead mist systems.

Environment, Photosynthesis, and Adventitious Rooting of Manchurian Lilac Cuttings Propagated in Overhead Mist, Submist, and Combination Systems

We propagated manchurian lilac (Syringa pubescens subsp. patula ‘Miss Kim’) vegetatively from stem cuttings using overhead mist, submist, and combination propagation systems. Cuttings were collected when terminal buds were already set, after the period of tender growth that is optimal for lilac propagation. Net photosynthesis (Pn) was recorded to assess whether differences in rooting could be attributed to differences in photosynthetic activity of cuttings within each system. The propagation environment differed significantly among systems, with vapor pressure deficit (VPD) substantially greater for submist systems than for overhead mist or combination systems, and root zones warmer in submist and combination systems than in overhead mist. Pn of cuttings did not differ among systems and was initially low, but increased about when the first root primordia were visible. Rooting percentages were 90% among cuttings in the combination system, with cuttings in overhead mist and submist rooting at lower, but similar, percentages (68% and 62%, respectively). Cuttings in the combination and submist systems produced significantly more and longer roots than those in the overhead mist system, and retained nearly all of their leaves. Overall, the use of systems that provide intermittent mist to the basal end of each cutting was effective for propagating manchurian lilac. Our results demonstrate that cuttings in submist alone experience a much greater VPD than those in overhead mist, but may nonetheless root at comparable percentages and produce superior measures of root system quality. Combination systems show promise for rooting of species like manchurian lilac, because cuttings rooted at high percentages and with consistent root system quality, despite having been collected after the optimal spring period for lilac propagation.

Vegetative Propagation of Mountain Fly Honeysuckle (Lonicera villosa) by Overhead Mist and Subirrigation

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.

Submist is Effective for Propagation of Korean Lilac and Inkberry by Stem Cuttings

Although overhead mist revolutionized the propagation industry, it does suffer from potential drawbacks that include the application of large volumes of water, potentially unsanitary conditions, irregular misting coverage, and leaching of foliar nutrients. We explored the feasibility of submist as an alternative as it might avoid these problems by applying water exclusively from below the cutting, which is inserted basally into an enclosed rooting chamber. We propagated cuttings of korean lilac (Syringa pubescens ssp. patula) and inkberry (Ilex glabra) using both overhead mist and submist to compare effectiveness of the systems. Cuttings of korean lilac were wounded and dipped basally into 8000 mg·L−1 of the potassium salt of indole-3-butyric acid (K-IBA), and those in the overhead mist systems were inserted into coarse perlite. Cuttings of inkberry were wounded and treated with 5000 mg·L−1 K-IBA, and those in the overhead mist systems were inserted into 50:50 peat:perlite (by vol). Cuttings of korean lilac in the submist systems produced more than twice as many roots as cuttings in the overhead mist systems, with roots more than 2.6 times the length. Similarly, cuttings of inkberry in the submist systems produced more than three times the root counts and root lengths as cuttings in the overhead mist systems. For korean lilac, root dry weights averaged 58 mg for cuttings in the submist system, compared with only 18 mg among cuttings receiving overhead mist. Likewise, root dry weights averaged 70 and 7 mg for cuttings of inkberry propagated by submist and overhead mist, respectively. Rooted cuttings of korean lilac transplanted well into a soilless substrate, where they more than tripled their root biomass to 218 mg (vs. 59 mg for cuttings transplanted from overhead mist). We did not evaluate transplant performance of inkberry. Our results show that submist systems might merit consideration for the propagation of woody plants by leafy stem cuttings.

Comparison of Four Systems for Propagation of Coleus by Stem Cuttings

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.

PROPAGATION AND PRODUCTION OF ZAMIOCULCAS ZAMIIFOLIA

PROPAGATION AND PRODUCTION OF ZAMIOCULCAS ZAMIIFOLIA

Photosynthetic Daily Light Integral during Propagation Influences Rooting and Growth of Cuttings and Subsequent Development of New Guinea Impatiens and Petunia

A majority of commercial propagation of herbaceous ornamental cuttings occurs during the winter when the photosynthetic daily light integral (DLI) is relatively low. We quantified how the mean DLI influenced rooting and subsequent growth and development of two popular vegetatively propagated species, New Guinea impatiens (Impatiens hawkeri Bull.) and petunia (Petunia ×hybrida hort. Vilm.-Andr.). Three cultivars of each species were propagated under a mean DLI ranging from 1.2 to 10.7 mol·m−2·d−1. Cuttings were rooted in a controlled greenhouse environment maintained at 24 to 25 °C with overhead mist, a vapor-pressure deficit of 0.3 kPa, and a 12-h photoperiod. Rooting and growth evaluations of cuttings were made after 8 to 16 d. In a separate experiment, rooted cuttings under DLI treatments were then transplanted into 10-cm containers and grown in a common greenhouse at 21 ± 2 °C under a 16-h photoperiod to identify any residual effects on subsequent growth and development. In both species, rooting, biomass accumulation, and quality of cuttings increased and subsequent time to flower generally decreased as mean propagation DLI increased. For example, root number of petunia ‘Tiny Tunia Violet Ice’ after 16 days of propagation increased from 17 to 40 as the propagation DLI increased from 1.2 to 7.5 mol·m−2·d−1. In addition, cutting shoot height decreased from 6.3 to 4.5 cm, and root and shoot dry biomass of cuttings harvested after 16 days of propagation increased by 737% and 106%, respectively. Subsequent time to flower for ‘Tiny Tunia Violet Ice’ from the beginning of propagation decreased from 50 to 29 days as propagation DLI increased from 1.4 to 10.7 mol·m−2·d−1 regardless of the DLI provided after propagation. In New Guinea impatiens ‘Harmony White’, root and shoot dry weight of cuttings increased by 1038% and 82%, respectively, and subsequent time to flower decreased from 85 to 70 days as the propagation DLI increased from 1.2 to 10.7 mol·m−2·d−1. These experiments quantify the role of the photosynthetic DLI during propagation on the rooting and subsequent growth and development of vegetatively propagated herbaceous ornamental cuttings.

Low-temperature storage influences morphological and physiological characteristics of nonrooted cuttings of New Guinea impatiens ( Impatiens hawkeri)

Herbaceous shoot-tip cuttings of New Guinea impatiens ( Impatiens hawkeri) are commonly harvested in equatorial countries and then packaged, shipped, and subsequently rooted by greenhouse growers in subtropical and temperate climates. We quantified how storage temperature (0–30 °C) and duration (0–5 d) influenced chlorophyll fluorescence, gas exchange, and visual quality of nonrooted cuttings of New Guinea impatiens ‘Harmony White’ and ‘Harmony Magenta’ and their subsequent survival, rooting, growth, and development. Stock plants were grown at 23.2 ± 1.7 °C (mean ± standard deviation) under a 16-h photoperiod and a mean photosynthetic daily light integral (DLI) of 9.2–12.3 mol m −2. Cuttings were harvested and stored for 0, 1, 2, 3, 4, or 5 d at 0.7 ± 2.2, 5.7 ± 1.8, 10.9 ± 1.2, 15.3 ± 0.7, 21.0 ± 0.5, 26.2 ± 0.7, or 30.0 ± 0.6 °C. Rooting occurred in a controlled greenhouse environment with overhead mist, a vapor-pressure deficit of 300 Pa, mean air and media temperatures of 24.2 ± 1.7 and 23.7 ± 1.7 °C, respectively, a mean DLI of 3.9 mol m −2, and natural photoperiods. As storage duration increased from 0 to 5 d at 0 °C, chlorophyll fluorescence and visual quality decreased by 65% and 80% in ‘Harmony White’ and by 76% and 80% in ‘Harmony Magenta’, respectively. In addition, net photosynthesis had decreased from 10.6 to 2.4 μmol m −2 s −1 and respiration increased from 1.4 to 2.0 μmol m −2 s −1 in ‘Harmony White’ cuttings when measured after 11 d of propagation. The fresh-weight loss percentage was <12% in both cultivars after 5 d storage at ≤10 °C. Survival, rooting, and visual ratings after 16 d of propagation were negatively influenced by storage temperatures ≤5 and >25 °C. However, there were no significant trends on the effects of storage temperature and duration on subsequent time to flower, number of lateral branches formed, and plant height in cuttings. These results indicate that New Guinea impatiens cuttings can be stored for up to 5 d at 10–20 °C, with little or no impact on postharvest photosynthetic recovery, survival, visual quality, rooting, and subsequent plant performance.

DAILY LIGHT INTEGRAL INFLUENCES ROOTING AND QUALITY OF PETUNIA CUTTINGS

DAILY LIGHT INTEGRAL INFLUENCES ROOTING AND QUALITY OF PETUNIA CUTTINGS

Low pH Enhances Rooting of Stem Cuttings of Rhododendron in Subirrigation

Abstract Semi-hardwood terminal stem cuttings of Rhododendron L. ‘P.J.M.’, R. ‘Catawbiense Album’ and R. ‘Purple Gem’ were treated with a solution of 0.1% indolebutyric acid and 0.5% napthaleneacetic acid and inserted into perlite for rooting under subirrigation, without overhead mist, at solution pH of 4.5 or 7.5. All cultivars rooted in higher percentages and produced larger root balls at pH 4.5 than at pH 7.5. A second study with softwood stem cuttings of R. ‘P.J.M.’ and both softwood and semi-hardwood stem cuttings of R. ‘Purple Gem’ confirmed these findings and included an additional subirrigation treatment, a sphagnum peat slurry, pH 4.1, which produced nearly identical results to the pH 4.5 treatment.

セル成型苗個体群の連続秤量に基づく自動潅水システムの試作

Water (or moisture) content of soil-mix in a plug tray with limited-volume can easily be changed by evapotranspiration from a plug sheet and watering. Thus, timing and the amount of watering are the most important skills in plug seedling production. An automatic watering system for controlling water content of soil-mix in a plug tray was developed. A tomato plug sheet consisting of plug seedlings, soil mix in a greenhouse was watered by the watering system. The weight of the plug sheet was measured continuously with an electronic balance. When the weight of the plug-sheet decreased to a lower-limit setpoint by evapotranspiration, a solenoid switch of the watering system with overhead mist spray nozzles was turned on, and the plug sheet was watered. When the weight of the plug-sheet increased to a higher-limit setpoint by watering, the solenoid switch of the watering system was turned off. Watering was conducted only during the daytime. In this way, the weight of the plug sheet was controlled accurately in a range between the lower- and higher-limit setpoints during the culture period.

Mist Irrigation Reduces Post-transplant Desiccation of Bare-root Trees

Abstract Desiccation during storage and reestablishment is a major factor contributing to poor regrowth of transplanted bare-root trees. The effect of overhead mist irrigation on reducing post transplant water stress in Norway maple (Acer platanoides L. ‘Emerald Lustre’) and Yoshino cherry (Prunus x yedoensis) was examined. Bare-root Norway maple (desiccation tolerant) and Yoshino cherry (desiccation sensitive) trees were transplanted into pine bark-filled containers and subjected to mist or non-mist treatments. Stem xylem water potential, relative water content, and survivability were determined. Xylem water potential increased (became less negative) for misted maple and cherry trees. Water potential increased for non-misted maple and decreased for non-misted cherry trees. Twenty-seven percent of non-misted cherries were evaluated as nonmarketable due to stem dieback compared to 0% for misted trees. Results of this study indicate that mist irrigation effectively reduces desiccation damage for desiccation sensitive species such as cherries and hawthorns.

Plant Propagation using an Aero-hydroponics System

Abstract Hydroponic and aeroponic methods have been used to study the propagation and growth of plants (1, 2, 4). A combination of these two methods of liquid culture, aero-hydroponics, has been developed (3). Known as the Ein Gedi System (EGS), this aerohydroponics method incorporates the advantages (buffered nutrient capacity of hydroponics and water oxygenation of aeroponics) of both types of liquid culture. The objective of this study was to compare aero-hydroponics (EGS) and solid media for cutting propagation with and without overhead mist.

A Leaf Blight ofEucalyptusSeedlings in South African Nurseries Caused byHainesia lythri

SYNOPSIS Heavy losses occurred in frost-tolerant gum nurseries in the eastern Transvaal in spring 1982, 1983 and 1984. Affected seedlings showed severe leaf spotting, stunting, multiple stems and death. Isolations from symptomatic tissues consistently yielded Hainesia lythri, which was pathogenic on inoculated seedlings. Host range studies showed the following Eucalyptus species to be susceptible; E. fastigata, E. fraxinoides, E. nitens, E. cloeziana, E. camaldulensis, E. diversicolor, E. macarthurii, E. maculata, E. melliodora, E. microcorys, E. orcades, E. smithii and E. tereticornis. E. grandis and E. deanei were resistant. Infection occurred only when leaves were wounded and free moisture was present. In the nurseries studied, leaves were wounded by application of granular fertilisers and overhead mist irrigation systems provided free water for infection.

Pest and disease control on intensive apple trees by overhead mobile spraying

AbstractIn 3 year field experiments on pest and disease control by mobile overhead spraying of intensive Cox's Orange Pippin apple trees, overhead booms applying 1125 litres/ha and overhead mist‐blowing equipment applying 562 litres/ha, each spraying two complete rows from one alley in half the normal time, were compared with conventional automatic mast spraying at 2250 litres/ha and with conventional mist‐blowing at 562 litres/ha. The overhead boom application of demeton‐S‐methyl (0.0036% a.i.) with azinphos‐methyl (0.0165% a.i.) or of fenitrothion (0.031% a.i.) at the green cluster stage gave control of the applegrass aphid, Rhopalosiphum insertum, virtually equal to that obtained by conventional application of the same insecticides. Similarly, the overhead mist applications of conventional quantities of insecticides gave equal control, but not when applying one‐quarter of the normal amount of insecticides. The conventional methods generally gave better control of apple sucker, Psylla mali. In 1971, when the incidence of apple scab, Venturia inaequalis, was only moderate, the overhead boom method gave equal control to conventional spraying with both dodine/captan (0.03% a.i. and 0.094% a.i.) and benomyl (0.025% a.i.) programmes: in 1972 and 1973, when the scab incidence was heavier, the overhead boom spraying was again equal to the conventional method with the benomyl programme but was less effective with the dodine/captan programme. The overhead mist applications gave control only when the scab incidence was light. Repeated applications of dinocap emulsion (0.025% a.i.), included in the fungicide programme in 1971, gave as good control of the active stages of fruit tree red spider mite, Panonychus ulmi, when applied by the overhead methods as by conventional spraying, but application of the benomyl programme gave poor control. Mobile overhead spraying of small intensive apple trees is a promising method but needs further development before becoming fully acceptable.