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- Author or Editor: G. J. Keever x
Dwarf Japanese euonymus (Euonymus japonica Thunb. ‘Microphylla’) and ‘Pink Supreme’ azalea (Rhododendron Xsp.) grown in containers of three diameters (10.2, 15.2, and 20.3 cm), were given three rates of Osmocote 17N-3P-10K (3.6, 7.1, and 10.7 kg·m-3). Response to container volume and fertility was species-dependent. Top growth of euonymus increased in response to both increased medium volume and fertility and was closely related to foliar levels of N, P, and K. Top growth of azalea increased in response to increasing fertility rates in the smallest pots, and to increasing medium volume at the lowest fertilizer rates. With an increase in both fertilizer rate and medium volume, growth of azalea was reduced. Top growth was inversely related to foliar K, but was unrelated to foliar N and P.
Overhead irrigation during the day reduced maximum temperatures and their duration within the plant canopy and the container growth medium, and resulted in increased top and root growth of ‘Hershey’s Red’ azalea (Rhododendron × ‘Hershey’s Red’). Intermittent irrigation for 2.5 min/hr during the day reduced canopy temperature but did not affect growth medium temperature or plant growth.
Three pot/mulch combinations and 2 pot spacings were evaluated as to their effects on growing-media temperatures and growth of ‘Hershey’s Red’ azalea (Rhododendron Xsp.). The highest, maximum temperature and least root and shoot growth occurred in black pots on white clam shell mulch compared to white pots on black polyethylene and to white plywood-shielded pots. Close spacings of pots increased root growth with black pots on white mulch but not with white pots on black mulch. Plants in black pots on white mulch developed the greatest winter foliage discoloration and leaf abscission.
Dwarf Japanese euonymus (Euonymus japonica Thunb. ‘Microphylla’) and Japanese holly (Ilex crenata Thunb. ‘Compacta’), grown in fresh or aged (1 year) pine bark amended with a slow-release complete fertilizer, were supplied with NH4NO3 weekly at 0, 100, 200, or 300 ppm N. Plant growth, foliar color, leaf tissue N, and leachate soluble salts increased with increasing levels of supplemental N while tissue K, Ca, and Mg decreased. Plant growth, foliar color, and leaf tissue N, P, Ca, and Mg in fresh pine bark equaled or exceeded that in aged pine bark at all levels of supplemental N. Leachate soluble salts, pH, and leaf tissue K was higher in aged pine bark.
Greenhouse-grown plants of Zinnia elegans Jacq. were exposed to simulated sulfuric acid rain 30 minutes per day twice a week for 6 weeks at pH 2.8, 4.0, and 5.6. Injury occurred primarily to older, mature leaves and cotyledons at pH 2.8 and 4.0 and to ray flowers at pH 2.8. Plants supplied with higher levels of Hoagland’s nutrient solution grew more rapidly, contained greater quantitities of foliar K, P, and Ca, and exhibited more foliar injury after exposure to acidic simulated rain (SR). Dry weight of plants given full-strength nutrient solution (highest level) was depressed at pH 2.8 and increased at pH 4.0 relative to pH 5.6. Loss of 86Rb by leaching from foliage was significantly increased at pH 2.8, but no differences in total foliar content of K, P, and Ca were detected.
Plant response to time of transplanting from 0.53-qt (OS-liter) to l-gal (3.8-liter) containers was influenced by cultivar and severity of winter. Transplanting of `Formosa' from Sept. through Dec. 1983 resulted in injury and death of many plants due to a low temperature of 8F (-13.3C) in Dec. 1983. Injury or death of `Hino Crimson' was higher when plants were transplanted in December. Survival and growth indices of both cultivars were higher when transplanted in January through March. During 1986-87, when minimum temperature was 26F (-3.3C), transplanting between September and April had minimal effect on growth of `Formosa', but plant quality was better when plants were transplanted between December and April. Transplanting date had little effect on size of `Hino Crimson', except smaller plants were produced when transplanted in April; quality was highest of plants transplanted from November through March.
Rhododendron cuttings absorbed Ν and P from intermittent nutrient mist during propagation; there was no net uptake of K, Mg, or Ca. However, the foliage was injured and rooting was inhibited at all concentrations of nutrient mist. Cultivars differed in sensitivity to nutrient mist. ‘Gloria’ cuttings did not root under distilled water mist and developed symptoms resembling Κ deficiency. Azaleas have low nutritional requirements and nutrient mist during propagation was of no benefit.
Dwarf Burford holly (Ilex cornuta Lindl. & Paxt. ‘Burfordii Nana’), dwarf Japanese euonymus (Euonymus japonica Thunb. ‘Microphylla’), and ‘Hershey’s Red’ azalea (Rhododendron x sp.) were grown in containers in all combinations of 3 diameters (10.2, 15.2, and 20.3 cm) and 3 depths (7.6, 15.2, and 30.5 cm). Top growth of Burford holly, a species with coarse, lateral, and deep roots, increased as pot depth and width increased; root growth was increased in deep pots. Euonymus, a species with a densely branched, medium fine root system, increased in top growth as pot depth and width increased, although the response to pot depth was less than to width. Top growth of azalea, a fibrous and shallow-rooted species, increased as pot width increased but was not affected by pot depth. Root density of euonymus and azalea decreased as pot depth and width increased, whereas relative root depth of azalea was reduced in deep pots.
Improved water use efficiency exists for plants grown in modified containers to minimize leaching and reduce irrigation frequency which subsequently reduces NO3-N leachate. Salvia splendens `Bonfire' and Impatiens wallerana `Pink' (super elfin hybrid) were potted in ProMix BX medium (Premier Brands, Inc., Stamford, CT) into nine container styles with modified drainage holes to determine leachate volume and quantify NO3-N leached. Three styles had four drainage holes on the container side with hole diameters of 0.5, 1.0, and 1.9 cm, respectively; three styles had four drainage holes on the container side and one drainage hole in the bottom center with hole diameters of 0.5, 1.0, and 1.9 cm, respectively; and three styles had one drainage hole in the bottom center with hole diameters of 0.5, 1.6, and 1.9 cm, respectively. Plants were hand watered when an individual container's medium reached 80% of container capacity. Leachate volume, irrigation frequency, and leachate NO3-N was reduced as drainage size hole decreased in size and number. Plant quality was similar among container modifications.
Pampas grass seedlings in 72-cell pack containers were transplanted into containers with a root observation window (17.8 × 10.2 cm) and treated with selected preemergence applied herbicides. Root numbers were counted in the upper and lower 8.9 cm of the viewing window until 16 days after treatment (DAT) when the windows became full of roots. Root growth in both the upper and lower window was suppressed with application of Factor 65 WG and Pendulum 60 WDG at the X and 2X rates at 16 DAT. Ronstar 2G and Pendulum 2G at the recommended rates and nontreated control plants had similar root numbers at 16 DAT. At 16 DAT, the greatest number of club roots formed on plants treated with the dinitroaniline herbicides; Pendulum 2G, Pendulum 60 WDG, and Factor 65 WG. Shoot growth was not affected by treatment.