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  • Author or Editor: John R. Havis x
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Abstract

Stomatal resistance (rs) was measured in Cornus florida L., Magnolia × soulangeana Soul., Rhododendron cv. Nova Zembla and Viburnum carlesii Hemsl. in containers with a range of different matric potentials (ψm). Significant increase in rs occurred at potentials between −250 and −390 millibar (mb) in clear, warm weather. Minimum ψm of −200 mg is suggested to avoid water stress.

Open Access
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Abstract

Root hardiness is reported for 38 container-grown woody ornamentals taken from commercial nursery storage in mid-winter. Lethal root temperature ranged from −5° to −23.3°C.

Open Access

Abstract

Hardiness of intact roots of Potentilla fruiticosa L. cv. Katharine Dykes and Picea glauca Voss were determined during the autumn. Both extended photoperiod and warm temperature interfered with root acclimation to cold. Seasonally short days and near freezing temperature were necessary for maximum rates of cold acclimation of roots.

Open Access

Abstract

Cold hardiness of branch, lower stem and root parts of Rhododendron cvs. Mother’s Day (evergreen) and Homebush (deciduous) were determined after artificial acclimation. Lower stems of the evergreen azalea acclimated more slowly than the upper branches. In the deciduous azalea the lower stems acclimated more rapidly than the upper branches initially, but both parts were equal in hardiness after 53 days of acclimation. The lower stem of the deciduous acclimated more rapidly than that of the evergreen azalea.

Open Access

Abstract

Warm root environments interfered with cold acclimation in roots and lower stems sections of Rhodendron cv. Springtime.

Open Access

Abstract

Growth of rhododendron rooted cuttings was induced by keeping them at a minimum night temperature of 18.3°C until buds began to swell (10 to 14 days). This treatment produced a subsequent flush of growth that occurred at minimum 4.4° and resulted in spring growth of rooted cuttings of Rhododendron ‘Nova Zembla’ and fall growth of R. ‘PJM hybrids’ with potentially large savings in heat.

Open Access