Day-neutral strawberries have the potential to fruit throughout the growing season as long as maximum air temperatures do not exceed 32.2 °C for extended periods. Appropriate temperatures for season-long production of day-neutrals occur in the southern Appalachians at 900 m elevations and above. Replicated studies were conducted at Laurel Springs (900 m elevation) in northwestern N.C. in 2002–04 to determine the most promising combinations of mulch types, planting dates and cultivars. Plasticulture establishment recommendations were followed and white/black plastic mulch compared to black. Dormant plants were established 15 Apr., 1 May, or 15 May at 12 × 12 inch spacing in 2002; plug plants on 30 Oct. 2002 at 12 × 12 inches and overwintered under rowcovers for 2003; and plug plants on 25 Sept. 2003 or 23 Oct. 2003 at 18 × 12 inches and overwintered under rowcovers for 2004. Plants came from commercial sources. Aromas, Diamante, Everest, and Seascape were included in 2002; Diamante, Everest and Seascape in 2003; and Everest and Seascape in 2004. Harvest season lasted 11 weeks in 2002, 12 weeks in 2003, and 10 weeks in 2004. Only main effects were statistically significant. White and black plastic mulch yields were significantly higher than black two years out of three. Fall planting resulted in earlier onset of production and higher yields in most cases. Planting date was important; for fall planting, midto late September was superior to October planting, and for spring planting, middle to late April was superior to mid-May. A plant spacing of 18 inches between plants in rows and 12 inches between rows was important to avoid crowding when planting in fall. Everest and Seascape had the best overall performance.
The genus Kalmia L. is endemic to North America. Kalmia latifolia is the best known species in the genus. It is a rounded evergreen shrub to small tree that ranges from northern Florida to New England. Flower color varies from white to pink, but at lower elevations in the southeastern U.S., pink flowers quickly fade to white. It is a diploid species with 2n = 2x = 24 chromosomes. Kalmia angustifolia var. caroliniana only occurs in the southeastern US. It is a thin upright evergreen shrub to 1.5 m tall. Flower color is either light pink or rosy purple, and the flower pigments appear to be heat stable. It is also diploid. Kalmia latifolia has not crossed readily with any other Kalmia species to date, but a small number of hybrids have been produced. The objective of the present study was to intercross K. angustifolia var. caroliniana with K. latifolia to attempt to develop color stable pink flowered Kalmia hybrids for warm climates. The crosses were made at Cary, N.C., from late April through mid May and included two clones of each species. Only one parental combination was successful and involved a rosy purple form of the former species. With this cross 15 mature seed capsules resulted from 38 pollinations. Numerous seedlings initially germinated, of which about 15% were albinos. Only 38 seedlings survived to transplanting. Thirty seedlings remain relatively vigorous 8 months after potting and are phenotypically intermediate between the parents. Their potential will depend on their ornamental characteristics once they reach maturity.
James R. Ballington and Barbara J. Smith
Thirty-three accessions of Fragaria virginiana collected from Mississippi in 1995 were evaluated for horticultural traits and leaf disease resistance at Reidsville, N.C., and strawberry anthracnose resistance (Colletotrichum acutatum and C. fragariae) at Poplarville, Miss., in 1997. The range of variability in berry shape, fruit flesh color, fruit skin toughness, and degree of sunkenness of seeds among accessions indicated probable introgression with F. xananassa in most all accessions. Seventeen of 29 accessions screened for resistance to C. acutatum were resistant, and an additional 10 were tolerant. Overall, these accessions appear to be good additional sources of resistance to this, the prevalent species of anthracnose in the southeastern United States. In addition, the majority of accessions appear to be tolerant-resistant to leaf scorch, leaf blight, and/or powdery mildew. Nine accessions were resistant to all three leaf diseases, and four were resistant to C. acutatum as well as the three foliar diseases. No accessions were resistant to C. fragariae and only five were tolerant. All five accessions tolerant to C. fragariae were also either resistant or tolerant to C. acutatum but the converse was not true.