Journal of the APS Vol 72 Number 3 July 2018

J ournal of the A merican P omological S ociety

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plot was harvested twice per week or as nec- essary from 2012-2015. Total fruit weight and weight of 30 fruit from each plot were recorded for each harvest. Fruit weight and fruit yield data of erect and primocane fruit- ing cultivars were analyzed with ANOVA by Statistix (Tallahassee, FL). Since there was only one high tunnel and one field planting for each blackberry type, they were analyzed separately and could not be compared statis- tically. For semi-erect cultivars, due to lim- ited degrees of freedom, standard deviation was calculated for yield data instead of ANO- VA. Standard deviation was also calculated for cane winter damage data. Results and Discussion  Weather data and plant winter damage . Fig. 1 presents winter and spring daily mini- mum temperature data from 2011 to 2015. Blackberry plant performance was closely related to weather conditions in northern New Mexico. The winters of 2011/12 and 2012/13 both had minimum temperatures of -20°C or lower in Dec 2011 and Jan 2013. The winter of 2013/14 had fewer extremes in mid–winter than the winters of 2011/12 and 2012/13, but there were more late frosts (0

°C or lower) in April and May 2014 (Fig. 1). Regardless of growing habit or cultivar, field plantings had more winter cold injury than the high tunnel plantings (Table 1). Plants suffered more winter cane damage in 2012 and 2013 than in 2014 and 2015 (data not shown for 2014 and 2015). Even though the canes in high tunnels were green in spring of 2012 and 2013, the buds on the floricanes of some plants never broke and laterals only emerged on the lower 30-50 cm of floricanes. Clark et al. (2012) mentioned that winter in- jury of floricane-fruiting blackberry cultivars is a big concern in mid-western and northern U.S. It is also true in the Southwestern U.S. at high elevation areas such as in northern New Mexico. The floricane-fruiting blackberry crop is not reliable in these areas because of winter minimum temperatures.  For the two semi–erect cultivars tested, ‘Chester Thornless’ was more cold hardy than ‘Triple Crown’ in the field in 2012 (Ta- ble 1). In NewYork, ‘Chester Thornless’ was also reported more cold hardy than others (Weber, 2013). For erect cultivars, Ouachita was more cold hardy than ‘Natchez’ and ‘Na- vaho’ in both 2012 and 2013 (Table 1) in the field. In 2014 and 2015, all floricanes over-

Fig. 1.

279

15

2011/12

2012/13

10

2013/14

2014-15

5

0

-5

-10

-15

Minimal temperature (°C)

-20

-25

1-Dec 16-Dec 31-Dec 15-Jan 30-Jan 14-Feb 1-Mar 16-Mar 31-Mar 15-Apr 30-Apr 15-May 30-May

280

Figure 1. Daily air minimum temperatures for Dec. to May from 2011-2015 at Alcalde, NM.