Prime-Ark 45

Blackberry cultivar Prime-Ark 45 (APF-45) was introduced to broaden the choices of this innovative, thorned primocane-fruiting blackberry type.
This two-season type of blackberry fruits on current-season canes (primocanes) and on second-season canes (floricanes), potentially providing for two cropping seasons, both traditional summer fruits in addition to late summer to fall production. Traditional blackberry cultivars fruit on floricanes, requiring canes to be overwintered toproduce a crop. This fruiting habit has the potential to expand blackberry production much like that which has occurred for primocane-fruiting red raspberries.
In addition to having thornless canes, this Prime-Ark 45 produces large berries with good flavor and is very early ripening on floricanes. Berries of Prime-Ark 45 does not exhibit exceptional postharvest storage potential, and it is not recommended for the shipping market.
The average primocanes length is about 2 m. Primocanes are strong and vigorous, but thornly. Plants like sun placement. Prime-Ark's 45 berries are medium-large size, average weight of berry is about 4-6 g. Color is black. Each plant produces groups of berries, like bunch of grapes. The first yield starts forming at primocanes in the middle of June and continues three to four weeks. During this first harvest season, Prime-Ark 45 intensively produces primocanes, which soon begin bloom. This is the second harvest season, it continues up to first frosts.
After the end of the second harvest season, Prime-Ark 45 requires winter shelter from frost, freezing and cold wind, because the cold-hardy of this blackberry variety is moderate, about minus 13..17 C.

Table 1. Yield and average berry weight of Prime-Jim (APF-12), Prime-Ark 45 (APF-45) and floricane-fruiting varieties Ouachita and Natchez

Cultivar	Yield, kg/ha		Berry weight, g
	2008	2009	2008	2009
Floricane
Prime-Ark 45	13121	4194	6.1	4.7
Prime-Jim	6073	3759	4.6	3.5
Ouachita	8756	4012	5.8	4.7
Natchez	14113	5548	7.9	6.2
Primocane
Prime-Ark 45	986	1565	4.3	5.1
Prime-Jim	84.1	146	3.2	3.3

Table 2. Comparison table of Prime-Ark 45 (APF-45), Prime-Jim (APF-12), Ouachita and Natchez cultivars at the University of Arkansas Fruit Research Station

Main features	Variety
	APF-45	APF-12	Ouachita	Natchez
Floricane flowering date
10% bloom	April 28	April 28	May 3	April 30
50% bloom	May 4	May 5	May 8	May 4
Floricane harvest date
First	June 10	June 8	June 13	June 5
Peak	June 24	June 19	June 30	June 20
Last	July 13	July 17	July 19	July 13
Primocane flowering date
First	June 30	June 13	-	-
Primocane harvest date
First ripe fruit	August 8	July 15	-	-
Fruit (rating scale of 1 to 10 where 10 is the best)
Firmness	8.1	6.6	8.1	7.7
Flavor	7.7	6.4	8.1	7.5
Soluble solids, %	9.6	8.8	10.5	9.2
Plant (rating scale of 1 to 10 where 10 is the best)
Vigor	7.4	7.6	7.0	6.8
Health	7.4	7.7	7.7	7.3

1. Avoid wet area when planted new bushes;
2. Annual spring nitrogen fertilization (56 kg/ha) using ammonium nitrate;
3. Additional fertilization (23 kg/ha) after the floricane crop production is completed in July;
4. Tipping primocanes at 42 inch height two times each season usually in mid-June and late July or early August;
5. Dormant pruning of primocane-fruiting plants must include removing dead floricanes and removing primocane tissue to a point below the fruiting (flowering) area on the primocanes;
6. Dormant pruning of floricane-fruiting plants must include removing dead floricanes and pruning lateral branches to ~ 0.4 m in length;
7. A single application of iron sulfate in late fall (October) and lime sulfur (94 L/ha) at budbreak in early spring;
8. Plant spacing at least 0.6 m;
9. Use sun shelters.