IDENTIFICATION OF BLUEBERRY VARIETIES 3 



How Blueberry Varieties Differ 



Variation or difference between individuals is a cardinal principle of nature. 

 The differences between varieties are greater than those between individuals 

 within a variet\ . Vet within a variety- some characteristics var\- more than 

 others; for example, within a variety of the cultivated blueberry leaf size varies 

 considerably, whereas the presence or absence of leaf serrations varies little, if 

 an\\ By stud>ing the different characteristics of the varieties and their natural 

 limits of \'ariation, one learns to distinguish one variety from another. Some 

 differences are obvious and easily learned; others are less obvious and require 

 some stud\'. Some of these differences between varieties of cultivated blueberries 

 are described and illustrated in the following paragraphs. 



Characters Useful in Identification 



The leaf blade is the most important part of the blueberry- plant for the purpose 

 of identification b\- vegetative characters. It has several characters which are 

 ^'er\• useful. However, since the leaves vary considerably, the question arises 

 as to which leaves should be considered as topical of the v'ariety. Clark and 

 Gilbert (5) after making a large number of measurements decided that leaves 

 4-5-6 on lateral branches 8-12 inches long exhibit the least variability as regards 

 the measurements the>- made and, therefore, suggest their use as criterion leaves. 

 The use of such criterion leaves is undoubtedly advisable in a system of identi- 

 fication based on definite measurements such as these authors proposed. How- 

 ever, in a system such as Shaw and his associates have developed, such definite 

 measurements, except for experimental purposes, are not necessary. With 

 sufficient study certain varietal characteristics will stand out and can be found 

 without limiting the observer to certain leaves on branches of a certain size. 

 This o\'er-all sort of observation is particularK* important in examining a nursery 

 where branches of a particular size might be difficult or impossible to find. Hence, 

 the authors believe that the selection of criterion leaves must be left for the 

 observer to determine according to the condition of the bushes under observation. 



Leaf shape varies considerably among varieties and is, therefore, a very useful 

 characteristic. Typical leaves of Wareham are narrow elliptic, those of Pioneer 

 elliptic. Leaves of June are ovate, while those of Jerse}- are oval, and those of 

 Grover are obovate (Figure 1). 



Closely related to leaf shape are length/width ratio and apex and base angle. 

 As pointed out by Clark (4) and Clark and Gilbert (5), the width/length ratio 

 is very useful for identification. However, the actual measurement and calcula- 

 tion of this ratio in the field is too time consuming. Therefore, a simplification 

 illustrated in Figure 2, which gives the reverse or length/width ratio, has been 

 adopted. The tip of the leaf is bent back to the base and the leaf broken in two 

 at the mid-point. The broken edge of the top half is then placed along the midrib 

 of the bottom half. If the length of the half midrib is greater than the width 

 of the leaf, the ratio is greater than 2. If they are equal, the ratio is 2. If the 

 length of the half midrib is less than the width, the ratio is less than 2. Thus, 

 varieties can be roughly and rapidly separated into three groups. In Figure 2 

 Scammell represents the group with ratio greater than 2, Pioneer 2, and Jersey 

 less than 2. 



