This article provides general information on blueberry roots and highlights recent work on the topic as part of a multi-year research project investigating organic production options for highbush blueberry in the Pacific Northwest. For more information on this project, see Organic Blueberry Production Research Project.
Objective: Evaluate the effects of organic management systems on soil water and nutrient availability and the distribution of blueberry roots. The management systems being compared include flat vs. raised planting beds, sawdust mulch vs. weed mat (used for weed control), and two different rates of organic fish fertilizer: 25 and 50 lb/acre of N (29 and 57 kg/ha of N).The timing of new root development is also being examined. The knowledge of when new root growth occurs will be useful for determining when and where irrigation water and fertilizers should be applied.
Roots are monitored in this study by way of a series of digital photographs, which are taken in the soil every two weeks (Fig. 2). The photographs are taken inside clear plastic tubes, referred to as minirhizotrons, which are installed near the plants at a depth of approximately 2 feet (60 cm). From these images, information is gathered about when new roots appear and when old roots die, the total number of new roots produced on the windows, root diameter and length, and any changes in root color.
Figure 2. [left] Minirhizotron camera used to photograph roots of a blueberry plant in the field at the OSU North Willamette Research & Extension Center. [right] An image of blueberry roots taken with the minirhizotron camera. Roots are highlighted (red line = first-order root; green line = second-order root) using computer software designed to measure root characteristics. Photo credit: Luis Valenzuela, Oregon State University.
After the first three years of the experiment, the plants produced more roots (1) in raised beds than in flat beds, (2) with sawdust mulch than with weed mat, and (3) with the lower rate of fish fertilizer than with higher rate of fertilizer (Fig. 3). Plants on raised beds and grown with less fertilizer also produced deeper roots (Fig. 4). In 2009, during the third year after planting, a flush of new root growth was observed immediately after fruit harvest (data not shown).
Figure 3. Effects of bed type (A), weed control method (B), and amount of organic fish fertilizer (C) on new root production in "Duke" blueberry. Different letters above the bars indicate a significant difference at P = 0.05.
Although more irrigation water was applied to raised beds than to flat beds, raised beds with sawdust mulch generally had lower soil water content than raised beds with weed mat, or than flat beds with sawdust or weed mat (Fig. 6). Differences in irrigation and soil water content often affect soil chemistry and root dynamics and therefore may account for some of the differences in root production observed in the present study. For example, less soil water content in the raised beds may have resulted in more root production in the beds (Fig. 3A). Lower soil water content may have also increased root production under sawdust (Fig. 3B), although daytime soil temperature was also lower under sawdust, particularly in late July and early August after harvest (data not shown).
I am often called to look at newblueberry plantings to determine what is wrong because of poor growth. Manytimes the field was planted before the soil was tested and the soil pH was toohigh for blueberries. Blueberries prefer a soil pH of 4.5 to 5.5.
The peat mixtures used to growblueberry plants hold water very well, but the sandy soils in many blueberryplantings do not. As the soil water drains away, there is little reason for theplant roots to grow into the relatively dry sand. This results in a small,restricted root system supporting a relatively large plant. This problem is notapparent early in the season when there are few leaves and the soils are moist.Later as the plant develops leaves, it starts to use more and more water untilthe day comes when the plant sucks all the water out of the little pocket ofpeat soil where its roots are.
I see this problem usually insandy soils, but I also see it in heavier soils. I often see it in young plantswhere they just are not growing. They get off to a good start in the spring andthen just stop and sit there for the rest of the year because the small rootsystem just cannot supply enough water to the leaves to allow the shoots togrow for very long in the spring before they run out of water and stop. Theseplants just sit there year after year. They grow a little bit every spring andthen shut down and hang on for the rest of the growing season. Often, peoplethink the plant needs more fertilizer and sometimes fertilize them to death bygiving them more and more fertilizer to get them to grow. The solution is to digup these stunted, root-bound plants in the spring or fall and replant them. Besure to break up the root ball and replant them.
When you plant blueberries, yourobjective is to grow a big productive bush in eight to 12 years, and that bushrequires a big root system. Make every effort to get the roots off to a goodstart so they can support vigorous growth for years to come. If the root systemis restricted, that plant will always be small.
We often find two peaks in root production in Oregon. The first peak occurs in late spring or early summer and is triggered by high water and nutrient demands for fruit production. The second peak occurs in mid- to late summer, after harvest, as the plants begin to accumulate carbohydrates and nutrients in preparation for dormancy.
In general, blueberry roots do not extend very far from the plant. In most soils, 50% to 60% of the roots are located in the top foot of soil and are within 8 to 12 inches from the crown. However, this rooting pattern can depend on management factors. For example, plants irrigated by drip have roots concentrated near the emitters, while those irrigated by sprinklers tend to produce a uniform layer of roots. Plants also produce more roots when grown on raised beds than on flat ground and produce deeper roots with weed mats than with sawdust mulch.
In sandy soils, roots will grow deeper than in clay or silt loam soils. In Florida, where a pine bark system is often used, blueberry roots will only grow in the upper pine bark layer, which has the preferred lower soil pH and a higher organic matter than the sandy soil below.
When temperatures become too cool for plant development, flower bud differentiation will stop. It typically continues in later winter/spring prior to bloom. Plants then start acclimation, or entering dormancy. Acclimation is the gradual physiological process by which a blueberry plant adjusts to colder winter temperatures.
Water initially moves into the root by osmosis, because the dissolved chemical components of the root cells are higher than that of the surrounding environment. This creates a root pressure that extends into the xylem cells, or water pipes of the plant. Water moves out of the plant as a vapor through the somata, or pores, on leaves. This is called transpiration.
Ripening blueberries in the research plots at the OSU North Willamette Research and Extension Center in Aurora, Oregon. Pruning, cultivar selection and weather all affect the quantity of fruit blueberry bushes produce.
Most of us think more about the part of the blueberry bush above the ground than below, but such is the lot of the gardener. Root depth is necessary information when you are preparing soil to welcome new bushes. The good news is that you won't have to dig to bedrock to allow these easy-care bushes to produce their sapphire treasures.
Three types of blueberries are cultivated in the United States and each has its market nitch. Rabbiteye (Vaccinium ashei) are vigorous bushes for those in the Southeast, lowbush (Vaccinium angustifolium) feed blueberry lovers in the Northeast, while highbush cultivars (Vaccinium corymbosum) make do for everyone else. The blueberry types thrive respectively in U.S. Department of Agriculture plant hardiness zones 7 through 9, 3 through 7, and 6 though 10.
Blueberries are not picky about soil as long as it is acidic with a pH between 5 and 5.5. Still, it helps the plant to establish if you work in several inches of organic compost as you prepare the soil. Blueberry roots are shallow, generally penetrating no deeper than 10 inches, so a garden bed tilled to a foot deep works in well-draining soil. Dig twice as deep in soil with poor drainage.
The deep bluish-purple liquid gives a hiss upon opening and a sizzle to the pour that settles to silence. As bubbles slowly dissipate and line the glass, the scent is of strong blueberry. Carbonation is foamy in the mouth, revealing a full mouthfeel and moderate consistency. The taste is a deep, rich, juicy blueberry flavor with sweetness from both juice and cane. The spice in the background recalls cloves, making for a flavorful, multi-layered beverage that's like having a blueberry pie in a bottle. This is one that's perfect for those seeking a natural blueberry taste to their soda.
There are two types of blueberries grown in New England. Highbush blueberry (Vaccinium corymbosum) is discussed here. For information on lowbush blueberry (V. angustifolium, V. myrtilloides), contact Lily Calderwood at the University of Maine Cooperative Extension in Orono, Maine.
New England is considered the northern edge of the climatic zone in which highbush blueberries can be grown. As a result, a number of disease problems associated with cold stress, particularly canker diseases, are more common here than in other blueberry growing areas. High soil acidity (low pH) and relatively high organic matter are essential for optimum production.
Blueberry has very specific soil requirements, dictated by its unique root structure. The blueberry root system is composed primarily of fine, fibrous roots near the soil surface. These fibrous roots lack root hairs, so the root system has a relatively low absorptive capacity. Blueberry roots are unable to penetrate compacted soils and have limited tolerance to excessively wet or dry soils. The shallow root system is sensitive to both high and low temperature extremes. 041b061a72