Blueberry Cultivars

Blueberry Cultivars

[music] Hello everyone, this is Bill Cline. I’m an Extension Specialist in the Department of Entomology and Plant Pathology at North Carolina State University. I’m also the Extension Horticulturist for blueberries. This session will cover blueberry cultivars for the Southeastern US. Before we talk about cultivars. I’d like to give a little background on blueberries. The species of blueberry is vaccinium. They’re in the Heaths family or Ericaceae. Blueberries are native to North America. They’re, they’re related to azaleas, rhododendrons, cranberries. They’re acid-loving plants that require a low soil pH. When you look at a blueberry bush, it’s a multi trunk plant. It’s not a single trunk like a tree. I’d like to see all different ages of wood coming out of the ground. They’re deciduous so they drop their leaves in wintertime, and it’s a woody plant that is a perennial plant that lasts many years. They require winter chilling. They’re a temperate plant that has to have a certain amount of cold weather in the winter in order to leaf and flower normally in the spring. Blueberries are pollinated by insects. Most cultivars will not produce much, if any fruit unless an insect visits the flower. They are typically hand-harvested. We’re seeing a trend toward more machine harvest. Most of the cultivated blueberries are sold fresh, but there’s also quite a lot that is processed, mostly frozen. If we take a look at the blueberry bush and concentrate on the twigs, where the fruit is born. . If you look at the bushes in wintertime, the flower buds that will bloom and produce fruit are quite obvious in the wintertime. They’re the nice fat buds out on the end of the twigs and those will bloom and produce flowers that are pollinated by insects and that is where the berries will be produced that summer. If you follow through to the fall of the year the vegetative shoots that were produced during the summer, during harvest and after harvest, form flower buds in the leaf axles. So if you look at this image with the with the fall color, in the lower right-hand corner you can see flower buds forming in the axles of those leaves. And of course, when the leaves fall off, what will remain will be the terminal flower buds for the coming season’s crop. Just a little bit about culture and management for blueberries. Pollination is essential, you have to have an insect visit each flower or you won’t have a berry form. So, that’s a really critical step in producing the crop. For cross-pollination, it’s best to plant more than one cultivar. Most blueberries are partially self infertile. So having a mix of cultivars will produce more fruit, larger fruit, more seeds in the berries and so you’ll just get a better fruit set with cross-pollination. Other practices, pruning is an annual task, usually in the dormant season, you remove the old and weak canes and shape the bush, thin the crop, most blueberries will overbear if not pruned. In most situations irrigation is essential, especially during the establishment for blueberries. So irrigation, both for a drought relief, we see a lot of drip irrigation systems and micro sprinklers and also for freeze protection There are a fair amount of systems in North Carolina with overhead irrigation for freeze protection As far as fertility and organic matter, the best advice I can give you on fertilizer use is to base it on your soil testing. A lot of sites in North Carolina typically will only need nitrogen, phosphorus, and potassium may be sufficient. One key thing you need to maintain a low pH for the life of the planting, so around 4.5 is ideal. I see sites that range anywhere from 3.9 to 5.3, where bushes are doing okay, so that’s sort of the range we have to work with where your target pH is low. Most sites outside of native blueberry soils require amendment and this is usually pine bark amendment in the soil or aged sawdust again mixed in with the soil, prior to planting. And just an image here of one of the blueberry flowers and one of the pollinating insects. This is a southeastern blueberry bee, it’s a small bumblebee like insect. And again, blueberries have to be visited by an insect in order to form a berry. So this is a critical step. If pollination is not done what you will see is berries that do not size. So what we’re looking at here is a cluster of fruit where some berries were pollinated, and others were not. The small berries that are sort of red-faced will not size. They were not pollinated, so they will fall off two to three weeks after bloom. This is a common phone call from growers after bloom where the berries are falling off and the ones that are dropping are simply the ones that were not pollinated. Blueberry pruning is something that’s done every winter. There’s, there’s also some options for summer pruning in the southeastern US. We’ll talk at length about blueberry pruning in another session here. Just a couple of images to share with you to show, sort of a before and after pruning scheme. You narrow the base of the bush and thin the canes, open up the center of the plant, and reduce the crop load. Very critical step has to be done every winter to keep the bushes in top shape. Overhead irrigation is is quite common for freeze protection in the spring. This is a fairly high volume system with sprinklers, about 12 to the acre. that are capable of keeping the blooms and emerging flowers wet during a freeze event in the spring. If you keep them wet throughout a freeze event form ice and continually form ice until it melts the next day, then you can protect the crop. So that’s the idea behind overhead for freeze protection. Another really common system is drip irrigation system and this is frequently used in areas where water needs to be conserved. Maybe you’re getting from a well and don’t have a lot of water volume so drip systems have been used quite successfully as well. Many of the commercial blueberry growers that I work with are in South Eastern North Carolina, Blatant and surrounding counties and they have blueberry soils that are native blueberry soils. They have a characteristic that allow them to produce blueberries without having to add organic matter or without having to add irrigation. So these fields have high organic matter content, they’re sand-based and have sort of the salt and pepper appearance and no brown color in the soil. So in these fields, the rows are bedded up to keep the roots out of the water, because the water table is within 12 to 24 inches of the surface year-round. So really unique native blueberry sites that produce blueberries quite well. On up-land sites where the cubic matter in the soil maybe low and the water table is quite far away, the site has to be modified. And this is a really common tactic in a lot of parts of the southeast, e especially some of the smaller plantings that that have to amend the site. You see this a lot with with pick your own operations and one, two to three-acre plantings just throughout the southeast. So on these upland sites typically, add the pine bark or peat moss, but I see more pine bark than anything else added to the soil and mixed in as an organic substrate for the blueberries. It’s got a pH of around 4.5, helps with the drainage and on at least on a flat site that you see here in this picture really really try to keep them as much of a raised bed as possible. To me evaluating sites you know that it involves a set of post hole diggers. I think it’s really valuable when you evaluate a site for a grower, trying to determine whether it’s a good blueberry site to go out and do some digging. And you can see what the soil profile is, how well drained the site is. and also find out if there are any restrictive layers or anything that would cause a problem for the blueberries down the road. So site evaluation I think is a critical step. On most upland sites where there are not native blueberry soils, this is what the end result looks like you very often have to you amend beds with pine bark. Grow the bushes on raised beds and then mulch the surface and often with sod in the middle is grass middles, and this system works quite well and and mimics that native characteristic of a well-drained high organic site. In discussing blueberry cultivars, we, of course, have to back up and discuss species. Within each species, there are cultivars that are suited for different areas and of the species that are cultivated, the ones we can grow in the southeastern US, depending on your location, include rabbiteye, highbush, Southern highbush, and some of the newer pentaploid cultivars. Rabbiteyes are vaccinium virgatum they’re native to the Deep South. If you think about Alabama, North Florida, that region. Highbush are quite different, they’re vaccinium corymbosum, it’s also called northern highbush. They were originally domesticated in New Jersey, but also native down into the south we see them in the wild in North Carolina. The third type, Southern high bush, is a complex hybrid. So it’s vaccinium corymbosum crossed with a lot of other species. And so this interspecific hybrid has a lower chill requirement, greater soil adaptability, a lot of good characteristics from the different species that are involved. And just a brief mention of the pentaploids which there are not a lot of them out there, one that comes to mind is Robison, it’s a pentaploid released by NC State University, these are hybrids between rabbiteye and high bush and have characteristics such as ripening season that are sort of in between the two. Blueberry cultivar selection is really driven by your location, the things you have to take into consideration in addition to the soil type and percent human matter that we’ve talked about are things like chill hours and this is the hours below 45 degrees that are required by that species or cultivar in order to leaf and flower normally. So chill hours occurring in North Carolina from October to February and we keep pretty close tabs on that because it helps us to understand why some cultivars do well in our area and some don’t. Another driver of cultivar selection is the USDA hardiness zone and with some cultivars being well adapted to warmer climates and some to colder. If you look at the chill requirements of the various blueberry species , you can see that they have a chill hour range that that sort of corresponds to the USDA hardiness zone. But there’s also a lot of variation within species. So for instance, highbush cultivars may require as little as 800 hours of chilling in the winter to well over 1200 Rabbiteyes tend to be in the 400 to 800 range. The southern high bush are the most widely variable from almost no chill to some cultivars that require as much as 900 hours of chilling and those correspond to the USDA hardiness zone with highbush being the most hardy, Rabbiteye sort of intermediate and southern highbush intermediate down to even out to zone ten. If we correlate that to the plant hardiness zone map and it’s color coded. You can see that the highbush for zone three down to seven highbush blueberries would be, there would be cultivars available all the way from from Canada down into western North Carolina. northern Alabama. So the, the range of highbush is is quite broad and they’re quite cold hardy. If you look at the rabbiteyes, they would be more in the seven and eight range. So this would be if you look at North Carolina, most of the piedmont and coastal plain, most of South Carolina, most of Georgia and so forth. So the seven to eight range on the chill map is the light green to to tan color. And then finally, the Southern highbush, which would be plant hardiness zone seven down to down to ten would go from most of North Carolina down through the southeast and old down into the Florida peninsula. So if we look at North Carolina as an example, when I’m making cultivar recommendations for our state the Highbush cultivars are preferred for the North Carolina mountains and the the elevation I use is about 2500 feet because that seems to correlate with the cold temperatures that are just just too low in the mid winter temperatures for a rabbiteye blueberry. Once you get below 2500 feet for rabbiteyes will do quite well in the lower mountains, footheels, Piedmont and the dryer areas of the coastal plain and the strength of the rabbiteye is their soil adaptability and drought tolerance. So just a really tough bush. And then finally, the Southern highbush and some selected low chill highbush are mostly what’s grown in our main coastal production areas. And the key to with the cultivar selection there is that we’re trying to get early ripening. So really striving to to have an early crop in that part of the state. Once you decide what species of blueberry to grow, I encourage you to research your, your choices, talk to folks about the varieties that you’re looking at. Very often folks will say, “I wouldn’t grow that one because of various reasons.” Some varieties tend towards stimunus, root cracking during wet weather, some of the older cultivars are just are just quite soft or they may have a wet stem scar. So we’ll talk later in this session about the specific cultivars that I would recommend but also encourage you to to do your own homework on this and you may encounter cultivars that are locally popular that are not the ones that I recommend. So there’s a lot of blueberries out there and a lot of good information on those cultivars. So, so I encourage you to to look into and make make good choices. One characteristic that that will disqualify a cultivar from commercial production and can be as simple as as fruit color. Wh have a comparison here, Onslow, the rabbiteye blueberry on the left in this image versus Columbus on the right. There’s a tremendous difference in the waxy bloom. The wax coating on the berries that is natural, that is an indicator of quality. And so the light blue color is desirable. The dark blue is is not and and that alone can disqualify a cultivator or even though all other characteristics are good. One thing that’s been extremely valuable to us in North Carolina has been the local testing and evaluation of cultivars. We’re sort of midway on the East Coast So we can use some cultivars from the north from New Jersey, we can use some of the Florida cultivars. Transplanted north and grown quite well for us. The only way to really find out is to try them. This is a picture of Mike Mainland. He’s an emeritus professor of Horticultural Science at NC State and and a famous blueberry fellow worldwide Mike is retired. But still, still comes in and still works with the blueberries and harvest every year. And just invaluable amount of research and cultural evaluation is come out of his program. If you look at the field that Mike is standing in and you can see bushes that are still dormant and some that are leafed out. So these are characteristics that are occurring because of their chill requirements. So the low chill varieties are leafing and blooming and producing fruit already. The high chill cultivars that may not be suitable for North Carolina are still dormant and they still haven’t, haven’t broken dormancy and haven’t started to come out. If we look at blueberry harvest timing by cultivar in southeastern North Carolina, You can see how our program is weighted. our industry is heavily invested in southern highbush the green color on the chart shows our major cultivars and the time that they ripen. Just a couple of highbush cultivars are in use in the southeastern part of North Carolina, so Duke and the old heirloom variety Croatan are still around. Also, I’d like you to notice the cultivars in red this is the transition to rabbiteye blueberries and notice the, the time of year that they ripen The rabbiteye ripen quite a bit later than the highbush or Southern highbush and rabbiteye ripening being from mid June through August so our season, as you can see, is really heavily weighted towards the, the higher value early, early fruit. So we have lots of colors in it early season. I promised we would get down to specific so cultivars and we’ve reached that point. So I’ll take a look at highbush cultivars first. So these would be for zones three to seven, well drained, ammended soils of irrigation and again highbush are the most cold tolerant. So at higher elevations in North Carolina, these are the only cultivars that can be grown. So our old standards, if you go to the old plantings up in the mountains of North Carolina, you’ll see cultivars like Earliblue, Bluecrop, and Jersey. Some of the newer ones that I like are Duke, which is performing quite well for us, Aurora, Liberty, and Draper. Rabbiteye cultivars in zone seven to eight are really the mainstay of our small pick-your-own operations in the South. So these are what you’re most likely to see in backdoor plantings or pick-your-own plantings in the southeast. They’re mostly irrigated, or at least initially irrigated, mostly amended and upland sites. The old standard cultivars are premier and climax are a couple of the earliest. Brightwells a little bit newer TIFblue is a really common rabbiteye that’s you see in plantings, , and tifblue tends to sprout a lot so it gets transplanted people dig the shoots and move it around. So if someone got a blueberry plant from their neighbor, chances are it’s to the old Georgia cultivar tifblue. Powderblue is an older NC State release. Some of the newer cultivars that I like Vernon is quite attractive fruit it will split in rainy weather. But I like the cultivar nonetheless. Krewer is a really new cultivar that I don’t know a whole lot about, but it’s large fruit, and quite attractive and flavorful.

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