Mar 10, 2022

Modern apple rootstocks evaluated in Mid-Atlantic

A discussion held during the recent Mid-Atlantic Fruit & Vegetable Convention regarding apple rootstock selections pinpointed some preferences of regional growers.

The panelists taking part in the Feb. 1 discussion moved away from assessing the commonly used M.9 rootstock, reporting on their success with G.11 and Bud 9 rootstocks, but acknowledged that even those modern drawing rootstocks have their own challenges.

At Terhune Orchards in Princeton, New Jersey, grower Gary Mount (pictured above, far right) has used B.9.

Cropping that variety too soon can lead to some complications, Mount said. Mount has turned to using G.11, which he has found to be similar, but has a stronger root for him.

“The one we’ve really settled on for us is B.9,” Mount said. “You have a little bit of a problem if you overcrop it too soon on a few of the varieties. If that’s a problem, we’ve gone to G.11, which is a very similar rootstock and has a stronger root.

“Way back when we went with pick-your-own, we wanted everything close to the ground,” Mount said. “We went with something small and B.9 was going to do it fine. Nowadays, we need the production and we want the trees taller. But I’m not having any trouble with the B-9s getting up there. I think it has something to do with southern New Jersey, which is a little bit more moderate in climate. Things seem to grow a little taller. Some of my friends in other areas have seen the B.9s in their orchards and they just don’t get up there and go.”

At 78 Acres in Smithburg, Maryland, grower Matt Harsh (pictured at top of page, second from right) offered a somewhat contrary opinion. He likes G.11, and voiced disappointment in B.9, along with other growers in his vicinity.

“It just doesn’t have enough horsepower. We just feel like it’s not the one for our location,” he said.

“We’ve planted just about all of these rootstocks,” Harsh said. “We’ve planted M.9, 337, Bud 9, G.11, G. 41 and we’ve recently planted some Bud 10s. My favorite so far, and the one I feel we’ve had the most success with is G.11.

“If there’s nothing else you take away from this talk here, you really have to figure out what works for you and your site, Harsh said. “If you haven’t planted any of these things, go to a nursery, order some trees and just throw them in the ground and take a look at them. Until you’ve seen them at your site, and cropped them yourself, you really don’t know what you’re dealing with.

Bud 9 for Smithsburg just isn’t quite the right rootstock. It just doesn’t have enough power. I just feel like it’s not the right one in our area. That’s not just me, other guys in our area have said the same thing. G.11 has its limitations, but for us that’s been the best one so far.”

Bud 9-Honeycrisp combo works

“The Bud 9 Honeycrisp thing is very well established,” Harsh said. “There’s research behind that. We have that combination and it definitely works. We’ve planted ours at 2.5 by 12 feet. If we were doing it again, I’d probably plant them at 18 inches by 10 or nine (feet). You can put those things so close together, and they probably still will not be close enough together. It is the thing to grow Honeycrisp on and everybody knows that.

“We put ours on 10-foot poles, mostly because I didn’t think they’d get that tall, and also because I couldn’t get 12s that year,” he said. “The 10s are the thing, at least at our site, because they’re never going to get to a 12-foot pole.

To avoid the temptation to save fruit, Harsh said he removes the apples with chemical spray rather than hand culling. His spray regime usually takes place at 4 a.m.

“It is very hard to be disciplined enough to get the fruit off those things early,” Harsh said. “The best thing I’ve come up with for taking apples off the trees is just spray them off. Don’t go out there and do them with your hands. Just take that option completely off the table. When they’re in bloom, go out there and hit them with ATS (ammonium thiosulfate). Just take them off. Then you can’t be tempted to leave the fruit.

“We have a lot of Premier Honeycrisp that we’ve planted on G.11. I really like that combination,” Harsh said. “The G.11 gives you just a little more horsepower for the Honeycrisp. Premier and regular Honeycrisp are just not the same thing. They are different apples, for sure. We get decent color and really good fruit size on a really nice tree with the G.11, Premier combination.”

G.11 aids production

Blake Slaybaugh (pictured at top, second from left) of Mountain Ridge Farms in Biglerville, Pennsylvania, leans toward the G.11 rootstock. He said it produces branches at convenient crotch angles for orchard production. Slaybugh has found G. 41 to be a more difficult tree to manage in an orchard because it grows higher and tighter than G. 11.

“We haven’t really planted anything too new. We’ve planted a lot of Geneva’s, 41s, 935s, some Bud 10,” Slaybaugh said. “It is very site-specific and depends on horticultural practices. Bud 9 on 10- by two-foot spacings work very well if you prune them back and things like that. If you are going into a 15- by five-foot planting, one where there’s so much space, a Bud 9 can’t do that. We’re looking at Bud 10. We’ve a lot of Fuji that work really good. We’re kind of a little scared on yield efficiency, but we’ll see. We definitely kind of steer away from B.11.

“We plant a fair amount of G.41s and 935s,” Slaybaugh said. “About three to four years ago, roughly 40% failed. We have pretty different minds on G.41s and 935s. I will probably plant them again at Mountain Ridge Farms. That’s probably something we will not continue. I don’t see enough benefit, either. The ones that did live didn’t produce to what a regular 337 or M.29, to be honest with you. So why pay extra for it?

“Bud 9 on Honeycrisp is a great combination,” Slaybaugh said. “It keeps it timid and everything in check, with great color. Bud 10 might be better if you’re looking for a more medium-sized fruit for Honeycrisp and Evercrisp.

“Gala is something we’re still trying to work on,” he said. “We definitely want to get one size bigger. Is keeping with 337 the way we want to go or Bud 10 with Gala? I think Bud 10 in Gala could be pretty good. That’s definitely what we’re seeing.”

G.41 presents obstacles because it generally arrives from the nursery without roots, along with having brittle wood that makes grafting a challenge. Harsh said despite wondering “how in the world is this tree going to survive?,” they do manage to flourish but are not moveable once they are grafted.

Select rootstock by location

By staking G.41 when it’s planted, Jason Mattson (pictured at top of page, far left) of Saunders Brothers orchard and nursery in Nelson County, Virginia, about 30 miles south of Charlottesville, has found it works better when tying both the rootstock and scion when using a vertical post.

Without that security, “the wind can blow it, and you can lose a bunch of trees,” he said.

Bud 9 and Bud 10 work well when growing bitter pit-susceptible varieties such as Honeycrisp, Mattson said.

The key is not allowing those trees to produce a big crop early on. The fruit should be stripped off for the first three to four years in order to allow the tree to fill its space.

“If you’re going to grow Honeycrisp on a Bud 9, just be ready to be patient,” Mattson said.

“There’s a lot of new rootstocks out, but you really want to find one that suits your soils and your growing conditions the best. The new roots that we’ve planted in our orchards include the M.9 clones. We’ve done some Bud 9. We’ve done quite a bit of G.11 and G.41. I think all in all, G.11 is probably the one I’m leaning toward.

“There are some varieties I have some hesitancies about,” Mattson said. “I think the M.9 is sort of the perfect tree we’re all looking for in size, structure and just wants to bear fruit. But, there’s some other concerns in that, at least early on. I’ve had some decline in that root. All in all, I think the G.11 is the one performing the best and is the one I’m comfortable planting large blocks of right now.

“The Bud 9, Bud 10 seem to be a really good combination for Honeycrisp, Evercrisp, Jonagold – any of those bitter pit-prone varieties,” Mattson said. “They really give you a superior apple quality. You really have to be cautious about that variety early on. You don’t want to fruit it heavy, especially with Honeycrisp. You want to strip the fruit off those trees, especially the first three to four years or you won’t ever get to fill that space. At least that’s how it is for my growing region. You have to go into it with your eyes wide open and be aware of what you’re getting into.

“If you’re putting Honeycrisp on a Bud 9, be patient and strip the fruit off of there the first three to four years and then you should be able to fill your space. I like M.26 in Gala,” Mattson said. “I don’t have any of those growing in my orchard right now, but just looking at what other growers are doing, it’s been a good experience. I think that’s a really good rootstock combination for Gala. Although, it seems like more and more M.26 might be a little bit harder to find.

“G.41, in general, in our area seems to be compatible with just about anything we’re trying to grow – whether it’s Ambrosia, Crimson Crisp or Evercrisp – it does well on it. I have no hesitation about those combinations.”

All about support

The consensus of the panel members from four different Mid-Atlantic states was that whatever modern rootstock is used in an orchard, it most likely will need support from posts and wires. Doing that work can be difficult and tedious.

Harsh said he uses a post pounder to set the posts.

“The first time you see that thing put those 12-foot poles in, it’s just like a miracle,” Harsh said. “All of a sudden I can do this.”

Suckers produced by the rootstocks also need to be addressed. Mount said he has his crew cut off the suckers in the offseason as early as November.

“It kind of ticks me off that it takes so long, but that’s the way it is,” Mount said.

Mattson tried to use glufosinate to manage root suckers, but no longer takes that approach because he lost some trees doing it that way.

He now prunes root suckers when the regular orchard pruning is conducted.

Mattson still does trim his Asian pears prior to dormancy because those trees produce thorns that become a management issue prior to the offseason.

— Gary Pullano, editor