You guys have me thinking with all your interstem threads…
We have a issue here in Phoenix with fall apples. Summer low chill apples tend to grow and fruit rather well on M111 but fall apples grow incredibly slow here. The issue is that all apples tend to go into a extended summer dormancy and quit growing from late May until late September. Now the low chill apples come out of dormancy early enough to get some decent growth in before summer dormancy hits. The fall apples are just coming out now (mid April) and have scant time to grow before they shut down. Its been proposed that its a rootstock issue and that the reduced vigor of M111 isnt pushing the trees hard enough to keep them going when the heat gets here. Our one really knowledgeable grower is now switching over to domestic seedling rootstock in the hopes that the extra vigor will keep things pushing longer into summer.
My big concern with DSR is that it will take a extended amount of time (5-10 years) to see fruit out of this understock. Could a DSR with a M111 interstem be the answer? Would this give us the vigor we need with the precocity we desire? What say you?
I only have a handful of interstem tress, some in ground for 3/4 years now. No none of them show much vigor compared to the many trees I have on seedling roots, but my environment is of course radically different than yours (we are northern vt mountains)
Along your line of reasoning another possibility presents itself. Planting grafted trees with the union below soil line.
Jim cummins suggested this to us when we were putting in the first of our plantings. It’s a fairly common practice in the north. Sometimes used to provide additional protection to a cold tender rootstock, but also used to increase vigor for short season growing (when you can’t find what you want on seedling)
The theory is that the tree establishes on it’s grafted roots, but then develops a dual root system once the scion roots in a few years later. When it works right, the tree starts to fruit about the same time those roots kick in. So you get reasonable precocity and reduced dwarfing.
But there are a number of variables. Most notable that not all scion send out advanticious roots readily. And the vigor of self rooted apples varies quite a bit in and of itself.
It also really helps if the tree was grafted very low to begin with, otherwise planting deep enough to bury union can really set them back.
On a few trees I have planted with union at or just below soil level, and then let wood hip mulch slowly creep up over the years. That has worked quite well. I have a tree on bud9 that acted as bud 9 should (small and early fruit) for the first five years, and then picked up vigor but also continued to fruit heavily.
Although this doesn’t really answer your question (since it’s probably impractical for growers, although for someone growing a couple of trees in his or her backyard it wouldn’t be as hard), I’ll toss out the idea of using shade cloth or something similar during summer.
I’ve heard of people in Arizona growing cooler weather crops (e.g., lettuce, broccoli) successfully during summer using shade cloth (note that’s IIRC - it might have been something similar to regular shade cloth but not the same thing).
If one had something that would reduce the ambient light by, say, 50%, it might be quite helpful. If it also reflected IR light (the type that’s most responsible for heating things up) or could be combined with something that reflected IR light but let visible light through (photosynthesis uses part of the visible spectrum), that would have an even better chance of being helpful.
This is my gut feel / scientific wild guess so don’t take it as gospel - just as something very speculative to look into if you think the idea might have merit.
Talk to Fascist Nation. He posts here some but a lot on DWN forum. A very knowledgeable grower in Phoenix and very helpful.
I didnt ask a Arizona source because I didnt want a Arizona answer. There is no one here with interstem experience.
@Windfall_rob that is a terribly interesting concept. Thank you for bringing it up! Will have to roll that around in my mind.
Ya but he might tell you that shade is the only solution. That’s what I’d suspect. I’d put up 40-50% shade cloth on west and top side of apples. I think it would help here and I’ve never seen warmer than 102F.
Another thing that will help AZ apples even at 4500 ft elev is a grass ground cover to help cool the air. Learned that on an apple tour near Bisbee I think. The mist coolers would probably be even better. But are apples worth all that trouble, not to me.
The other thing to remember is that much of the apple issue in warmer areas of AZ is lack of chilling. This delays and reduces foliation no matter what the summer is like. I get several times as much cold here and it’s still an issue. The higher chill apples just don’t grow much with minimal chilling.
Im really not a apple fan. If were up to me id just live with out fall apples and be happy with our standard summer apples that do fantastically well here. Tropic sweet especially is a very good summer apple that works very well here. The issue is that people wont hardly buy a apple in July. They are programed to think Fall=apples. So im working to see what is possible. We grow fall bearing pears and it is a beautiful thing to have fruit that refrigerate well and give us something to sell October-January when we have no other fruit. So its worth a little experimentation and risk to crack this nut.
There are lower chill fall apples that fall within the chilling we get. I really dont believe that is the issue. I believe it to simply be a environmental factor of coming out of dormancy too late for our spring and the vigor not being enough on M111 to push growth thru the heat of the on coming summer. We have no university research being done here on such things. Its up to hobbyists to try to work this out if it can be. We are putting in gala, pink lady, sundowner, fuju, and possibly granny smith this fall on full size full vigor rootstock so hopefully within a few years we should know something.
They come out of dormancy late because they don’t get enough chilling. That’s the one and only reason they are late. Those apples you mention will grow and produce under low chill conditions but they’re very unhappy about it. They need 1200-1500 hrs to really surge out of the gate in spring. The leaf buds need chilling just as much as fruit buds and often need more.
Apples are much more forgiving than many fruits. Most apples would like that 1500 hrs but will survive and produce on much less. Many other fruits aren’t nearly as forgiving and some fall in between. Northern high bush blueberries are extremely unforgiving. Peaches and nectarine are in between.
Then add on your extreme summer heat and “high” chill apples are struggling all summer.
Alright, alright! But im still gonna try it. lol Nothing ventured nothing gained!
I was just rereading a old cloudforest thread on apples and chill. It makes your point quite clearly. Thanks for letting me bash my head against the the truth a little. We have a pink lady and a winter banana in the ground for year that just doesnt do anything. I got it in my head that it was because of rootstock but your right, its a chill issue. And I see from the old cloudforest thread that your advice of shade is also right on. Im just not willing to shade them so I believe that I will shift my gaze. Instead of apples I think I might seek out some pears that may fit the slot better. We already have one large fall pear that is quite productive, I believe it to be a kiefer. Do you have any experience with other lower chill pears that might be productive for us @fruitnut? Im seeing that southern bartlett, southern king, Monterrey, Orient, Moonglow are all proven low chill. Anyone have and feedback on taste quality of them?
I’m not much help on low chill pears. Hopefully someone else can help you.
Consider Tennosui. Not sure of its chill requirements, but originated in TX.