What causes the dormancy period?

[Desolus]

Is it photoperiod, temperature, a simple unchanging hormone cycle related to flowering?

For that matter what causes the flowering cycle to start, is that photoperiod or temperature dependant?

If the flowering cycle is photoperiod like I'm assuming but the dormancy period is temperature related shouldn't vines grown on the equatior have back to back flowering cycles? Do they?

 

[Masbustelo]

I can't answer all these technical questions. I have read that in temperate regions grape growers get two harvests per year. Also if there is a dry and a rainy season, entering into the dry season the grapes are pruned and foliage is removed to trigger a winter type and fruiting cycle.

 

[Desolus]

Well that answers some questions for me, and also speaks to a more complex hormone system than I assumed was there. Thanks.

 

[Rice_Guy]

Is dormancy photoperiod, temperature, a simple unchanging hormone cycle related to flowering?

First there are several genera of grapes. Muscadine have different regulatory targets than hybrids from univ of Minnesota. Not all grapes are adapted to the same climate therefore the control paths will be different.
As a midwesterner many crops are photoperiod responsive, they fruit at normal time for the variety but A long warm fall or protected geography will allow longer ripening with higher sugar. We see a temperature effect also. Grapes will “harden off” as they are exposed to lower temperature and winter hardiness (measured by lowest temperature) will increase as they are exposed to cold in December an then January. However if we have a warm spell as in January 2018 our grapes will start to break dormancy (lose absolute winter hardiness) and we suffer bud loss and reduced crop on varieties that should survive a specific temperature.
All in all the system is complicated and folks in the horticulture department are working on the chemical processes so that they can manipulate them. Cornell publishes a lot and reviews current research. U Min seems to publish less but profs are willing to talk about what they have found.
Dormancy existed in the cereal crops. One could plant them but they would not sprout till that effect was over.

For that matter what causes the flowering cycle to start, is that photoperiod or temperature dependant?

Flowering can have a temperature effect which is usually expressed as requiring so many degree days of chill to produce a crop. (Cherries, peaches . . . ) Specific to Midwest grapes, breeders don’t advertise varieties based on this trait. We seem to have photoperiod responsive hybrids. There is what I would call “being adult” buds on second year wood followed by shoots followed by flower clusters followed by flowers opening then fertilization then berry growth. NOTE Midwest grapes produce on second year wood so we are limited to once a season, , ,(however an unknown genera of patio grape claims to fruit all season). Cold will slow the rate of becoming adult (and heat in March will speed the sequential process). Nursery advertising is stated as, new variety X is a week earlier or later relative to old variety.

The system is complicated, , and confusing, , which genera were you asking about ?

 

[Desolus]

Thanks, that helped a lot. I still haven't settled on a variety, but I am intending on green house growing. As you can tell I really am going into this knowing next to nothing about it so every small piece of info helps bunches. Now I can search for some of the right things when looking at grape varieties.

My pourpose is only Homebrewing, and grapes will most likely be the primary sugar source for only a few batches a year. But I have grown very fond of adding grape extracts to my meads. I keep bees, grow berries, have fruit trees, so why not set up a green house for grapes as well?

The only real reason I prefer green houses is the longer period I get of vegitative growth, and pest control, mostly pest control. I wouldn't get a single fruit from a tree without a hard enclosure due to the deer around here.

 

[Rice_Guy]

Thanks, that helped a lot. I still haven't settled on a variety, but I am intending on green house growing.

In the early days of hybridizing some European vinifera (ie not cold tolerant) were green house grown for the purpose of having pollen to cross with american Rapara varieties which are Midwest cold tolerant. The greenhouse mainly kept peak lows to where vinifera could survive winter, not heated for year long growing.

Hum? ? Most folks chose flavor of grape variety

 

[Desolus]

Practical question: I've read that nodes older than 2 years will not flower, is this true for all varieties?

Impractical curiosity: any idea why that is?

 

[Rice_Guy]

question: I've read that nodes older than 2 years will not flower, is this true for all varieties?

You ask interesting questions. Yes, why are folks fertile from teenage to about when they are called grandma?
Many fruit crops produce on two year old wood. Raspberries, apples, grapes.
The referenced catalogue variety “pixie patio grape” would be what is called everbearing and is competent to fruit on new wood, likewise for everbearing raspberries which actually produce on old wood in early summer and on new wood in fall, or if they are mowed flat they will fruit late summer . . . . all in all there is a level of maturity of wood required for fruiting age. The horticulture folks probably have varieties which break the rules.

Specific for your greenhouse operation, expect that the everbearing crops are not equal, expect that the early or traditional crop will have higher sugar and fruit flavor, expect that the second crop is struggling for energy and less flavorful, you can improve the crop flavor by adding external energy. This is where the economists come in, with today’s pricing structure it is cheaper to put flowers or fruit on an airplane than to greenhouse grow up north. Yes I have a banana in the house but mostly as a momento of when I had that plant outside in a flower bed. Midwest grown bananas are lacking.

 

[balatonwine]

Practical question: I've read that nodes older than 2 years will not flower, is this true for all varieties?

Impractical curiosity: any idea why that is?

Grape nodes/buds are only for one season and are on last year's growth only. So not sure I understand your question.

Meanwhile, all my vinifera will happily grow new shots and fruit from 50 year old wood. In fact, due to a wet cool spring I have been removing so much such growth for the past month, low on the trunk, I can not keep up with it. And, yes, some have already tried to flower and set fruit.

In fact, I headed (cut off many vines) this spring to adjust the training method and many are bearing fruit from the old wood below the cut. Grapes are an amazing plant.

 

[Desolus]

@Rice_Guy
That's pretty awesome. And thanks for indulging my curiosity.

I think I'm going to purchase a few zinfandels, I like the variety of things you can do with a high sugar content.

@balatonwine
My question wasn't if old nodes could make new nodes, but if old nodes could flower in some varieties, which it turns out they can in some.