What is the effect of altitude on grapevine productivity?
1 What is the effect, if any of a potted grapevine being placed in the ground in Summer and not during Spring in the tropics?
2 If mature vines that were pruned in late winter months show no sign of inflorescence to date in June, does this mean that there will be no bearing this season?
3 The grape farm that sold me the seedlings 7 years ago has already seen their harvest, but is located at roughly sea level which is 1200 ft below my location in Kingston, Jamaica; What is the effect of altitude on inflorescence?
Outside United States
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I have a few questions -
- What varieties are you growing?
- What is your minimum temperatures in the winter?
- How old are the grapevines?
- Have you harvested anything from these vines to this point?
In the subtropics or tropics, you can plant a potted grapevine at any point. However, grapevines are sensitive to photoperiod and as the days get shorter, it will set a terminal bud and stop it's terminal growth.
As for an inflorescence, I'm surprised that you don't have any in June - typically even with muscadine grapes the vines will bloom in May. Were there ever any signs of the inflorescences this year? What is your watering/fertilization regime like?
Typically, the higher a site is located, the more chill units it will receive, and depending upon your variety, this should be beneficial for growth and flower bud development. However, the higher a site is, the more delayed flowering and harvest may be despite a small difference in budbreak from a site that is lower. This is a good paper that may help with the explanation: http://onlinelibrary.wiley.com/doi/10.1111/j.1755-0238.2008.00006.x/full. There are a few other articles in Russian that we do not have a good translation for, nor access to.
So, you may still see flowering in the grapevine, with an extended ripening time and later harvest. Sorry I can't be of more help - there really is very little research on altitude and grape flowering, particularly in the tropics.
Thank you Dr. Olmstead for your response. Before I answer your questions, let me say I just got back results for a soil test and the PH value was 7.3. The N and P levels were within range but the Potash was at the upper limit. Just today I added Ammonium Sulphate at all the roots. The variety of grapes is mainly Cardinal and four of the vines are 7 years with others being 4 to 6 years. Low temperatures in the winter would be in the 78 deg F region. I have never seen any inflorescence whatsoever with these grapes, and as such there has never been a harvest.The farm from which I bought the seedlings is currently having a good harvest. Thanks again. Joshua.
Your soil samples and the pH sound fine - high K shouldn't prevent the formation of inflorescences. The best guess I have is that the temperature is preventing the formation of flower inflorescences, and there are several good articles on bud microclimate and fruitfulness. In some grape varieties, the higher the temperature during the spring, the fewer flower inflorescences there are. The ideal temperature for many of these CA varieties is around 25C. http://http//www.ajevonline.org/content/56/4/319.abstract?sid=1ed5afb0-7723-4948-9f01-ca65893aac2a.
Could you try a plant hormone, like cytokinins? Here is an article - http://aob.oxfordjournals.org/content/45/4/439.short, and you could work with your local university there to get the full article. We don't have access at University of Florida. The cytokinins may help the vine to develop flower inflorescences.