#13 - Mar 2018 - Garden Stuff - © Sandy Lang - slang@xtra.co.nz
PHENOLOGY March: Autumn now. An odd spring. An odd summer. Harvest time for many trees and vines. Some are doing really well, but others really badly.
Yields: I read recently 40% of NZ olive groves will have no harvest at all this year - a really bad year. Commercial apple crops also vary widely year by year, with yields in good years being about twice those in bad ones. The same with wine grapes where good-year yields of 14 ton/ha, drop to 7 ton/ha in bad years. These values are national averages, not local problems. Some groves/orchards/vineyards fare much worse...! With this variability, commercial growers find it hard to manage cash flows and markets. But why are fruit crops so variable…?
Phenology: It’s to do with plant phenology - the study of life-cycle stages and how these are affected by the weather.
Apples: An apple tree flowers for three weeks. Each flower lasts three days. For every 100 flowers, only 50 form tiny fruitlets (fruit set). The rest fall off. Then, over the next six weeks about 40 of these remaining fruitlets fall off too. This leaves about 10 fruitlets (of the original 100 flowers) to grow to maturity.
This is still too many to get good-sized, export-grade fruit, so growers remove about 9 to leave just 1. This way only about 1% of apple flowers make it through to ‘applehood’. This high redundancy increases apple tree resilience to bad weather that can mess up flowering, or pollination, or fruit-set, or fruit development.
Grapes: In grapes, the vine makes the ‘decision’ to flower about a year before the flowers even appear. So, for the 2018 grape crop, the vine’s decision about how much flower to produce was made in December 2016. Then, in December 2017, the flowers emerged, developed, were (wind, not bees) pollinated, were fertilised and the fruits set. Since then the fruit has been developing and in April 2018 it will be harvested. During this 16-month (Dec 16 to Apr 18) period there are some phenological stages when the weather doesn’t matter much - but there’re others when it really does matter.
Olives: The phenology of olives is much like grapes but the timings are different. The olive crop failure in May 2018 will likely be due to bad weather 15 months ago (they decided to produce few flowers) and then bad weather just before last Christmas (pollination and fruit set were reduced).
And, so we get good years and bad years… ___________________________________
PHENOLOGY March: Autumn now. An odd spring. An odd summer. Harvest time for many trees and vines. Some are doing really well, but others really badly.
Yields: I read recently 40% of NZ olive groves will have no harvest at all this year - a really bad year. Commercial apple crops also vary widely year by year, with yields in good years being about twice those in bad ones. The same with wine grapes where good-year yields of 14 ton/ha, drop to 7 ton/ha in bad years. These values are national averages, not local problems. Some groves/orchards/vineyards fare much worse...! With this variability, commercial growers find it hard to manage cash flows and markets. But why are fruit crops so variable…?
Phenology: It’s to do with plant phenology - the study of life-cycle stages and how these are affected by the weather.
Apples: An apple tree flowers for three weeks. Each flower lasts three days. For every 100 flowers, only 50 form tiny fruitlets (fruit set). The rest fall off. Then, over the next six weeks about 40 of these remaining fruitlets fall off too. This leaves about 10 fruitlets (of the original 100 flowers) to grow to maturity.
This is still too many to get good-sized, export-grade fruit, so growers remove about 9 to leave just 1. This way only about 1% of apple flowers make it through to ‘applehood’. This high redundancy increases apple tree resilience to bad weather that can mess up flowering, or pollination, or fruit-set, or fruit development.
Grapes: In grapes, the vine makes the ‘decision’ to flower about a year before the flowers even appear. So, for the 2018 grape crop, the vine’s decision about how much flower to produce was made in December 2016. Then, in December 2017, the flowers emerged, developed, were (wind, not bees) pollinated, were fertilised and the fruits set. Since then the fruit has been developing and in April 2018 it will be harvested. During this 16-month (Dec 16 to Apr 18) period there are some phenological stages when the weather doesn’t matter much - but there’re others when it really does matter.
Olives: The phenology of olives is much like grapes but the timings are different. The olive crop failure in May 2018 will likely be due to bad weather 15 months ago (they decided to produce few flowers) and then bad weather just before last Christmas (pollination and fruit set were reduced).
And, so we get good years and bad years… ___________________________________