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  1. Why hand pollinate?
  2. When to pollinate
  3. Collecting pollen
  4. Applying pollen and marking flowers
  5. The effects flowering date has on pollination
  6. Pollination with female-stage pollen
  7. Natural pollination via insects
     
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  The effects flowering date has on pollination
 

Studies in New Zealand have shown cherimoya trees generally have a flowering period of two months, usually somewhere between December and February, with about 80% opening during the middle four weeks. There can be daily variations in flower numbers ranging from 0 to 100 per tree, with a total of approximately 1,000 flowers over the entire two months.

Pollen viability appears high, except at the start and end of flowering when lower viability can result in poor fruit set and retention. Fruit set in the middle period is generally high and a large percentage of flowers pollinated (50–90%) should produce fruit that will stay until harvest. Flowers should be pollinated regularly throughout the flowering peak to maximise crops of exportable fruit, with early and late opening flowers best avoided.

Flowers opening on cool nights (below 12ºC) and in low humidity can result in poor pollination and tend to produce few fruit.

The studies also showed pollination date has a big effect on the number and average weight of seeds in fruit. The average seed weight of 0.7g at the start of flowering can decrease to less than 0.2g at the end, which causes a drop in the average fruit weight as hormones released from seeds are essential for fruit growth. The later in the season flowers were pollinated, the more seeds the fruit contained. Fruit from flowers pollinated at the peak of flowering were found to have a desirable level of 11 seeds per 100g of flesh, compared with an unacceptably seedy 59 seeds in fruit from flowers pollinated at the end of flowering.

Cropping potential appears to be greatest in the third and fourth week during the flowering peak when flower numbers, fruit set and average fruit weight are highest. At the start of flowering, flower numbers and fruit set can be low, while at the end of flowering the average fruit weight, fruit set and a high seed content result in fruit of an undesirable quality caused by the decreasing average seed weight.

Though the flowers pollinated earliest give the earliest fruit, it’s usually less effective in terms of percentage of fruit set and size. However, the earliest fruit is most desirable because anticipation is greatest and prices are highest.

Potential cropping of cherimoya for each pollination day, from a study done in New Zealand on the White variety

Chart 1

Pollination
date
  Ripe male-
stage flowers
per tree
  Receptive female-
stage flowers
per tree
Fruit retention
of pollinated
flowers (%)

28 Dec   0   3 0
30 Dec   3   23 0
3 Jan   0   20 12
7 Jan 2 11 17
11 Jan 20 42 33
13 Jan 5 64 73
17 Jan 4 24 87
21 Jan   47   50 47
23 Jan 36 30 33
25 Jan 18 25 60
29 Jan 54 56 60
31 Jan 72 83 47
4 Feb 92 101 90
8 Feb 8 19 80
12 Feb 32 36 67
16 Feb 28 32 50
20 Feb 0 16 33


Chart 2

Pollination
date
  Average fruit
weight (g)
  Potential crop
(kg per tree)
Number of seeds
per 100g of flesh

28 Dec    
30 Dec    
3 Jan   607   1.5 16
7 Jan 578 1.2 13
11 Jan 726 10.1 10
13 Jan 742 34.8 9
17 Jan 659 13.9 10
21 Jan   204   4.8 11
23 Jan 357 3.5 12
25 Jan 594 8.9 14
29 Jan 343 11.5 16
31 Jan 296 11.6 19
4 Feb 325 29.3 23
8 Feb 337 5.1 29
12 Feb 199 4.8 34
16 Feb 156 2.5 40
20 Feb 162 0.9 51

In this study January 13 had the best overall results

The information for these charts has been collated from various articles published by ”The Orchardist of New Zealand“.
 
Next
– pollination with female-stage pollen

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Last modified 21/11/02