Citrus Growers Forum

danero2004 · Posted: Mon 02 May, 2011 6:39 pm

So by making him believe it is spring , by putting it to some cold temps , will force flower buds to form?

grad85 · Posted: Mon 02 May, 2011 7:45 pm

Interesting artikel.
Millet it,s password protected, that,s i think the reason you cannot link it.

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ivica · Posted: Mon 02 May, 2011 8:00 pm

danero2004 wrote:

So by making him believe it is spring , by putting it to some cold temps , will force flower buds to form?

Maybe

Quite general and recent article:
Wilkie et al., 2008., "Regulation of floral initiation in horticultural trees" http://jxb.oxfordjournals.org/content/59/12/3215.full
a lot of interesting findings, like
"In citrus, in contrast, leaves are not necessary for floral initiation in cool inductive temperatures (Davenport, 2000) or for floral induction via water stress (Southwick and Davenport, 1986), indicating that both the cold temperature and water stress stimuli that induce flowering may be perceived in the stem or buds."
or
"The need for carbohydrates for floral initiation has often been investigated by measuring levels of stored carbohydrates, or imposing treatments such as girdling that modify the levels of stored carbohydrates, and correlating these with flowering intensity. The results have been mixed. Girdling increased flowering intensity in olive (Lavee et al., 1983), lychee (Menzel and Simpson, 1987), and citrus (Goldschmidt et al., 1985) indicating increased stored carbohydrates can increase floral initiation, because girdling has been reported to increase levels of stored carbohydrates in some horticultural trees (Goldschmidt et al., 1985; Menzel et al., 1995). Further, a study of stored carbohydrates in biennial bearing citrus found that high and low levels of stored carbohydrates corresponded with high and low levels of floral initiation, respectively (Goldschmidt and Golomb, 1982). However, other experiments with citrus have revealed complex interactions between cool inductive temperatures, PGRs, fruit load, and girdling treatments on the flowering intensity (Goldschmidt et al., 1985)."
etc., and a lot of references for further read,
also The Flowering Newsletter http://www.lancs.ac.uk/other/bsajxb/
and Special Issue: Major Themes in Flowering Research http://jxb.oxfordjournals.org/content/57/13.toc

Unshiu related:
Yahata et al., 2006., "The Effect of the Time of Fruit Harvest on Flower Formation and Carbohydrate Contents in Shoots of Wase Satsuma Mandarin Trees" http://www.jstage.jst.go.jp/article/jjshs/75/1/75_32/_article
Garcia-Luis et al., 1986.,"Inhibition of flowering in vivo by existing fruits and applied growth regulators in Citrus Unshiu", abstract at http://onlinelibrary.wiley.com/doi/10.1111/j.1399-3054.1986.tb05960.x/abstract

Millet's link is here:
http://www.fshs.org/Proceedings/Password%20Protected/1936%20Vol.%2049/45-49%20(ABBOTT).pdf
Clicking on the link will not give you desired content (faulty parsing), copy/paste the whole line in Address bar and press Enter.

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Millet · Posted: Tue 03 May, 2011 1:03 am

Carbohydrates are involved, but I think what is also further involved is actually the carbohydrate/nitrogen ratio. - Millet (624-)

serj · Posted: Sat 24 Dec, 2011 5:28 pm

Hello! I have some idea about not-blooming my satsuma citrus. I have about -0.1 -0.5 C (by celsius) in the my greenhouse in late winter and early spring. I think the low temperature can kill the flower buds. I'm right or i'm mistaken?

Laaz · Posted: Sat 24 Dec, 2011 10:00 pm

You would not want the flower buds exposed to freezing temps although I have had frosts many times with flower buds on the tree & they were fine. A hard freeze will kill them, but I doubt you get a hard freeze in the greenhouse.

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serj · Posted: Sun 25 Dec, 2011 2:28 pm

Laaz, can not-blooming of my citrus be affected by the low temperature during last winter month? It was about +0,5 +1,5 C for the last month (from the 10.02 till 11.03)? Can the flower bud be killed by the temperature about -0,1 C during 3 days?
I find the citrus that i took off from the greenhouse in my house is blooming. I think it something happened to the my citrus in the tranch from the low temperature +0,5 +1 C.

Laaz · Posted: Sun 25 Dec, 2011 3:07 pm

Your satsumas should not be blooming this early. Although I don't have any in containers, mine bloom in early March.

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Millet · Posted: Sun 25 Dec, 2011 4:56 pm

serj, your satsuma trees did not have any flower buds to freeze. Citrus trees do not form early flower buds (pre-season flower buds) like apples do. Citrus form, actually differentiate, flower buds from the foliage buds, at the time of the new flush. I will promulgate only a guess, as I do not know what environment your satsumas went through prior to the current flush. Citrus use carbohydrates (sugars) in the process of differentiating flower buds. This requires carbohydrates (sugars). Sugar production in citrus comes from photosynthesis of CO2 and light. In a covered trench greenhouse, did your trees receive plenty of air movement and good light penetration to enable your trees to manufacture the required sugars? This above is only a guess of a possible cause. Merry Christmas. - Millet (386 ABO-)

serj · Posted: Sun 25 Dec, 2011 5:29 pm

There are no light when trench is covered, all plants sleep. But in spring my trench is opened and light is enough for growth and blooming. Some citrus blooming well - orange, clementine, calamondine. But canton lemon had only 2 flower buds, two satsuma tree didn't bloom. A month ago i move canton lemon from the my trench to the room and it start to bloom. one grafting of my satsuma tree start to bloom too. The scion was taken 1,5 month ago.

Paul · Posted: Sat 31 Dec, 2011 8:36 am

You may need to spray the plants in the greenhouse in late winter or early spring fertilizer with a predominance of phosphorus, or it does not help?

Millet · Posted: Sat 31 Dec, 2011 5:10 pm

Actually, mostly urea but also potassium nitrate can be used used as a foliage spray, to aid in the development of spring blossoms on citrus. The spray is applied 1-2 months prior to the tree's anticipated blooming period. - Millet (380 ABO-)

serj · Posted: Wed 04 Jan, 2012 5:58 pm

I'm confused what can i use as foliage spray: potassium nitrate or phosphorus?

Millet · Posted: Wed 04 Jan, 2012 7:15 pm

The vast majority of commercial growers use the less expensive urea spray, a month or two prior to the expected bloom date. Potassium nitrate, which is higher in cost, can also be used. I know of no one that uses phosphorous, for this purpose. - Millet (376 - ABO-)