Ar:aL i, loiC) 



2P9 



GENERAL CORRESPONDENCE 



PERFECT POLLINATION OF CITRUS GROVES 



CV PI?OF. E. G. BALDWIN 



Your timely discussions of the proper 

 number of colonies to fertilize a citrus 

 grove, in various pages of Gleanings, have 

 greatly interested me. "While it does not 

 seem to be imperative to know liotv few eol- 

 omes will do the work, still it may be useful 

 on occasion; for it will often liappen, prob- 

 ably, that some groves will have a minimum 

 quota of colonies in their vicinity. In such 

 instances, if the number of colonies present 

 were below the accepted and proved mini- 

 mum, the owners of such groves could eas- 

 ily bring in sufficient to insure fullest fer- 

 tilization. So it is wise to discover, if pos- 

 sible, what number will do effective work, 

 where more can not be had. But I have al- 

 ways held, here, that " the more the bet- 

 ter," and that seem.s to be the idea that is 

 crystallizing in the minds of the growers 

 hereabout, and even further south, about 

 Bradentown, for example, and Tampa. 



The blossom of the citrus (orang'e or 

 grapefruit, for instance) is a so-called "per- 

 fect flower" — that is, has both pistils and 

 stamens on the same stem, more or less 

 united at their bas^es. The pistils inse a lit- 

 tle higher from the base than the envelop- 

 ing stamens, which stand outside of and 

 lower than the ]iistils. There ai'e, hence, 

 three ways in wliicli the blossom can be fruc- 

 tified — gravity, wind, and insects. Gravity 

 carries the dust from some stamen 

 above the particular blossom in question 

 down upon the pistils of the blossom below. 

 Wind carries the dust from other blossoms 

 on the same or neai'by trees, over upon the 

 pistils of blossoms within wafting distance. 

 One citrus tree usually has many blossoms 

 out at one time tho not with anytliing like 

 the same evenness as the blossoms on apple- 

 trees. The orange-blossoms come out much 

 more irregularly and far less simultaneous- 

 ly. Nearby trees also add their contingent 

 of fertile stamens to fertilize the pistils of 

 any trees that are near enough; therefore, 

 even were wind and gravity tlie only fertil- 

 izing media or agencies, there would be some 

 fmit, often heavy crops of it, from these 

 agencies alone. The fullness of the fertil- 

 izing would in all such instances depend on, 

 first, the fullness and evenness of the bloom 

 on the particular tree under consideration. 

 the proximity of other trees, and their si- 

 multaneous blossoming period, etc. ; second, 

 on the weather during the time of bloom. 



It is this latter point that we have studied 

 most carefully. In our latitude (29th de- 

 gi'ee) the citrus-blooming time is at the end 

 of February and thru March. In the lati- 

 tude of Tampa, for example, it is the latter 

 half of rebraaiy and early March. Our 

 conclusions are based largely for our per- 

 sonal deductions — that is, on data recorded 

 by us in and about Deland. Here we have 

 on an average, say, five weeks of blooming 

 time. That means that from the time the 

 earliest blossoms come out on the first and 

 most advanced trees and varieties (tanger- 

 ines are much later than other's), to the end 

 of the "last lingering rose" of the tangerine 

 blossom, on latest groves (and land and 

 location alter the time much), we have an 

 average of about a five-weeks' bloom-period. 

 That gives an outsider a very eiToneous 

 impression, I fear, about the length of 

 bloom of a single blossom. I have watched 

 this very carefully, and I think a blossom 

 seldom hangs on more than thr'ee days, on 

 an average. In hot dry weather one good 

 day of sun seems to " cook " it, and it is 

 done for the second day. For that partic- 

 ular blossom, then, the fertilization would 

 have to be done within about two days, say, 

 to be effective and best. Of course one day 

 is sufficient provided the pollen from some 

 stamen is wafted to the pistil in that time. 

 But a season of damp foggy weather, when 

 pollen wafts but little during the bloom of 

 the particular blossom, would likely prevent 

 full fructification of that blossom. A dead 

 calm, too, in that time, Avould make gr-a\'ity 

 the only means of fertilization. For such 

 blossoms as happened to come within the 

 wet or calm weather only, would fullest fer- 

 tilization be impossible. The succession of 

 blossoms on other stems of the same tree 

 would give opportunities for their fertili- 

 zation outside of the periods of calm or 

 dampness. But, taking our average springs 

 liere, one with another, we do not average 

 more than half the time really favorable 

 weather. Much is either damp, or a dead 

 calm. And were gi-avit^- and winds the only 

 agencies for fructification, we feel sui-e that 

 many blossoms would not be fertilized at 

 all. Of course, you may say that, usually, 

 every tree sets enough fruit to insure a 

 sufficient crop. But would it do so with 

 these two agencies alone? T must confess 

 that I am not in position to state dogmati- 



