170 



MEMOIRS OF THE NEW YORK BOTANICAL GARDEN 



year after year when all conditions, except opportunity for 

 cross-pollination, Avere liiglily favorable to fruit production. 

 Varieties like Harmon, Taft, and Fuerte have very generally 

 been shy bearers when grown alone or in solid blocks. Yet the 

 Trapp is one variety that has the reputation of being a rather 

 consistent bearer. Differences among varieties in ability to pro- 

 duce fruit to pollination within the variety are to be expected 

 from the marked differences seen in flower behavior. Local con- 

 ditions of Aveather may decidedly atfect fruit-setting through 

 influencing flower behavior and this may vary considerably in 

 different years. But the general experience has been that for 

 most varieties yields of fruit are frequently low whenever trees 

 of one variety are planted in solid blocks. 



The sole aim in interplanting avocados is to increase the 

 yields of fruit beyond that obtained or possible in solid block 

 plantings of single varieties. It can do this only to the extent 

 that it corrects faulty or inadequate pollination and to accom- 

 plish this at least three conditions must be satisfied.^ 



1. The interplanting must provide opportunity for an in- 

 crease in the number of proper pollinations that are possible. 

 This opportunity is provided for when trees that are normally 

 female in the morning are interplanted with trees that are male 

 in the forenoon, i^rovided, of course, that they bloom together 

 for a considerable span of calendar dates. A further selection 

 may be necessary in those cases in which the daily periods are 

 characteristically early or late (see charts 1-4). 



2. Means for effecting pollination must be provided and must 

 be in operation year after year. Insects are without doubt the 

 natural agents for the pollination of avocados. Honey bees are 

 fond of avocado nectar, they freely visit the flowers during both 

 periods of their opening, and Avhen their hives are in the vicinity 

 of avocado trees they are frequently seen in great numbers Avork- 

 ing among aA^ocado flowers. But for an insect to effect cross- 

 pollination it must repeatedly fly back and forth from one 

 variety Avhose floAvers are shedding pollen to another Avliose 



3 A more complete discussion of interplanting has previously been printed (Stout, 

 1925) and also reprinted in a later paper (Stout and Savage, 1925). This matter 

 will therefore only be briefly summarized here. 



