HORTICULTURE 147 



POLLINATION IN ORCHARDS. 



Various Reasons Why Flowers Do Not Set. Fruit-growers have 

 seen trees which blossom full, but do not set a fair amount of fruit ; 

 many have found their orchards unprofitable for this reason. It is 

 a practical point to know the causes of this loss and the best way to 

 prevent it. In the first place, but a small percentage of the blossoms 

 set fruit, even in the most favorable seasons and with the most pro- 

 ductive varieties. In blossoming time a Japanese plum tree is a 

 mass of white, carrying scores of flowers on a single branch; yet 

 scarcely a dozen fruits may set on that twig, and some of those must 

 be removed or the tree will over-bear. The normal failure in the 

 setting of fruit blossoms may be due to a number of causes ; as poorly 

 nourished fruit-buds, lack of pollination, or winter injury to the 

 pistils which cannot be seen with the eye alone. It is usually a dis- 

 tinct advantage to the fruit-grower, as it saves thinning. 



The wholesale failure in the setting of fruit is often called self- 

 sterility. It must have other varieties near it in order to bear well. 

 But it appears that self-sterility in orchard fruits is often confused 

 with the unfruitfulness resulting from other causes. The influences 

 which sometimes make trees unfruitful, which are often confused 

 with the unfruitfulness resulting from self-sterility, are (1) heavy 

 wood growth, (2) the attack of fungi on the blossoms, (3) frosts, 

 (4) unfavorable weather during the blooming season. It should also 

 be said that a tree is not self-sterile when it does not blossom. Why 

 trees do not bloom is generally due to poor management. 



Blossoms May Drop Because of Heavy Wood Growth. Young 

 trees generally set little or no fruit the first few years, when they are 

 growing fast, although they may blossom full. With most varieties 

 this early dropping of the blossoms occurs only two or three seasons, 

 but Northern Spy and a few other varieties of apples are often un- 

 fruitful ten to thirteen years from this cause. Older trees may show 

 the same results if stimulated too highly with nitrogenous fertilizers. 

 The logical remedy is to check this excessive growth of wood by with- 

 holding nitrogen or by putting the orchard into sod for a few years. 



The direct cause of this unfruitfulness is not known. The 

 stamens and pistils are usually well developed and pollen may be pro- 

 duced in abundance. Since young trees drop their blossoms as badly 

 in a mixed orchard where other pollen is available, as when alone, 

 the trouble probably lies more with the pistils than with the pollen. 

 Up to this limit of excessive growth, there is a fairly constant rela- 

 tion between the vigor of a tree and its productiveness. Lack of vigor 

 causes much more unfruitfulness than excessive vigor. If a tree is 

 unhealthy or dying because of poor nourishment, few of its blossoms 

 are strong enough to set fruit. The same results may follow if the 

 tree is exhausted by over-bearing. 



Blossoms May Be Killed by Fungi. If the weather is warm and 

 wet in early spring, conditions are favorable for the growth of fungi 

 and it sometimes happens that fruit blossoms are "blasted" by the 

 early growth of these parasites. Wherever spraying is practiced faith- 

 fully, the killing of fruit blossoms by fungi need not occur, especially 



