~Varieties~--Mr. Stoke considers Bedford, Broadview and Lancaster best under his conditions. Mr. Becker's choice is McDermid but he thinks Crath No. 1 a potential commercial variety. Mr. Oakes likes Crath No. 1 and Ill. No. 3. Mr. Etter lists Burtner and Alleman as his best varieties. Mr. Fateley especially favors one tree because of nut and bearing qualities. Other growers have not as yet evaluated their varieties.
~Hardiness~--Only several growers in the colder regions felt that lack of winter hardiness was a serious limiting factor with their varieties. Those with winter temperatures ranging from 10 to 23 degrees below zero report little damage. Spring frosts are serious to many, especially in the southern states.
~Pests~--Several insects causing damage to Persian walnut were reported. The butternut curculio was most frequently mentioned. Others included leaf hoppers, tent caterpillars, and husk maggots. Few effective control measures have been developed. Squirrels are an ever present threat to nut crops in some localities, as are blackbirds.
~Cultural Practices~--Most growers apply varying amounts of fertilizer or manure to their trees in some form or other. Few mulch their trees. All do some pruning, mainly of a corrective nature.
~Pollination~--Most growers agree that usually, but not always, pistillate flowers are produced several years before the occurrence of catkins. Generally, Persian varieties do not adequately pollinate themselves but exceptions are reported. The problem is one of variable dichogamy. Some varieties shed pollen before pistillate flowers are receptive; others shed pollen when pistillate flowers are no longer receptive. This unfortunate situation probably explains the low yields experienced by some growers. Mr. Stoke lists the flowering dates of 13 varieties in the 1942 NNGA Annual Report which clearly illustrates dichogamy in Persian walnut.
Some varieties are considered sufficiently self-pollinating to produce at least light crops. However, this may be influenced by weather conditions. During an unusually warm spring catkins develop more rapidly than terminal growth containing the pistillate flowers. Mr. Stoke reports that ~Bedford~ produces both flowers simultaneously and that ~Caesar~ is practically self-pollinating. Mr. Etter finds ~Burtner~ fully self-pollinating and ~Alleman~ partially. Mr. McKinster's tree is apparently self-pollinating.