Crosses made between filberts and hazels usually produce great changes in the resulting fruit.  J. F. Jones won considerable horticultural fame from crosses he made between the wild American hazel known as the Rush hazel, and such varieties of the European filbert as the Italian Red and Daviana.  Hazel and filbert cross readily and the resulting seedlings will usually bear after only three or four years.  For both these reasons, they are good material for a beginner to work with.  If the wild hazel is to be used as the female, or mother, of the cross, it is necessary to pick off all the male blossoms, or staminate blooms.  This should be done long before they begin to expand.  The pistillate, or female blossoms, should be enclosed in bags, about six of the three-pound, common kraft bags should be enough.  These are slipped over those branches which bear female blossoms and are tied around a heavy packing of absorbent cotton, which has been wound around the branch at approximately the place where the opening of the bag will be.  In fastening the mouth of the bag around the cotton, I find that No. 18 copper wire, wrapped several times around and the ends twisted together, is more satisfactory than string.  This makes a pollen-tight house for the pistillate blossoms but not one so air-tight as to cause any damage to either the plant or blossoms.

In order to have pollen available at the proper time, it is necessary to cut a few filbert branches which bear staminate blooms and store them in a dark, cold place to prevent the pollen from ripening too soon.  I recommend keeping such branches in dampened sphagnum moss until it is time for the pollen to ripen, or if a cold cellar is available, burying the cut ends of large branches carrying male catkins one foot deep in clean, moist sand.  When the pollen is wanted, the branches should be placed in a container of water and set near a window where sunlight will reach them.  Usually, after one day of exposure to bright sunlight, the staminate blooms will expand and begin to shed their pollen.  The pollen may easily be collected by allowing an extended catkin to droop inside a vial or test tube and then, as the catkin rests against its inner wall, tapping the outside of the tube sharply with a pencil to jar the pollen grains loose.  A separate test tube must be used for each variety of pollen to be experimented with.  By following this procedure for several days with all the staminate blooms that have been gathered, the experimenter should have enough pollen for work on a small scale.  The test tubes containing this pollen should never be stoppered with corks, but with plugs of absorbent cotton, which will allow the passage of air.  Pollen may be stored in this manner for several days, possibly as long as two weeks, if it is kept dry.  By a close observation of the blooming period of the wild hazels, one is able to determine the best time for placing the filbert pollen on the pistillate blossoms.