HYBRIDS OF THE LIVE 



OAK AND OVERCUP OAK 



Even the Forest Trees Hybridize and the Forestry of the Future May Have to 

 Take This Fact into Consideration 



H. Ness 



Horticulturist, Texas State Experiment Station 



IT LS a fact, long known to botanists, 

 that the systematic assignment of 

 several species of our American oaks 

 presents difficulties and doubts, be- 

 cause of variations that seem to confuse 

 the characters of some of the neighbor- 

 ing species. It is also well known that 

 several natural hybrids occur among the 

 oaks — the number of which would 

 certainly be greatly increased, if their 

 characters merged less with those of 

 one or the other of the parent species. 



In a little hybridizing work, which I 

 carried on with the Overcup Oak (Q. 

 lyrata) as father and the Live Oak (O. 

 Virginiana) as mother, I have become 

 impressed with the ease with which 

 fertile hybrids may arise between species 

 of oaks, even though the relationship be 

 apparently quite distant. These two 

 species agree in ripening their acorns in 

 one season, hence belong to the same 

 subdivision of the genus, which is called 

 Lepidobalanus. But there is still a 

 strong systematic difference, since they 

 belong to the opposite extremes of that 

 group of species. 



They differ widely in habit of growth, 

 in which Live Oak is characterized by 

 its low trunk and a broad, diffuse head 

 of rather crooked limbs and shoots; 

 while the Overcup Oak is of a tall, 

 pyramidal form with straight branches 

 and shoots. Its bark becomes strictly 

 flaky, characteristic of the true white 

 oak group, while in the Live Oak it 

 becomes rough and divided by fissures 

 into numerous narrow and irregular 

 ridges. The foliage of the Live Oak per- 

 sists throughout the winter until the 

 succeeding spring, while the Overcup 

 Oak is one of the first to shed its leaves 



in the fall. The texture of the foliage 

 in the Live Oak is strictly coriaceous; 

 the form of the leaves vary from oblong 

 to elliptical with entire or very remotely 

 repand margins. In the Overcup Oak 

 the leaves are four to five times larger 

 than in the Live Oak and more papery 

 texture, with deeply lyrately lobed in 

 margins. But the greatest differences 

 lie in the acorns and the cupules. In 

 the Overcup Oak, the acorn is oblate 

 and nearly covered by the cup, the scales 

 of which are much thickened on the 

 back. In the Live Oak the acorn is 

 ovate, projecting about two-thirds of its 

 length beyond that of the cupule, and 

 the scales are thin, with membranaceous 

 tips and margins. 



Cross pollination for my first hybrids 

 took place April 6, 1909, after all male 

 flowers on the mother trees and other 

 soak in their vicinity had withered — - 

 hence no danger of interference with the 

 cross-pollination. From this cross-pol- 

 lination nine acorns, of which three were 

 less than normal size, were obtained. 

 The seeds were planted in pots Novem- 

 ber 9 and gave rise to three young 

 hybrid oaks which were reared in the 

 nursery until March, 1912, when they 

 were planted where they could receive 

 the best care and observation. These 

 trees are, at the present writing, August 

 28, 1917, about 16 feet tall and with a 

 trunk diameter of about 5 inches, 1 

 foot from the ground. 



On April 14, 1910, a new set of cross- 

 pollinations were made, trees of the 

 same species being again mated in the 

 same order. The result of this is three 

 very vigorous specimens, planted on the 

 laws of the Experiment Station building 



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