ANNUAL REPORT, 1946-47 55 



Spraying small weeds is more effective and cheaper than spraying large weeds. 

 The small weeds are killed more quicklj'; there is less risk of injury to the plants 

 since the spray is kept close to the ground; less material is used; and it takes less 

 time to spray a given area. 



Late fall spraying of grass weeds which winter over reduces the number of such 

 weeds in the spring. 



To the list of narrow-leaved evergreens which are highly tolerant can be added 

 mugho pine. Less tolerant is the Greek juniper, Juniperus excelsa striata. 



Study of Herbaceous Perennial MateriaL (C. J. Gilgut, Waltham.) Fifty 

 varieties of plants in the perennial test gardens did not survive the winter. Of 

 these, sixteen were so-called "hardy chrysanthemums," and it is increasingly 

 evident that most chrysanthemums are not reliably hardy here when not pro- 

 tected by mulch or wintered in a cold frame. 



Few replacements have been made and no new plants acquired because the 

 gardens are to be moved to another location to make way for the new laboratory 

 and administration building. The preparation of the new location — clearing, 

 grading, laying out of beds, and seeding of walks — is slowly being finished and it 

 is hoped that by fall many of the plants will have been moved in from the old 

 garden. 



The collection of American and English hybrid delphinium — among them Gold 

 Medal Hybrids, the color series of Giant Pacific hybrids, Wrexham hjbrids, and 

 Blackmore and Langdon hybrids — made good growth and an excellent display 

 in the spring. The Giant Pacific hybrids were awarded the L. H. Leonian Memo- 

 rial Cup for excellence by the American Delphinium Society', and a cultural cer- 

 tificate and silver medal by the Massachusetts Horticultural Societ}^ 



The phlox collection of varieties in commerce is not yet complete, but it is 

 apparent that some are not true to name and several are being sold under dif- 

 ferent names. 



Factors influencing the Rapidity of Growth of Nursery Stocl<. (C. J. Gilgut, 

 Waltham.) 



Rhododendron Leaf Bud Cuttings. Leaf bud cuttings of 30 named varieties of 

 hybrid rhododendrons taken in November, and again in February, treated with 

 the more common root-inducing substances in liquid and powder form, and 

 placed in various propagating media in the greenhouse failed to root. A few 

 w^ere still alive in June. 



Effect of pH and Nitrogen, Phosphorus, and Potash on Growth of Yews. It is a 

 common belief among some nurserymen that yews grow better at a pH above 

 5.8. When the pH of unfertilized field soil was adjusted at pH 4.5, 5.0, and 7.0 

 there was no appreciable difference in the growth of rooted cuttings of Taxus 

 media hicksi and Taxus cuspidata nana during the first season. 



These varieties grew equally well in unfertilized field soil and in field soil 

 treated so that (1) the nitrogen, the phosphorus, or the potash was high; (2) the 

 nitrogen and phosphorus, the nitrogen and potash, or the phosphorus and potash 

 were high or (3) the nitrogen, phosphorus, and potash were high. 



