360 



ARBORICULTURE 



ARBORICULTURE 



most readily acclimated if seed is secured from the dry 

 slopes of Colorado. The Lawson cypress (Chamsecy- 

 pan's Lawsoniana), with its graceful pendulous branches 

 and foliage, and the pyramidal Libocedrus decurrens are 

 unquestionably desirable additions to our ornamental 

 stock, while the sequoias, especially S. gigantea, the 

 big tree, seems not to be able to support persistently 

 our eastern climate. 



One important feature which enters into considera- 

 tion when grouping conifers is the relative endurance 

 of shade or tolerance which 

 the species exhibit, thereby 

 indicating their use in va- 

 rious positions. The yews 

 and firs are the most tole- 

 rant of shade, together 

 with the hemlocks; next 

 may be placed the spruces, 

 arbprvitae (Thuya), and 

 junipers, while the pines 

 are mostly intolerant of 

 shade, excepting the white 

 pine, which is the most 

 shade-enduring of the 



gines; the larch and the 

 aid cypress are the most 

 light-needing of all, and 

 will perish soon if placed 

 under the shade of any 

 other trees. All species, to 

 be sure, are capable of 

 more shade-endurance 

 when young and on deep, 

 moist soil. Their relative 

 shade-endurance under 

 the same conditions 

 remains, however, the 

 same, and may be studied 

 in the forest by observing 

 the density of the individual crowns, the capacity of 

 maintaining a thrifty foliage under the shade of dif- 

 ferent species, and especially of young plants to per- 

 sist in such shade. 



Propagation. 



Most conifers ripen then- fruit in the fall, September 

 to November, and are best gathered soon after or 

 before ripening. The pines require two years (some three 

 years) to mature their cones. White pines ripen frurt in 

 the first two weeks of September, and the cones open- 

 ing shed the seeds at once, the empty cones remain- 

 ing on the branches. The cones of the firs fall apart 

 upon ripening, hence must be gathered before being 

 quite ripe. Spruces and hemlocks shed seeds from tune 

 to time, opening and closing their cones according to 

 the weather through the winter into spring. Some 

 pines, like Pinus pungens and P. serotina, keep their 

 cones closed for years, and artificial heat must be 

 employed to make them open and give up their seed. 

 In gathering seeds for the trade, such artificial heat is 

 frequently applied with ' pines in specially con- 

 structed seed-roasters; such seed should be carefully 

 inspected, as it sometimes suffers from improper use of 

 the heat. 



The proportion of germinating seeds, and the vital- 

 ity, i.e., the ability of retaining germinative power, 

 varies greatly not only with the seasons in the same 

 species, but from species to species. 



The lowest germination percentage and vitality is 

 found in firs and larch, which show rarely more than 50 

 per cent of good seed, and soon lose their vitality, while 

 spruce and pine, when entirely fresh, may show as much 

 as 95 to 100 per cent germination, and retain vitality 

 for two to five years, losing each year a proportion, 

 Norway spruce five years old still having 10 per cent 

 germination. 



320. A "weeping" or drooping 

 form of Norway spruce. This 

 is a so-called horticultural va- 

 riety, to be planted only 

 sparingly. 



In trade, a germination percentage for spruce of 75 

 to 80; pine, 70 to 75; fir, 30 to 50; larch, 20 to 40, should 

 be acceptable. 



Seeds are best kept in a dry, cool garret in tight bags 

 or boxes, excluding the air as much as possible. 



All seeds require a short rest or after-ripening of two 

 to four weeks before they are ready to germinate, and 

 some, like the taxus and juniper, lie over, even in 

 nature, for a year or more before they germinate. The 

 latter should be prepared for sowing by macerating 

 them, and removing the pulp in hot water, then mixing 

 with sharp sand in bags, and by friction freeing the 

 seed from the pulp. 



In the seed-bed somewhat more care is required than 

 with most other species of trees. A thoroughly mellow, 

 well-pulverized seed-bed of light loamy sand, possibly 

 enriched with well-decomposed manure (cow-dung 

 better than horse-dung) is required, the covering of 

 the seed varying, according to size, from a mere sprink- 

 ling for larch to % inch for the heavy-seeded pines. 

 They may be sown as soon as the weather is settled, in 

 northern latitudes the second or third week in May, 

 best in rows not more than 6 inches apart, and prefera- 

 bly in dry weather, when the soil does not clog, for 

 clogging or baking of the earth sometimes prevents 

 seeds from germinating. Mulch between the rows with 

 pine needles or sphagnum moss, or other fine mulch, 

 to reduce necessity of watering and weeding. Conifer 

 seeds need very little water for germination. The 

 seedlings, on the other hand, for the first three months, 

 until they have made their crown bud, need to be 

 either kept well watered or else protected against the 

 drying effects of sun and wind by shading, for which 

 purpose lath screens are best. These latter must be 

 lifted for airing after the sun is gone, especially in muggy 

 weather, to avoid damping-off. For wintering, a 

 covering with conifer branches or very clean meadow 

 hay is advisable (the latter is likely to bring in 

 weeds). 



For growing small quantities, the use of boxes, as 

 described by Jackson Dawson, of the Arnold Arbore- 

 tum, in Proceedings of the Massachusetts Horticultural 

 Society, is highly commendable. In well-drained boxes, 

 sow the seed soon after gathering, pile four or five deep 

 in a pit or sheltered place, cover with boards, and when 

 cold weather comes, cover up with leaves or hay. About 

 the middle of April, move them into a place where they 

 get the early morning sun. Keep the seedlings well 

 watered and free from weeds, and shaded as described. 

 Winter the seedlings in same manner as the seed-boxes, 



321. A "weeping" tree, representing a grotesque horticultural 

 variety. Ulmus scabra var. horizontalis. 



well covered up. They are ready for transplanting nex 

 spring, when they are making their first or second set 

 of true leaves. 



Since pine and spruce seedlings take about seven to 

 ten pounds of phosphoric acid, ten to twenty pounds of 

 potash and fifteen to thirty pounds of lime, besides 





