500 



HORTICULTURE 



AprU 6. 1913 



Hardiness 



The reeeut sym^josiums lu Hokticulture on subjects 

 abstruse and otherwise and the interest manifested in the 

 same even to the West, lead me to again ask the ques- 

 tion, What constitutes hardiness in plants? Many years 

 ago I asked the same of the late Dr. George Thurber who, 

 in his day, was one who should know but he shook his 

 head. 



Probably it is a world-old question, for the caravans 

 that strewed the seeds of dried peaches along the trail 

 from China through Central Asia to Persia where for 

 many generations we supposed the peach was indigenous, 

 must have started people thinking thousands of years 

 ago, it being even then a question of having to eat to live. 



It is safe to say that there is no phase of gardening 

 that exercises the cultivator from one generation to 

 another quite as much as that of hardiness. We are 

 living it over again anew in the introductions of Wilson 

 from China, only a tithe of which are available to culti- 

 vators as yet. 



The most I have seen from investigations of scientists 

 is contained in the statement that "When the tempera- 

 ture goes below certain degrees of cold, the tissues of 

 some plants burst." This is a purely mechanical action 

 and we cannot derive much comfort from it. 



We will take the instance of the Douglas fir and Abies 

 coDColor. They occur both in California and Colorado; 

 seedlings raised from the last named State are hardy, but 

 those from California are tender even in parts of Britain, 

 and yet it is the same tree, seemingly, with some ele- 

 ment left out, and that spells hardiness. 



It is often the case that we find one specimen taken, 

 and the other left after a severe winter. A year ago 

 .some Diervillas (Wiegelias) were killed to the ground; 

 others were uninjured and flowered finely. All are 

 practically of one common origin from the same set of 

 Chinese species much mixed in gardens. An eminent 

 horticulturist was here last week and when speaking of 

 things that will live here and stand the winter, he asked 

 "Do the Diervillas live here?" and it may be taken for 

 granted that where they do not thrive, the list of avail- 

 able shrubs is cut in twain. Sometime since, another 

 wise man from Philadelphia visited here, and he was 

 asked to name off-hand ten shrubs of distinct genera, all 

 to be as good as Spiraea Van Houttei, and, if memory 

 serves, the task was not completed — he liad no book with 

 him. There was a distinct pause when the fingers on 

 one hand were counted off. W. C. Egan of Highland 

 Park makes the broad statement that we have no broad- 

 leaved evergreens that will thrive here, and he is right, 

 for Mahonia aquifolia but ekes out an existence. 



Much has been done in the past to render plants 

 liardier by obtaining seeds from the northern limit, 

 planting these and selecting those that survive for prop- 

 agation. This is of necessity a slow process with trees, 

 for the survivors take a long time to bear seeds in their 

 turn. 



Grafting with a view to hardiness often accentuates 

 tenderness unless a hardier stock is available. Jackson 

 Dawson told me years ago that the beautiful flowering 

 crabs should be grafted on the Siberian crab stock. I 

 found they would grow well on the common wild apple 

 seedlings, and in New England had Malus Arnoldiana 

 12 feet in diameter on a wild apple stock. Two years 

 ago we grafted 500 of the choicest obtainable flowering 

 crabs on seedling apple stock, over 20 varieties, and dur- 

 ing the winter of 1911-13 the whole of them died from 

 winterkilling at the roots; the tops were alive in the 



spring, but the roots dead. It might be added as a post- 

 script that Siberian crab seedlings were not obtainable 

 at the time fronf any source, and the apple stocks were 

 liought in far Minnesota. We have now 500 Siberian 

 crab seedlings on hand, and hope the end is not yet, but 

 it was necessary to get out, find the place where the 

 parent tree was growing, 1000 miles away, beg the seeds 

 and raise the same. 



A few weeks ago, a specimen of what is known there 

 MS Glyptostrobus sinensis pendula, was seen in a cem- 

 etery in I_;exington, Kentucky. It is not a Glyptostrobus 

 and is not Chinese, but a weeping form of our southern 

 cypress — ^Taxodium distichum, propagated or increased 

 only by grafting, not found in any American lists but is 

 listed in Europe. The type can be seen thriving as far 

 north as Lake Geneva, Wisconsin, but the weeping form, 

 naturally rare, is probably of southern origin, and Lex- 

 ington may be its northern limit. 



The English walnut, so called, was naturalized on 

 Long Island, N. Y., by the late Charles A. Dana. It 

 fruited freely, and I once gathered seeds there while vis- 

 iting William Falconer. These were raised and planted 

 ■^00 miles north, but the trees, though covered and pro- 

 tected well the first winters, always killed to the ground. 



A method of increasing hardiness is being practiced by 

 many of the Experiment Stations in the Northwest with 

 a view to getting fruit trees to stand the climate there. 

 The hardy Russian apples and other fruit trees are being 

 crossed with our own best kinds, and this must bring 

 good results. It is now proven by a very careful series 

 of experiments made in France, that two really good 

 varieties of apples crossed, produce in every seedling an 

 apple as good as the parents. Previous to this we be- 

 lieved eveiy good apple was an accident, at least as much 

 so as the Baldwin. 



It has been demonstrated time and again that one 

 severe winter-killing will make ligneous plants tender 

 for a period afterwards. The cutting down to the 

 ground induces strong soft shoots that are an easy prey 

 the next winter, and another factor is a long drouth dur- 

 ing the growing period in summer. In our soil, after 

 a drouth, most trees and shrubs start a secondary period 

 of vigorous growth that goes into the winter poorly 

 ripened and susceptible to injury. 



An old "Axiom" is, plant all doubtful subjects in 

 poor soil, and in this there is wisdom in that the growth 

 made is sure to be well matured. A south exposure 

 often brings the same results, especially if the soil is 

 well drained by having a gravel sub-soil. With us there 

 is no choice — nothing but an unmitigated clay without 

 a single redeeming vice — and the problem of extending 

 the planting list is eternal in its importance. A clay 

 soil can be rich in food for certain growths, as witness 

 the wonderful native oaks and other hardwoods here, 

 but when it comes to the decorative part of the gardener, 

 and where 100 car-loads of rhododendrons could be used, 

 except for the iron, lime, magnesia and a few other ele- 

 ments found in the water that leaches out of the soil, it is 

 not at all a question of hardiness, for Rhododendron 

 maximum is found far north of here growing in profu- 

 sion, likewise the trailing arbutus, and other ericaceous 

 plants, but with us a huckleberry would not live. This, 

 however, is a part of another story,- — The chemistry of 

 soils. 



Lal-e Forest, Illinois. 



