IRISH GARDENING 



VOLUME XVI 



No. 184 



Editor— J- W. Besant 



A MONTHLY JOURNAL DEVOTED TO THE 



ADVANCEMENT OF HORTICULTURE AND 



ARBORICULTURE IN IRELAND 



JUNE 

 1921 



Populus Generosa* 



By Prof. A, Henry. 



LIBRARY 



NEW YOKK 

 BOTANICAL 



OST of the vigorous poplars grown 

 for timber in Euroi^e are hybrid 

 trees of accidental origin, the re- 

 sult of seed produced by the 

 fertilization of one species by the 

 stray pollen of another species 

 wafted by the wind. An account of these, with 

 illustrations, appeared in this Journal, April, IMS, 

 p. 49. 



Populus gencrosa differs in being an artificial 

 hybrid, produced at Kew in -March, 1912, when the 

 pistillate flowers of a black poplar, Populus angu- 

 lata, were dusted with the pollen of a Balsam 

 poplar, Populus trichocarpa. From the few seeds, 

 Avhich ripened towards the end of June and were 

 sown immediately, four seedlings were raised at 

 Cambridge, which attained about two inches in 

 height by the end of October, 1912. Starting next 

 season as tiny plants in good soil at Glasnevin, they 

 grew with amazing vigour and by the end of 1914 

 had attained 7^ to 10 feet in height. (See Journal 

 Dcpt. Agric, Ireland, October, 1914, page 14, figs. 6 

 and 7.) The finest of the four original trees was 

 planted out at Avondale and promised to become a 

 great size; but it was mysteriously cut down last 

 winter. Another, sent to Mr. Hilher, Nurseryman, 

 Winchester, who propagated extensively froixi it, is 

 now planted out at Woburn. Another is in a private 

 garden at Eanelagh. The 

 growing in the Glasnevin 

 measures 27 feet in height, j 

 five feet above the ground, 

 v.liich produced flowers, few in number, for the 

 first time in the spring of 1919'. It flowered' again 

 ia April of the present year, the abundant catkins 

 towards the top of the tree making a fine show, as 

 may be judged from the photograph here repro- 

 duced, of a part of one of the flowering branches. 



The cross between Populus angulata and Populus 

 trichocarpa was repeated at K<'W in April, 1914; and 

 from the seeds which ripened in June of that year 

 some trees of Populus gencrosa (secuncla) were 

 raised, and three of these are now making remark- 

 al)le growth in Kew Gardens. Two planted out in 

 the Poplar Collection, Nos. l-Vt and 1.j7, are alike in 

 , measurements, with a height last March of 29 feet 



fourth, now figured, is 



Botanic Gardens and 



md 13 inches in girth at 



This is a female tree, 



Sj and a girth of I9 inches. 

 T> practically six years' growth 

 "' lawn near the Palm House i 

 ^ Tree No. 157 produced this 

 vj kins, which fell off on 30th 

 The botanical characters n 



This is the result of 

 . The tliird tree on the 

 < somewhat less in size, 

 spring a few male cat- 

 uid 31st March. 

 f Populus gencrosa were 



given, as I'&gards the twigs and foliage, in the. 

 original description of the hybrid, which was pub- 

 lished in Gardeners' Chronicle, 17th October, 1914, 

 p. 257, figs. 102, 103, and need not be repeated here. 

 1 may now add a few technical notes on the flowers : 

 Catkins of both sexes pendulous with numerous 

 flowers on a glabrous axis; pedicels short, glabrous; 

 scales fugacious, fan-shaped, with margin variously 

 lobed and divided into long irregular slender fila- 

 mentous segments. ]\Iale catkins 4 to 5 inches long; 

 anthers oO to GO, reddish, with long white filaments; 

 disc glabrous, with a few indistinct teeth on the 

 margin. Female catkins, 5 to 6 inches long; disc a 

 shallow glabrous cup, with crenate margin; ovary 

 sessile, glabrous, usually with three placentae bear- 

 ing numerous ovules; stigmas usually three, broad 

 and variously lobed. Earely only two placentae and 

 two stigmas are present. The flowers differ from 

 P. angulata in the shape of the scale, which has a 

 dentate margin in that species. They differ more, 

 however, from P. trichocarpa, in which the ovary 

 and the axis of the catkin are tomentose. 



Populus gencrosa is w'orth growing for ornament, 

 as it bears vei-y large leaves, sometimes 9 to 10 

 inches across, which turn a brilliant yellow in 

 autumn. It grows fast in youth, as the measure- 

 ments already given indicate ; and at Oxford cuttings 

 sent from Dublin surpassed in vigour in the second 

 year the well-known hybrids Populus regencrata, 

 Populus Eugenci, and Populus rohusta. (See 

 Quarterly Journal of Forestry, April, 1918, page 135.) 

 Whether it will eontiuue to grow at the same rate 

 and be of use for producing timber quickly, is a 

 matter of some doubt. 



In the Alpine House, Glasnevin. 



Primula fasciculata. — This new species from China, 

 seed of which was received from Edinburgh Botanic 

 Gardens, has sorrel-like leaves of a bright green 

 eoloiu'. The flowers are rose jiink Avith a yellow eye; 

 those at present open are all sthnnn-eyed. The 

 plant stands 3^ inches high, and if it proves hardy 

 will bo a delightful addition to rock gai'dens. 



Primula rcdolcns, also from China; the leaves and 

 liabit are somewhat like P. Forrestii, the same rough 

 netting on the leaves. The stems are moderate, 

 to 8 inches ; three to four flowers in a head : the 

 coloiu- palest pink with a pale orange eye. They 

 are like P. obconica. in shape. The plant is well 

 named; its scent is very sweet, like cowslips. 



W. P. M. 



