HYBRIDS 



HYDRANGEA 



1619 



The literature of hybridization is extensive but scat- 

 tered. The possibilities of hybridization as a factor in 

 plant-breeding are presented in many aspects in the 

 "Hybrid Conference Report" of the Royal Horticul- 

 tural Society, London, 1900. There are special books 

 devoted to orchid hybrids (see Orchids). See an excel- 

 lent paper by Swingle and Webber, "Yearbook of the 

 United States Department of Agricultm'c, " 1897; 

 papers in "American Gardening," 1899, pp. 397, 413, 

 431; Bailey & Gilbert's "Plant-Breeding;" De Uries' 

 "Plant-Breeding." L H. B. 



HYDRANGEA (Greek, hydor, water, and aggcion, 

 vessel; alluding to the cup-shaped fruit). Saxifraga- 

 cese. Ornamental woody plants, grow^l chiefly for their 

 showy white, pink or blue flowers. 



Deciduous shrubs: Ivs. opposite, without stipules, 

 petioled, serrate, sometimes entire, rarely lobed: fls. 

 perfect, in terminal panicles or corymbs, often with 

 sterile marginal fls.; calyx-lobes and petals 4-5; sta- 

 mens usually 10; ovary inferior or half-inferior; styles 

 2-5, short: caps. 2-5-cellcd, dehiscent at the base of 

 the styles, with many minute seeds. — About 35 spe- 

 cies in N. and S. Amer., Himalaj'as and Cent, and E. 

 Asia, of which more than 20 occur in China; for a key 

 to the Chinese species, see Rehder, Sj-nopsis of the 

 Chinese Hydrangeas (in Sargent, Plantae Wilsoniana 

 1:34-41). 



The hydrangeas are highly ornamental mostly low 

 shrubs, rarely vines climbing by rootlets, with medium- 

 sized or rather large leaves and .smaU white, bluish or 

 pinkish flowers in corymbs or panicles, bearing usually 

 marginal sterile flowers, with enlarged showy sepals, 

 or in some varieties all the flowers are sterile and 

 enlarged. H. paniculata is the hardiest of all, but H. 

 arborescens, H. radiata, H. xanlhoneura and H. Brii- 

 schneideri are also almost hardy North, while H. 

 guercifolia and H. pctiolaris are hardy as far north as 

 RIassachusetts, and H. involucrata, H. opuloides, H. 

 Sargcntiana, H. hcteromalla and H. Davidii, are still 

 more tender, and cannot be grown outdoors North. 



They grow best in a rich, porous and somewhat 

 moist soil and thrive well in partly shaded positions, 

 but flower more freely in full sun if they only have 

 sufficient moisture. All hydrangeas are well adapted 

 for borders of shrubberies, and H. paniculata and H. 

 opuloides, especially the varieties with sterile flowers, 

 are very showy as single specimens on the lawn. In 

 warmer climates the latter is .sometimes used for orna- 

 mental hedges (see G.C. III. 24:337, 456); but it is not 

 hardy in the North. These and also most of the other 

 species should be pruned in fall or early spring, and 

 the branches of the previous year cut back to one to 

 three pairs of buds, according to the growth of the 

 branches and the desired size of the panicles; if only 

 slightly pruned, the panicles will be many but small. 

 Sometimes they are cut back every year almost to the 

 ground and produce then enormous panicles, which, 

 however, usually need artificial support and lack the 

 gracefulness of less severely pruned plants. H. panicu- 

 lata var. grandiflora can be grown into a small standard 

 tree; for this purpose vigorous young plants should be 

 selected and planted in rich soil, and cut down to the 

 base. The strongest shoot of each plant wall attain by 

 fall the height of 4 to 6 feet, if freely manured and 

 watered during the summer; in autumn, all the weaker 

 branches are cut off, and in colder climates the plants 

 should be hfted and stored in a frost-proof pit or cellar, 

 since the wood is usually not sufficiently ripened to 

 withstand severe frost. In the following year the toj) of 

 the stem is allowed to branch. The weaker basal shoots 

 may be pegged down to make new plants. Strong- 

 growing varieties of H. opuloides may be treated in 

 the same way if standard plants are desired. 



The method of winter prot<'cti(m of hardy hydrangeas 

 adopted around Newport, Rhode Island (and possibly 



other places) may be worthy of mention. In the case 

 of individual specimens, after the leaves have dropped 

 in the fall, the branches are tied together and the 

 plant covered with a box having open ends. The box 

 is then filled with earth. When the plants are growing 

 together in a bed or border, they may be treated in a 

 similar way by placing boards along the side of the bed, 

 to assist in retaining the earth that is used as a covering 

 material. If, after the branches are tied, they are bent 

 over somewhat, a saving of labor is effected by reason 

 of a smaller quantity of earth being sufficient to .cover 

 them. (Montague Free.) 



H. opuloides, which cannot withstand much more 

 than 10° of frost, is in the North much grown as a pot- 

 plant, especially the more show}' varieties with large 

 heads of sterile flowers, and is extensively used for out- 

 4oor decoration during the summer. Late in fall, when 

 the leaves have fallen after frost, the plants are moved 

 to a frost-proof cellar and kept rather dry until spring, 

 when they are repotted in new soil and the growth of 

 last year cut back to one or 

 two pairs of buds. As a suit- 

 able soil may be recom- 

 mended a mixture of loam, 

 leaf-mold and sand, with 

 ground bone, dried cow-ma- 

 nure or some other kind of 

 manure added. During the 

 summer a hberal supply of 

 water should be given, also 

 occasionally apphcations of 

 liquid manure, until the flow- 

 ers have developed. They 

 may also be planted in the 

 open ground during the sum- 

 mer, lifted late in fall with a 

 large ball of earth, stored 

 over winter in a coldframe or 

 pit and planted out again in 

 Bpring; this will not injure in 

 any way the profusion of 

 flowers. In certain kinds of 

 soil the pink hortensias show 

 a tendency to turn blue, and 

 perhaps this can be caused 

 by adding iron fiUngs or 

 alum to the soil. H. opu- 

 loides is also a valuable plant 

 for forcing, and is much grown 

 for Easter, especially the 

 var. otaksa, on account of its dwarfer habit. Hand- 

 some pot-plants can be grown in one year from 

 cuttings. In February or March cuttings are in- 

 serted in the propagating-house with sUght bottom 

 heat, and planted in small pots as soon as they are 

 rooted. During the summer they may be easily grown 

 in pots and plunged outdoors in coal-ashes or in any 

 kind of porous soil, transplanted several times, and 

 freely watered and occasionally manured; or they may 

 be planted out in rich soil, exposed to the full sun, 

 where water should be liberally given and now and then 

 an apphcation of liquid manure. Last of September 

 they should be repotted in 8-inch pots, kept shady 

 some days until established, and afterward exposed 

 to the sun. After the first frosts they may be brought 

 into a cool greenhouse. If intended to have them in 

 flower for Easter, they should be transferred not later 

 than the fore part of January into a warmer house, 

 with a temperature gradually rising from 50° to 00°; 

 the plants should be freely watered, and about once a 

 week an application of liquid manure given until the 

 flower-buds are developed. The flowers should be 

 almost fully developed some time before they are 

 desired, that they may be hardened off in a cooler 

 house, since overforced plants are likely to collapse if 

 exposed to sudden changes of temperature. After 



lii 



1929. Summer cutting of 

 Hydrangea paniculata. 



