July 3, 1909 



HORTICULTURE 



Rhododendron indicum; Syn, 

 Azalea indica 



Enormous mmibers of this beautiful greenhouse flow- 

 ering shrub are bought every fall for forcing purposes, 

 and a gi-eat many find their way the following spring 

 to the rubbish pile simply because their culture is not 

 understood by the purchaser. This state of affairs can 

 easily be remedied if the following suggestions are car- 

 ried out fully, and perhajjs someone will be convinced of 

 the folly of discarding valuable plants, and of spending 

 money needlessly upon new stock. 



After the plants have flowered all dead blossoms and 

 seed pods should be removed, taking care not to injure 

 any new shoots which may he ajipearing, as these will 

 furnish the flower buds for the coming season. If neces- 

 sary, the plants should 'then be repotted, four-fifths of 

 fibrous peat and one-fifth of sand being a good potting 

 compost. Firm potting is essential. 



After potting, the plants should be placed in a green- 

 house with a temperature ranging between 60 and 70 

 degrees F. They should be syringed three or four times 

 a day to aid in the production of new wood and to pre- 

 vent the attacks of red spider, thrips, etc., to which the 

 plants are susceptible. By this treatment a nice head of 

 growth will Ije produced, and it is not necessary to 

 prune away an}' wood, except to shape the plants. They 

 can either be trained in a pyramidal or bush form. In 

 . the f 0! mer case, bamboo canes will be essential ; these 

 must be driven into the soil and a leading shoot selected 

 and trained thereto. 



About the middle or end of May the plants should be 

 removed to a cold frame and allowed to remain until 

 thoroughly hardened off, or, if no cold frame is avail- 

 able, they should be jDlaced in a sheltered place and cov- 

 ered at night in case of frost. After all danger of frost 

 is past, the pots should be plunged to the rims in coal 

 ashes in a position sheltered from strong winds, but to 

 which a fair amount of sunshine has access. This pro- 

 cedure will not only provide an anchorage for the plants 

 but will also prevent the soil moisture from escaping too 

 rapidly, thus saving extra labor in watering. 



Although the Rhododendron tribe will stand more 

 •water at the roots than most hard-wooded ericaceous 

 plants, care must be taken in this respect. Xever allow 

 the soil to become sodden, as this results in the death of 

 the young fibrous roots: on the other hanrl, a too dry 

 condition must be avoided. A good plan is to tap the 

 pots, and the answering ring will indicate approximate- 

 ly the amount of moisture present in the soil. If a dull 

 sound is heard the plants will not require water; if a 

 sharp ring, the reverse. Syringing sliould be practised 

 at least twice daily in drv weather. This will encourage 

 a nice clean growth until the flower buds begin to form. 



Toward the fall of the year syringing should be dis- 

 continued, and previous to the appearance of frost the 

 plants should be removed to a cool greenhouse, thence 

 placed in heat as required for forcing. Excessive heat is 

 not conducive to the successful forcing of any hard- 

 wooded plant, therefore . a temperature of from 50 to 

 60 degrees F. is high enough to start, and a temperature 

 of 7.5 ought to be regarded strictly as the maximum. 



Rhododendron indicum, as imported, usually pos- 

 sesses a fine root system, which is due to the peaty soil 

 in which it has been grown. As soon as it is in the 



liands of florists it is either potted in peat, or, in the 

 greater number of cases, in loam. If in the latter, it 

 will be observed that very few roots are formed, thus 

 proving that loam is not" at all desirable as a rooting 

 medium, and when used alone is certainly not conducive 

 to the production of a healthy root system. 



Our failures and those of others teach us better les- 

 sons than our successes, and we must discriminate be- 

 tween the right and the wrong methods in order to be 

 successful cultivators of any kind of plants. 



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Notes from the Arnold Arboretum 



A handsome species and very distinct from all other 

 commonly cultivated Clematis is the new Clematis erio- 

 poda (C. tangutica) from North Tibet with large yellow 

 nodding flowers. It is a woody climber growing about 

 ten feet high and having finely divided foliage and 

 bright yellow bell-shaped flowers about two inches long, 

 in shape resembling a half open yellow Tulip with 

 pointed petals; the flowers, however, are not borne up- 

 right, but nodding at the end of long and slender stalks 

 and are in shape and color very unlike any other Cle- 

 matis. The flowers appear successively during June 

 and July and are followed by very ornamental heads of 

 fruits with long feathery tails which persist on the 

 plant until autumn. Clematis eriopoda has proved per- 

 fectly liardy at the Arboretum and is to be recommended 

 as well for its attractive 'flowers as for its ornamental 

 feathery fruits. 



Another handsome and interesting vine and quite new 

 to cultivation is Periploca sepium introduced into the 

 Arnold Arboretum by Mr. J. G. Jack of the Arnold Ar- 

 boretum who collected seeds three years ago in northern 

 China. It is closely related to the Mediterranean P. 

 graeca which is in cultivation since a long time, but 

 little planted in this country; it is not perfectly hardy 

 in this latitude, while P. sepium appears to be quite 

 hardy, as is to be expected from plants native to north- 

 ern China. The Chinese species does not seem to be 

 such a vigorous grower as P. graeca which reaches a 

 height of about forty feet; it is smaller in every part. 

 Its dark green lustrous leaves are about two to three 

 inches long and narrowly lanceolate in outline: tlie flow- 

 ers appear in June and July "on slender stalks in few- 

 flowered clusters in the axils of the leaves : they are dark 

 purple when they open, changing later to greenish or 

 greenish purple, almost globular in shape and one-third 

 of an inch in diameter : this peculiar shape is caused by 

 the recurved petals which bear besides five thread-like 

 curved appendages arranged around tlie short stamens. 

 The flowers are not fragrant as are those of P. graeca. 

 The light green slender pods about three inches in length 

 and disposed in pairs are also attractive. The chief or- 

 namental vahie of this vine lies in the dark green lus- 

 trous foliaarc which remains unchanfred wntil late in 

 fall. 



