July. 31, 1915 



HORTICULTURE 



131 



ROSE GROWING UNDER GLASS 



^ ^ CONDUCTED BY 



Questions by our readers in line with any of the topics presented on this page jUl be oordlally ^/''^^^ ^Yct^TDRE.^ ''°*'^"^"* 

 by Mr. Ruzicka. Such communications should invariably be addressed to the office of HORlll-UL,iUKa. 



Care of Old Plants 



Old plants that have just been cut off and planted 

 again in the benches will require every possible care to 

 bring them to their first growth, after which they will 

 be easier to handle, although to make them pay they 

 must never be neglected for an instant. We find that 

 it pays to give these plants even less soil than we would 

 give young plants^ for if the weather in the fall and 

 winter should be very dark, less trouble will be experi- 

 enced with the drying out of the benches. It is well to 

 have plenty of well decayed manure in the soil as they 

 will taj^e more feed than young plants, and if not fed 

 enough will produce a great many short-stemmed flow- 

 ers, mostly Ko. 2's, and these are not very profitable to 

 the grower. Syringe twice daily right after they are 

 planted, being very careful to do the work quickly, so 

 as not to get too much water on the benches. To do 

 this right, the walks must be in good condition, so that 

 the man with the hose can walk right along watching 

 the plants and his work without having to look ahead 

 to see that he does not walk into a hole, or slip on the 

 slimy earth walks sometimes tolerated in greenhouses. 

 A coat of sand is the very best these walks could get, 

 with a little lime added to help kill the green. Ashes 

 we would not recommend where pipes touch the walk, 

 as these eat through the pipes in a very little time. 



When syringing the plants that have already broken 

 into leaf, see that they are wet enough, otherwise the 

 foliage will likely be burned, and that is bad for plants 

 that are just starting. As soon as there is enough 

 growth to hide the main stalks, stop syringing, and 

 syringe only as often as necessary to keep the plants 

 clean, choosing the forenoon of bright clear days. 

 Watering will also play an important part in starting 

 old plants, and if done verj' careful!}', the loss from 

 plants dying will be very small. 



Lime 



In the early planted houses, where the plants have 

 attained some size, it will be necessary' to use a little 

 lime every night when the plants are watered or syringed 



HYDRANGEAS AT ARNOLD ARBOR- 

 ETUM. 

 Hydrangea radiata. A form ol Uy- 

 drangea arborescens (var. (iratidi- 

 flora), with large globose heads of 

 sterile flowers, lias become imnirnsely 

 popular in this country since iis dis- 

 covery a few years ago in one of the 

 western states, and it can now lie seen 

 in many suburban gardens. A much 

 more beautiful American species, how- 

 ever, is Hiidran'jcn radiata, which is 

 now in flower in the Shrub Collection. 

 It is a native of mountain slopes In 

 North and South Carolina, and is a 

 round-topped shrub with largo leaves 

 very dark green above and silvery 

 white below, and broad heads of flow- 

 ers surrounded by a ring of white neu- 

 tral flowers. It is one of the hand- 

 somest of all the Hydrangeas which 



in the day time. Some nights are very cool and foggy, 

 and if no lime is used the plants will likely suffer under 

 the leaves from the moist air that stays around the bot- 

 tom, and will be more apt to get mildew or spot. It is 

 very good to use a little lime at night after a thunder 

 storm in the afternoon, especially if the rain beat in. 

 Use lime in old leaky houses when a shower comes up 

 in the afternoon. Growers will say it is not necessary 

 to use lime except for Beauties, but we like to use it 

 for all roses, as there is very little expense attached to 

 it, and the benefit is many times the small outlay. 



Liquid Manure 



It is still too early to use this on plants that are not 

 well rooted, but any houses that have been grown for 

 summer blooming should receive liberal doses. Do not 

 mix any strong chemicals into it, using only a good lot 

 of cow manure. If nitrate and other strong fertilizers 

 are added, the plants are bound to get a little soft, and 

 are likely to get a dose of mildew. If the liquid nianure 

 is not very strong, add a little bonemeal to it but 

 nothing else. 



Mulching 



Watch the early planted houses, and see that the 

 roots do not suffer by being exposed to the rays of the 

 sun. Beauties especially will be working well to the 

 surface now, and a protecting mulch of manure will do 

 wonders in giving the plants color and keeping them in 

 good growing condition. The roots that suffer most are 

 the young tender feeders that supply the plant with 

 food. These vnW appear right on the surface if the 

 plants are mulched, and growers should be careful not 

 to scratch the benches over deeply, as this would de- 

 stroy all the tender roots and thus set the plants back. 

 \Protect all the roots for they are very important to the 

 growing plant. If the plants have poor roots, the feed, 

 water, etc., that is given them will largely be wasted, 

 as they will have no way to take it up. Get the soil 

 full of roots and keep these alive by careful watering 

 and feeding, taking care to give the necessary mulching 

 when it is required. __^ 



the ray flowers. The handsomest and 

 earliest of these was raised from seeds 

 collected by Professor Sargent in Hok- 

 kaido where it grows into a small 

 tree sometimes twenty or thirty feet 

 tall. — Arnold Arboretum Bulletin. 



are perfectly hardy in this climate, 

 and although once a popular garden 

 plant it is now rarely found in col- 

 lections. 



Hydrangea paniculata. More con- 

 spicuous now in the collection is the 

 early-flowering form of Hydrangea 

 paniculata (var. praerox). The most 

 generally planted form of Hydrangea 

 paniculata is that in which all the 

 flowers are sterile, known as Hy(/ro»- 

 gca paniculata grandiUora. This plant 

 produces large clusters of white flow- 

 ers which turn rose color in fadin,?, 

 and will not be in bloom for several 

 weeks. The variety praerox, which is 

 one of the forms of the wild plant, has 

 ray flowers surrounding the clusters 

 of sterile flowers. There are two or 

 three forms of the variety praecox in 

 the collection differing in the size of 

 the flower-clusters and in the size of 



During the next month several In- 

 tresting plants will flower in the Ar- 

 nold Arboretum. Among trees may 

 be mentioned the Chinese Koclrew- 

 trria paniculata. the .\mcrican and 

 .\siatic forms of Aralia spinosa, the 

 .lapanese Acanthopanax ricinifolium 

 and Sophora japonica; and among 

 shrubs the Pepper-bush of the eastern 

 Inlted States (CIcthra ainifolia), 

 which has been largely used in the 

 roadside plantations, and Panax ses- 

 siliflorus from eastern Siberia. 



The Arboretum Bulletins will now 

 be discontinued until autumn. 



