How to Force Rhododendrons 



By B. B. C. Felix, of Boskoop, Holland. 



Besides the beautiful effects that can be had with 

 the Rhododendron in landscape architecture, they are 

 ideal forcing plants, and their popularity stands pre- 

 eminent with the Azalea Indica. Their heavy, dark 

 green, leathery foliage is striking, to say nothing of 

 the great masses of varied colored flowers, which are 

 produced in large trusses on the end of every branch of 

 the plant. There is such a variety of color in the long 

 list of varieties that, with a judicious selection, it is 

 possible to make any desired color arrangement. The 

 colors are generally pure and show variegations from 

 pure white to clear violet, delicate pink and deep crim- 

 son. Between the numerous bouquets the green of 

 the foliage is well displayed and adds to the beauty 

 of the plant. 



Although I mentioned large trusses I am sorry to 

 say that the Rhododendron which is forced in the 

 spring does not always show them as large and well 

 colored as they should be and though it is not alto- 

 gether impossible that the plant is at fault, yet I ascribe 

 it to wrong treatment in forcing in the majority of 

 cases. It takes time and care to get a Rhododendron 

 into bloom and also a knowledge of the different va- 

 rieties, whether they are early, medium or late bloom- 

 ing. Ignorance of this invariably leads to failure. By 

 reason of the success we had with our Rhododendrons 

 at various exhibitions and especially at the great flower 

 show at Boskoop, we received a number of letters ask- 

 ing us how we managed to have so many varieties in 

 bloom at one time. There were early, medium and late 

 blooming varieties in the collection. 



I shall try to explain the most important rules for 

 forcing Rhododendrons, but it should be understood 

 that the forcer must use his own judgment a great deal. 

 He must understand the exact needs of the plants and 

 their requirements as to airing, watering and heating. 



When a Rhododendron is sent out it is fully prepared 

 for forcing. The peaty soil in Boskoop is the ideal soil 

 for this class of plants, especially for those destined to 

 forcing. It may be possible to grow Rhododendrons in 

 sandy soil and they may also be useftil for planting out- 

 doors, but for forcing nothing can rival those grown 

 in our peat and climate. Here they flourish and thrive 

 to perfection and make strong buds which will easily 

 respond to the applied heat. We take special care in 

 growing these plants, not only as to the size of the flowers, 

 but the color also depends on this to a large extent. 



After the cases have arrived from Holland they 

 should at once be unpacked. It is well to be prepared 

 for them when they are expected, so that they can be 

 properly taken care of. Generally they are more or less 

 dry at the roots and should be placed in a shallow tank 

 or other receptacle to moisten them. There they can 

 be left for half an hour or so. The canvas should be 

 taken oi? the rootballs, and the heads untied. It is best 

 to pot them immediately in not too large pots. Pot 

 them if possible with leafmould and do not ram the 

 soil too hard in the pots. Firm potting is all right but 

 there is no need to go to extremes. The bottom of the 

 pots should be covered with potsherds. If the balls are 

 too heavy shake off the superfluous soil but do not cut 

 the roots. Then look over the plant carefully that 

 there are not too many flowerbuds on them. Some 

 varieties make three or four buds on the same branch 

 and these should be taken off so that only one, the 

 strongest, is left. There may also be too many buds 

 on the plant, so that they are in each other's way. These 



superfluous buds should be broken out to allow those 

 that remain on the plant sufficient space to develop 

 properly. 



The pots can now be heeled into a cold frame. In 

 fine weather or a mild rain the lights must be taken off 

 and only in cold freezing weather should be put on. Do 

 not place them in the hothouse immediately. The ob- 

 ject is to get the roots to sprout. The better they are 

 rooted the better they will force. The plants should 

 be given a fair amount of room. If possible let each 

 plant stand clear of its neighbor, so that light and air 

 can pass freely between them. If placed too close they 

 drop their leaves. This will also be the case if the 

 frames are kept closed too long at a time and the plants 

 are deprived of fresh air. Light and air are the two im- 

 portant requirements for forcing Rhododendrons. They 

 should be safe from frost. Watering should be done 

 only when necessary. 



In the frame they should be left till early January, 

 when the}' may be taken into the greenhouse. A tem- 

 perature of 50 to 60 degrees F. can be given to start 

 with. After four or five weeks the roots begin to 

 sprout (make new roots) and from that time a higher 

 temperature, not exceeding 70 to 75 degrees F., can be 

 applied. 



In the first days the Rhododendrons are in the green- 

 house the leaves must be syringed with a thin spray 

 once a day, but after the temperature is raised, and es- 

 pecially on sunny days, spraying twice a day will be 

 necessary. Do not use the hose. Just a thin spray is 

 sufficient. The pots should be watered now and then. 

 By the middle of March the glass has to be shaded to 

 prevent the leaves being burned. Shading with canvas 

 or similar material is preferable to whitewashing. The 

 pots should also be watered abundantly. Especially 

 when the buds are expanding the pots can hardly be 

 kept too wet. It is advisable to always have a moist 

 atmosphere in the house. 



When Rhododendrons are taken into the greenhouse 

 early in January some of the earliest blooming varieties 

 can be had in bloom by the beginning of March. After 

 these the medium and late flowering varieties follow in 

 succession, so that about the middle of .April the latest 

 flowering varieties can be had in bloom. Spraying on 

 the open trusses should be avoided. 



If a number of varieties are wanted in bloom at a 

 fixed time, then the earlv flowering varieties must be 

 brought inside later than the medium, and these again 

 later than the late flowering varieties. 



When they are all inside four or five weeks some 

 buds will be seen advancing. These plants must be 

 taken out and placed cooler, till they are all advanced 

 alike. Then they can be forced into bloom by the same 

 temperature. 



Note that late varieties should never be forced early. 

 This costs a lot of heqt and the results are doubtful. It 

 is very essential to know if a variety is early, medium 

 or late. Ignorance leads to disappointment and is gen- 

 erally the cause that Rhododendrons do not force satis- 

 factorily. 



TREATMENT OF FROZEN PLANTS. 



It is one of the curious and none the less vexatious 

 ironies of gardening that the heating apparatus of 

 greenhouses or frames, if it ever does fail at all, will 

 do so just when the country is in the grin of frost, and 

 the gardener under those circumstances finds, when he 



