GREENHOUSE 



GREENHOUSE 



1409 



of plants under glass is this: Each plant has its own 

 season of bloom. Every good gardener knows the 

 times and seasons of his plants as he knows his alphabet, 

 without knowing that he knows. Yet there are many 

 failures because of lack of this knowledge, particularly 

 among amateurs. The housewife is always asking how 

 to make her wax-plant bloom, without knowing that it 

 would bloom if she would let it alone in winter and let 

 it grow in spring and summer. What we try to accom- 

 plish by means of fertilizers, forcing and other special 

 practices may often be accomplished almost without 

 effort if we know the natural season of the plant. Nearly 

 all greenhouse plants are grown on this principle. We 

 give them conditions as nearly normal to them as pos- 

 sible. We endeavor to accommodate our conditions to 

 the plant, not our plant to the conditions. Some plants 

 may be forced to bloom in abnormal seasons, as roses, 

 carnations, lilies (see Forcing). But these forcing 

 plants are few compared with the whole number of 

 greenhouse species. The season of normal activity is 

 the key to the whole problem of growing plants under 

 glass; yet many a young man has served an apprentice- 

 ship, or has taken a course in an agricultural college, 

 without learning this principle. 



The second principle is like unto the first: Most plants 

 demand a particular season of inactivity or rest. It is 

 not rest in the sense of recuperation, but it is the habit 

 or nature of the plant. For ages, most plants have been 

 forced to cease their activities because of cold or dry. 

 These habits are so fixed that they must be recognized 

 when the plants are grown under glass. Some plants 

 have no such definite seasons, and will grow more or 

 less continuously, but these are the exceptions. Others 

 may rest at almost any time of the year; but most 

 plants have a definite season, and this season must be 

 learned. In general, experience is the only guide as to 

 whether a plant needs rest; but bulbs and tubers and 

 thick rhizomes always signify that the plant was 

 obliged, in its native haunts, to carry itself over an 

 unpropitious season, and that a rest is very necessary, 

 if not absolutely essential, under domestication. 

 Instinctively, we let bulbous plants rest. They usually 

 rest in our winter and bloom in our spring and summer, 

 but some of them of which some of the Cape bulbs, 

 as nerines, are examples rest in our summer and bloom 

 in autumn. 



The third principle from the plant side is this: The 

 greater part of the growth should be made before the 

 plant is expected to bloom. It is natural for a plant first 

 to grow: then it blooms and makes its fruit. In the 

 greater number of cases, these two great functions do 

 not proceed simultaneously, at least not to their full 

 degree. This principle is admirably illustrated in woody 

 plants. The gardener always impresses on the appren- 

 tice the necessity of securing "well-ripened wood" of 

 azaleas, camellias, and the like, if he would have good 

 flowers. That is, the plant should have completed one 

 cycle of its life before it begins another. From imma- 

 ture and sappy wood only poor bloom may be expected. 

 This is true to a degree even in herbaceous plants. 

 The vegetative stage or cycle may be made shorter or 

 longer by smaller or larger pots, but the stage of rapid 

 growth must be well passed before the best bloom is 

 wanted. Fertilizer applied then will go to the pro- 

 duction of flowers; but before that time it will make 

 largely for the production of leaf and wood. The 

 stronger and better the plant in its vegetative stage, 

 according to its size, the more satisfactory it should be 

 in its blooming stage. 



Closely like the last principle is the experience that 

 checking growth, so long as the plant remains healthy, in- 

 duces fruitfulness or floriferousness. If the gardener 

 continues to shift his plants into larger pots, he should 

 not expect the best results in bloom. He shifts from 

 pot to pot until the plant reaches the desired size; then 

 he allows the roots to be confined, and the plant is set 



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into bloom. Over-potting is a serious evil. When the 

 blooming habit is once begun, he may apply liquid 

 manure or other fertilizer if the plant needs it. The rose- 

 grower or the cucumber-grower wants a shallow bench, 

 that the plants may not run too much to vine. 



A carnation-grower writes that there is "little dif- 

 ference in the yearly average as to quality or quantity 

 of flowers, but plants grown on shallow benches come 

 into flower more quickly in the fall. Those grown in 

 solid beds produce an abundance of flowers later in 

 the season. The preference of commercial carnation- 

 growers is for raised benches so that there may be more 

 blooms early in the fall and at the Christmas holidays." 



The natural habitat of the plant is significant to the 

 cultivator; it gives a suggestion of the treatment under 

 which the plant will be likely to thrive. Unconsciously 

 the plant-grower strives to imitate what he conceives to 

 be the conditions, as to temperature, moisture and sun- 

 light, under which the species grows in the wild. 

 We have our tropical, temperate and cool houses. Yet, 

 it must be remembered that the mere geography of a 

 plant's native place does not always indicate what the 

 precise nature of that place is. The plant in question 

 may grow in some unusual site or exposure in its native 

 wilds. In a general way, we expect that a plant com- 

 ing from the Amazon needs a hothouse; but the details 

 of altitude, exposure, moisture and sunlight must be 

 learned by experience. Again, it is to be said that 

 plants do not always grow where they would, but 

 where they must. Many plants that inhabit swamps 

 thrive well on dry lands. 



Yet, the habitat and the zone give the hint: with 

 this beginning, the grower may work out the proper 

 treatment. Examples are many in which cultivators 

 have slavishly followed the suggestion given by a 

 plant's nativity, only to meet with partial failure. Be- 

 cause the dipladenia is Brazilian, it is usually supposed 

 that it needs a hothouse, but it gives best results in 

 a coolhouse. Persons often make a similar mistake in 

 growing the pepino warm, because it is Central and 

 South American. Ixia is commonly regarded in the 

 North as only a glasshouse subject because it is a Cape 

 bulb, yet it thrives in the open in parts of New England, 

 when well covered in winter. 



The best method of propagation is to be determined for 

 each species; but, as a rule, quicker results and stockier 

 plants are secured from cuttings than from seeds. Of 

 necessity, most greenhouse plants are grown from cut- 

 tings. In most cases, the best material for cuttings is 

 the nearly ripe wood. In woody plants, as camellias 

 and others, the cutting material often may be com- 

 pletely woody. In herbaceous plants, the proper mate- 

 rial is stems which have begun to harden. Now and then 

 better results are secured from seeds, even with peren- 

 nials, as in grevillea and Impatiens Sultani. 



Coming, now, to some of the principles that underlie 

 the proper management of the house, it may be said, 

 first of all, that the grower should attempt to imitate a 

 natural day. There should be the full complement of 

 continuous sunlight; there should be periodicity in 

 temperature. From the lowest temperature before 

 dawn, there should be a gradual rise to midday or later. 

 As a rule, the night temperature should be 10 to 15 F. 

 below the maximum day temperature in the shade. A 

 high night temperature makes the plants soft and tends 

 to bring them to maturity too early. It makes weak 

 stems and flabby flowers. The temperature should 

 change gradually : violent fluctuations are inimical, par- 

 ticularly to plants grown at a high temperature. 



In greenhouse cultivation, every plant is to receive in- 

 dividual care. In the field, the crop is the unit: there 

 we deal with plants in the aggregate. In the green- 

 house, each plant is to be saved and to receive special 

 care: upon this success depends. There should be no 

 vacant places on the greenhouse bench; room is too 



