GROWING PLANTS WITHOUT SOIL FOR EXPERIMENTAL USE 



15 



supplied continuously, or they may be directly 

 seeded into vermiculite-filled screen frames (fig. 2) 

 and moistened with one-third strength solution 

 to obtain a dense stand. 



Bean 'Black Valentine,' Broadbean, Limabean, 

 and Pintobean. — These species have a wide 

 nutritional tolerance. The first symptom of 

 deficiency is a reduction in leaf area of newly 

 expanding leaves that may be readily corrected 

 before any leaf injury becomes apparent. Pollina- 

 tion of broadbean flowers is best done by hand 

 or by using an oscillating fan near the plants for a 

 few hours each day. The relative humidity should 

 be kept low for maturing limabeans to prevent 

 seed from sprouting while still in the pod. 



Beet and Sugarbeet. — If these species are to be 

 raised in vermiculite without transplanting, they 

 may be supplied with one-half strength solution 

 at time of seeding. 



Bermudagrass and Bluegrass. — Vegetative prop- 

 agules of bermudagrass may be obtained from 

 sections of runners. Freshly harvested bluegrass 

 seeds are often dormant. Good germination of 

 2- to 4-year-old seed can be obtained by moisten- 

 ing with nutrient solution under high humidity. 

 Once germinated, the seedlings should be grown 

 under low humidity to prevent mildew infection. 

 Bluegrass may be vegetatively propagated by 

 subdividing the crowns. 



Buckwheat. — This species requires hand or 

 insect pollination to insure seed set. 



Cabbage, Mustard, and Wild Mustard. — Some 

 stem injury to cabbage may occur if young 

 plants are not well supported in liquid cultures 

 or if nutrient salts are allowed to accumulate 

 on stems. Mustard grows better in vermiculite 

 than in liquid culture. Wild mustard has low 

 nutrient requirements and leaf burn may occur 

 if solutions more concentrated than one-third 

 strength are used. Mature plants are large enough 

 to tip solution culture jars if they are not well 

 supported. 



Carrot. — Roots of this species are abnormally 

 branched and short when grown in solution 

 culture. 



Corn. — This species is sensitive to nutritional 

 changes during the first 4 to 6 weeks and requires 

 a plentiful iron supply at all times. If grown in 

 solution culture, best results are obtained when 

 the solution pH is maintained near 7. Plants will 

 be severely stunted if grown in 500-ml. containers. 



Two-liter solution containers or 18-cm. pots are 

 recommended if corn is to be grown to maturity. 



Cotton. — Seed should be moistened with one- 

 half strength solution if started in vermiculite or 

 with one-third strength solution or 1 X 10 -4 M 

 calcium chloride if started in a paper roll for best 

 seedling root development. Leaves may become 

 mottled if plants are grown under high humidity. 



Cucumber, Melon, and Squash. — Vines of these 

 plants will occupy a great deal of space unless 

 staked up, and pruning is recommended to prevent 

 excessive branching. When foliage is removed by 

 pruning, the nutrient requirements are correspond- 

 ingly reduced. When these plants are grown in- 

 doors, hand pollinating is required to obtain 

 good fruit set, and thinning to control fruit size 

 may be required. The squash variety 'Golden 

 Nugget' is determinate and suitable for growing 

 in a restricted space. It remains bushy with the 

 fruits at the base of the plant. These species are 

 all susceptible to mildew if grown under high 

 humidity. 



Endive. — This species develops a very extensive 

 root system as compared with other species when 

 grown hydroponically. 



Flax and Red Clover. — Stem cuttings rooted in 

 aerated water may also be used to propagate 

 these species. After rooting, the cuttings are 

 supplied with one-third strength solution. When 

 grown in vermiculite, flax should be given small 

 amounts of nutrient solution at any given time. 

 Excess moisture will cause yellowing of lower 

 leaves and nutrient stress will cause yellowing of 

 upper leaves. Red clover can be grown well in 

 screened frames (fig. 2) when one-fourth strength 

 solution is used continuously. 



Johnsongrass. — This species is easily grown 

 from rhizome sections. Plant development is 

 normal in vermiculite, but poor rhizome develop- 

 ment is obtained when grown in liquid culture. 



Millet, Sorghum, and Sudangrass. — Rust-colored 

 blotches will occur on leaves of these species 

 under high humidity. 



Okra. — This species has low nutritional re- 

 quirements, and older leaves will become senescent 

 if the nutrient solution is allowed to become too 

 concentrated. 



Peanut. — This species grows well to maturity in 

 vermiculite. Large containers should be used to 

 permit normal fruit development. Young plants 



