THE EFFECT OF PLANTING DEPTH ON EMERGENCE AND DEVELOPMENT OF SOME GEOPHYTIC PLANTS
Plants chosen were: Anemone coronaria, Ranunculus asiaticus, Crocus sativus, Iris xiphium,. Allium cepa, Allium sativa, Aconitum napellus, Hyacinthus, Narcissus tazetta, and Ornithogalum arabicum. They were planted in late autumn, in sandy soil at two in Israel. The bulbs or corms were placed carefully at the bottom of drilled holes (9 cm in diameter) and covered with local soil to ground level. Data collected included: leaf emergence and flowering vs. days from planting, the number of shoots, leaves and flower stems. When plants entered dormancy, the bulbs and the corms were dug out carefully and their depths recorded, they were counted, afresh and oven dry weights were determinated.
The plants were classified into three groups, according to their ability to emerge from the different depths: (i) Plants emerging from depths of 0 to 30 cm: Anemone, Ranunculus, and Crocus; (ii) Plants emerging from 0 to 50–60 cm: Iris, Allium, Aconitum, and Hyacinthus; and (iii) Plants emerging from 0 to 90cm: Narcissus, and Ornithogalum. An increase in planting depth delayed emergence and reduced the percentage of emerging plants. The number of developing shoots, leaves, and flowering stems, the number of daughter bulbs or corms, and their fresh and dry weights, were negatively correlated with the planting depth. Most of the bulbs and corms were found at the end of the growing season at the original depth. Ranunculus and Aconitum when planted deep, formed new geophytic organs above the planting depths and close to the ground surface.