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Bulbs

Bulbs. Defn: specialized underground structures with a basal plate bearing a growing point, enclosed by thick, fleshy scales Propagation methods offsets bulblet separation from flowering stems stem cuttings scaling basal cuttage leaf and bulb cuttings micropropagation.

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Bulbs

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  1. Bulbs • Defn: specialized underground structures with a basal plate bearing a growing point, enclosed by thick, fleshy scales • Propagation methods • offsets • bulblet separation from flowering stems • stem cuttings • scaling • basal cuttage • leaf and bulb cuttings • micropropagation

  2. Propagation of bulbs by offsets • Used extensively for tulips and daffodils • tulips - features: • bulbs are dug in the summer • offsets are separated, graded for size • stored, replanted the same fall • offsets usu. require 2-3 growing seasons to achieve flowering size

  3. Photo showing various shapes, sizes and colors of tulip flowers (Rix 1981)

  4. Fig. 15-1. Structure of tulip, a tunicate bulb, with parts labelled.

  5. Developing offset

  6. Offset propagation of Narcissus (daffodils) • flowering bulb continues growth from the center (as opposed to tulips) each year • propagation method is similar(to tulips), by separation of the offset or “split” • harvested bulbs are graded: 1st yr (“round” or “single-nose”, 2nd yr (“double nose”), and 3rd yr (“mother bulbs”)

  7. Photo showing various flower colors of daffodil (Rix 1981)

  8. Well-developed offsets Double-nosed bulb

  9. Amaryllis (Hippeastrum)

  10. Bulblet separation from flowering stems • useful for propagation of Easter lilies • method: • underground bulblets pulled from flowering stems • planted in late fall (Pacific Northwest) • dug the following Sept., graded and replanted • 2 yrs to commercial bulbs

  11. Fig. 15-5. The flowering stem of Easter lily.

  12. Main flowering bulb Offsets attached to the stem of the flower stalk

  13. Stem cuttings of bulbs • used for Easter lilies • cuttings are made from flowering stems (after flowering), then stuck in moist medium • bulblets form in leaf axils • some lilies also form bulbils in leaf axils of the flowering stem

  14. Bulb scaling • useful for a wide variety of lily species • scales are separated from the bulb (individual scales separate readily from this nontunicate bulb) • adventitious bulblets form at the base of each scale • bulblets are usu. vernalized for sev. weeks, then planted • scaling can also be done by tissue culture for multiplying virus-indexed stock

  15. Fig. 15-4. The structure of the Easter lily bulb, with parts labelled.

  16. Basal cuttage • useful for hyacinths • basal plate is removed (“scooped”) or “scored” (to remove the growing point • adventitious bulblets develop from the base of exposed bulb scales

  17. Photo of the hyacinth flowering shoot (Harrison 1967)

  18. Figure of a hyacinth bulb with bulblets forming after bulb scoring (Clark and Toogood 1990)

  19. Photos showing bulb scoring and scooping (Free 1957)

  20. Leaf cuttings of bulb species • useful for grape hyacinths (Muscari botryoides), blood lily (Haemanthus coccineus), common hyacinths (Hyacinthus orientalis) • similar to leaf cuttings of other herbaceous plants, except a bulblet forms at the base of the leaf cutting

  21. Bulb cuttings • useful for Narcissus, Hippeastrum (Amaryllis) • called “bulb chipping” or “fractional scale-stem cuttage” • mature bulb is cut into 8-10 vertical sections, then further divided by cutting between every 3rd or 4th concentric scale, through the basal plate • “twin scaling” is a variation on this method

  22. Fig. 15-12. Twin-scaling of Narcissus.

  23. Micropropagation of bulb species • useful for iris (bulbous), hyacinth, and (increasingly) Narcissus, Hippeastrum, and Lilium (e.g., 12 million annually in the Netherlands) • increase is by shoot multiplication, bulblet induction on scales followed by bulblet division, or bulblet induction on flower scapes

  24. Photo showing micropropagation of bulbous iris (Zimmerman et al. 1986)

  25. Fig. 15-10. Micropropagation of bulbous iris and hyacinth.

  26. Propagation of corms • useful for gladiolus and freesia • corm: the swollen base of a stem axis, enclosed by dry, scale-like leaves • propagation methods • separation of offset corms • cormels (miniature corms between old and new corms) • corm division (retaining a bud with each section) • micropropagation (both glads and freesias)

  27. Fig. 15-13 and 15-14. Photo and diagrams of gladiolus corms, with parts labelled.

  28. Photo showing gladiolus micropropagation (Zimmerman et al. 1986)

  29. Recap • Bulb propagation • Offsets (tulip and daffodil) • Bulblet separation from flowering stems (Easter lily) • Stem cuttings (lily) • Scaling (lily) • Basal cuttage - scoring and scooping (hyacinth) • Leaf and bulb cuttings - e.g., bulb chipping, twin scaling (narcissus, amaryllis) • Micropropagation (iris, hyacinth, narcissus, amaryllis, lily)

  30. Recap - contin. • Corm propagation (gladiolus, freesia) • Separation of offset corms • Separation of cormels • Corm division • Micropropagation • And, from the text: What is the advantage of growing tulips for bulb production in the Pacific Northwest (of the U.S.)? What happens if the bulbs are dug too early or if warm weather causes early maturation?

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