Herbaceous Bulbs – Summary

Bulbs are specified with reference to the following criteria:

  • Circumference
  • Condition
  • Other Factors

General requirements regarding CONDITION are given in the Herbaceous Bulbs section. With regard to CIRCUMFERENCE, bulbs, corms and tubers are very variable and the following table (taken from BS 3936 Part 9) gives information for the main types. urther information, for other species, hybrids or varieties can be obtained from specialists.

Species Min.
circ’ference
Grades
Allium moly 3 3/4; 4/5; 6/+
Anemone blanda 4 4/5; 5/6; 6/7; 7/8; 8/+
Chionodoxa 4 4/5; 5/6; 6/+
Colchicum spp. 13 13/14; 14/15; 15/+
Cyclamen hederifolium + similar spp. 6 6/8; 8/10; 10/12; 12/+
Eranthis 3 3.5/4; 4/5; 5/+
Fritillaria imperialis 18 18/20; 20/22; 22/+
Fritillaria meleagris 5 4/5; 5/6; 6/+
Galanthus nivalis 4 4/5; 5/6; 6/+
Hyacinthus hybrids 14 14/15; 15/16; 16/17; 17/18; 18/19; 19/+
Lilium candidum 16 16/18; 18/20; 20/22; 22/+
Muscari armeniacum 6 6/7; 7/8; 8/9; 9/10; 10/+
Narcissus large garden hybrids 10 10/12, 12/14, 14/16, 16/+
Narcissus smaller hybrids 10 10/12; 12/14; 14/+
Narcissus bulbocodium and other small spp. 4 4/+; 4/5; 5/+; 5/6; 6/+
Narcissus pseudonarcissus and other larger spp. 7 7/+
Scilla siberica 6 6/7; 7/8; 8/+
Tulipa garden hybrids; hybrids of T. fosteriana and T. kaufmanniana 10 10/11; 11/12; 12/+
Tulipa praestans and cultivars; T. eichleri and cultivars 8 8/9; 9/10; 10/+
Tulipa small spp. including T. kaufmanniana; T. tarda; T. turkestianica 5 5/6; 6/7; 7/+

The largest grade is usually referred to as Topsize and can be specified as such.  For certain species, for biological reasons, it may be preferable to specify a smaller rather than a larger bulb or corm, e.g Cyclamen spp., Gladiolus spp.  Also it is worth noting that smaller sizes are cheaper and often very satisfactory in projects where flowering in the first year after planting is not a priority.

Bulbs are usually graded using Round Riddle or Long Slot methods.  The Round Riddle is appropriate for bulbs which are typically spherical about their circumference but less exact for Narcissus Garden Hybrids, whose bulbs are more ellipsoid.  In Britain these Narcissus bulbs are usually graded using the Long Slot method which gives a more exact circumference measure.  Due to these differences, Narcissus Garden Hybrids grown in Holland tend to be grade sizes larger than their British counterparts.  It is important to consider the provenance of the bulbs in this specification.