16.1
General
These standards have used the format from the American Standard for Nursery Stock and adopted the standards for bulbs from the Flowerbulb Centre, Hillegom, Holland.

For various miscellaneous bulbs and tubers not included here the standards from the Flowerbulb CentreDutch are applicable. (Write to: Technical Director, Flowerbulb Centre, PO Box 172, Parklaane 5, 2180 AD, Hillegom, Holland)

Bulbs and corms are generally sold under grade names such as forcing size, top size, large, etc. In the case of Narcissus and Daffodils the designations of “double nose” to indicate a split bulb with probably two flower buds and “rounds” are used.

The following grades conform in substance to generally accepted trade usage. Both grade names and sizes in centimetres should be given; size in centimetres must be designated.

Offers of bulbs, corms and tubers which cannot reasonably be expected to bloom in the season after planting should not be made to the public. If they are,  they should be clearly indicated as “non-blooming” sizes for naturalization or planting for which “non-blooming” sizes might be.

16.2
Tulips
Tulips are to be measured in centimetres of the circumference.

Top Size    12 cm and up
Large        11 - 12 cm
Medium    10 - 11 cm
Small         9 - 10 cm

Note:  Some botanical and other species, of tulips are smaller than the above sizes. Bulbs of these species must be identified and sizes given.

16.3
Hyacinths
Designated by centimetres of circumference.

Top Exhibition Forcing Size        19 cm and up                
Large Exhibition Forcing Size     18 - 19 cm
Medium Exhibition Forcing Size  17 - 18 cm
Top Bedding or Garden Size       16 - 17 cm
Large Bedding or Garden Size    15 - 16 cm                      
Medium Bedding and Miniature
     or Garden Size                        14 - 15 cm

16.4
Grape Hyacinths (Muscari)
Designated by centimetres of circumference.

Top Size             9 - 11 cm and up
Large Size          8 - 9 cm
Medium Size       7 - 8 cm
Small Size           6 - 7 cm

16.5
Large Flowering Crocus
Designated by centimetres of circumference.

Top Size         9 cm and up
Large              8 - 9 cm
Medium           7 - 8 cm
Small               6 - 7 cm

16.5.1
Other Crocus
Designated by centimetres of circumference

All types    5/6 cm

16.6
Narcissus And Daffodils

RD - 1 Top Size Round
RD - 2 Large Size Round

“Round” means single nosed bulbs which are circular in cross-section and which show evidence of producing one flower. Slabs are not permitted in this grade.

DN-1 Top Size Double Nose
DN-2 Large Size Double Nose
DN-3 Medium Size Double

“Double Nose” means bulbs that show evidence of producing two or more flowers.  Due to double character of bulb, the circumference measurement will vary.

There are certain varieties that normally have smaller bulbs than others. Until size grades are established, name grade designations as indicated and accepted by the trade should be used.

16.7
Narcissus (Paper White)
Paper White (A type of bulb that is normally smaller than other varieties and consequently is listed separately).  
    
Designated by centimetres of circumference.
    
Top Size         16 cm and up          
Large              15 - 16 cm
Medium           14 - 15 cm
Small               13 - 14 cm

16.8
Gladioli
Designated by centimetres of circumference.
    
Jumbo        14 cm and up
Large No.1      12 - 14 cm
Large No.2        10 - 12 cm

16.9
Amaryllis  
The size of the bulb will determine the quantity of flowerstalks produced, Jumbo size can produce 3 stalks, a 30 cm bulb can produce 2 stalks and a 20 cm bulb will only produce 1 stalk. Each stalk produces between 4 and 6 flowers.  

Bulb sizes are designated by centimetres of circumference.
Jumbo        36 cm and up
Exhibition    32 cm
Fancy        30 cm
Large        26 cm
Medium    22 cm
Small        20 cm

16.10
Lilies
Bulb sizes are designated by centimetres of circumference. Various types of Lilies produce different size bulbs. These generally fall into two groups:  the large bulb types such as “Trumpet”, “Oriental” and “Easter”; and the smaller types such as “Tiger” and “Asiactic”.

Large type bulbs    Small bulb types
24 cm and up        18 cm and up
22 - 24 cm        16 - 18 cm
20 - 22 cm        14 - 16 cm
18 - 20 cm        12 - 14 cm
16 - 18 cm        10 - 12 cm

16.11
Begonias
Bulb sizes designated by centimetres of diameter.

Giant                6 cm and up
Extra Large      5 - 6 cm
Large               4 - 5 cm
Medium           3 - 4 cm
Small               2 - 3 cm

16.12
Dahlias
The tuberous root of the Dahlia are available as;

Division, one small to large tuberous root with a portion of live crown with at least one eye or bud.

Clump, a number of small to large tuberous roots with a common live crown with at least one eye or bud.