PRODUCTION OF TULIP BULBS. 17 
economic loss of the bulbs left in the ground there is the added dis- 
advantage of fouling the land. There is no crop which will foul the 
soil worse than a bulbous one if the digging is carelessly done. The 
undug bulbs persist. They come up as weeds in the next crop and 
mix varieties in subsequent years. It is a good practice to go over 
the fields about blossoming time and dig out all bulbs of the previous 
crop. This can be attended to at the time the general roguing occurs. 
ANNUAL DIGGING IMPERATIVE. 
In the commercial production of tulip bulbs the writer has seen 
no condition under which it is economically advantageous to leave 
the bulbs undug for two seasons. Such a practice can not be defended 
except on the basis of expediency; never on the basis of quality or 
production. The tulip is a gross feeder, and the commercial varieties 
are so productive in increase of small bulbs that when not lifted 
annually they are crowded to such an extent that they deteriorate 
in size and are not merchantable when lifted. (PL III, Fig. 2.) 
The only condition under which it is considered at all permissible 
to leave tulips undug is when stocks are being worked up from small 
sizes and no marketing is contemplated at the next digging. Even 
in such a case, when the increased weed burden, greater danger of 
injury from field mice, greater loss from winter heaving, and more 
laborious cleaning are considered, it is a questionable practice. 
It is estimated that the cleaning of biennially dug bulbs takes 
about three times as much labor as bulbs dug annually. The 
accumulation of old coats and the thick mat of roots make the clean- 
ing a very laborious process. 
DROPPERS. 
Tulip bulbs, like many other bulbous stocks, when not planted at 
the level which they like seek that level by a special process which 
has been named "dropping." (PL XI, Figs. 3 and 4.) This signifies 
that in the usual artificial handling the bulbs are not planted at the 
depth which is natural for them. They therefore seek the level 
which is best suited by dropping or, in some instances, when planted 
too deep, rising to it. This shift in depth is more likely to occur 
with the smaller sizes of bulbs and is more prevalent in some species 
than in the garden varieties. 
The change of location is accomplished by a simple contrivance 
which looks exteriorly like a short stem connecting the location 
where the bulb was set with its newly acquired position. In reality 
this connection is simply a fold in the leaf stem which surrounds the 
new bulb. This fold lengthens, forming a tube, in the end of which 
the new bulb develops. At times the whole original bulb drops, but 
most commonly some bulbs are formed in the original situation and 
102949°— 22— Bull. 1082 2 
