Vegetable Transplant Production
Watermelon Transplant Depth: Can It Make a Difference?
by Charles Vavrina
Research from North Carolina in the late 1960s indicated larger yields in once-over-harvest
cabbage can be obtained with deeper transplants. So might deeper planting of watermelon
transplants prove beneficial for Florida growers? To answer that question, studies
were conducted over three spring watermelon crops to assess transplant depth effects
Due to variability (legginess) within the transplants from year to year, researchers
used the physical positions of the top of the root ball and the cotyledon (seed
leaves) as depth markers.
In only one of the three years studied did deeper planted watermelon transplants
result in a significant yield difference - and then only at first harvest (p=0.07).
Visitors to the spring 1993 SWFREC vegetable field day will attest to the added
vigor and greatly increased size displayed by the deeper planted plants. However,
dramatic yield differences were not apparent.
As with pepper transplants, deeper planting of watermelon "tends" to advance plant
maturity, resulting in greater early yields, with no apparent effect on total yield.
No differences in individual fruit weight were noted in any year; therefore, the
increased yield resulted in more fruit.
Deeper plantings seem to reduce the stress exerted by wind on young plants. This
factor may explain the increased growth in vine and foliage noted in the field.
More vigorous growth in the first 30 days or so also may be an advantage in combating
Although all of the 1993 plants went through the "storm of the century " with few
losses, the deeper plantings seemed to recover more rapidly.
This transplant depth work has not received the broad geographical testing that
the pepper study did. Although the data are not convincingly strong to warrant wholesale
conversion to deeper planting, watermelon growers statewide are encouraged to try
a block of cotyledon depth planting.
Commercial transplant growers generally do a good job of keeping plants short and
stocky. However, if your plants prove to be leggier than you would like, do not
hesitate to plant them deeper. Studies so far have not tested even deeper plantings
(first true leaf or greater) but will this season.
Table 1. The effect of watermelon planting depth on yield in CWT/A*
|* Values followed by the same letter are not significantly different
** Losses to gummy stem blight resulted in only one harvest.