Gordon Johnson, Extension Vegetable & Fruit Specialist; gcjohn@udel.edu
Growing spring broccoli to acceptable commercial quality standards is a challenge on Delmarva. We are currently repeating for a second year a spring broccoli variety trial at the University of Delaware Georgetown research farm with 24 commercial varieties and several experimental lines to evaluate adaptation of these varieties for spring planting under high density for
Temperature variability is the main challenge for spring broccoli. Broccoli is a cool season plant and is best adapted to areas with consistent temperatures during head development where days are warm, not hot, and nights are cool. On Delmarva, high temperatures during head initiation in the spring leads to abnormal floret development. Temperatures more than 88°F can cause damage to florets in sensitive varieties. More heat tolerant varieties have been developed and are being tested again our spring trials.
This spring has been cool in general; however, there was a 3-day heat spike over 88°F on May 2, 3 and 4 that may have challenged some broccoli plantings. In our early April transplanted broccoli, we saw significant variability in head quality and head disorders between varieties. A second planting was made in mid-April and quality so far has been good on many varieties. Harvest has started on a late April transplanted test with quality being remarkably good.
June has been relatively cool and development has been slowed in broccoli, avoiding another common problem of rapid bolting in high temperatures in spring broccoli in our region. High temperature in later head development causes broccoli to advance so quickly that the crop often flowers before it can be harvested. This reduced harvest window can be a challenge to manage as heads can go from marketable to unmarketable in as little as 24 hours when temperatures are in the 90s.
Lieutenant broccoli has performed well in 2018 spring trials.
A Bejo variety doing well in a late planting
A Seminis variety also performing well in the late April planted trial in 2018.