I have been growing zucchini for years, but the last few years I have been dealing with rot at the bloom end. The whole zucchini then withers. I get a few, but not like I used too. They are in a raised bed and we water about once a week depending on the weather. What am I doing wrong? Please help!
There are three possible causes: poor pollination ( a problem in wet weather and early in the season), blossom disease (a problem in wet weather and overhead watering at night), and a calcium disorder called blossom end rot (most likely). BER is most common on poorly limed soils and is complicated by uneven moisture in the root zone. Calcium is a rather balky mineral to get into plants. If the soil around the roots dries out too much, the plant roots slow down water and mineral uptake. When the zucchini is watered again, calcium is the last mineral to be taken up. The developing roots, leaves, and fruits all compete for the calcium. The roots and shoots win and the fruits develop calcium deficient cells at their blossom end and those cells collapse and dry out. The fruit may stop growing at that point. Since raised beds end to drain better (a good thing in most situations) careful attention to even watering is a must, especially in hot weather. It is hard to add calcium this time of year but your 4 x 8 beds should be limed in the fall with about 3 pounds of lime once every three years to maintain good calcium levels. This same disorder is common on tomatoes. The advice would generally be the same. Feel free to email or call me directly if you still have questions. Chip
Agricultural Extension Agent and County Leader
Oregon State University Extension Service Columbia County
505 N. Columbia River Highway St. Helens, OR 97051
Phone: 503-397-3462 Fax: 503-397-3467