Some squash varieties bloom only during one two- or three-week period in the plant's lifetime. Growing conditions over the first part of the plant's lifetime determine whether those blooms will be a perfect blend of male and female or a fruitless display of unisex flowers. By the time plants do blossom, the pattern has already set. Prepare the garden for a good squash harvest by beginning the year with the right plan.
Choose the right squash variety for the garden space. Crowded conditions cause squash plants to produce more male flowers. Extreme stress may result in only male blossoms. Select bush varieties of squash for gardens with limited space.
Plant a full row rather than two or three plants, especially when growing hybrids. Hybrid squash produce larger numbers of female blossoms than do open-pollinated squash. As many as half the plants may be totally female. Increase the number of plants to increase pollination chances.
Fertilize the squash with 1 or 2 tbsp. 6-10-10 NPK fertilizer tilled into the hill before planting. Scatter 1 tbsp. ammonium nitrate (33-0-0) fertilizer per hill to the sides of the plants above the root zone when plants first bloom. Repeat the side dressing three weeks later for vining squash, but not bush varieties.
Plant squash at the proper spacing. In intensive plantings, reduce the width of walkways between rows but don't completely eliminate them. Squash need abundant light and good ventilation.
Thin squash plants mercilessly. Hybrid plantings normally producing 50 percent all-female plants revert entirely to monoecious (male and female blossoms on the same plant) in crowded conditions with four to five plants in one hill.
Weed squash plants regularly. Competition from weeds reduces soil nutrition and light. Shade and crowding reduce the numbers of female blossoms squash plants produce.