Answer: Pumpkin vines normally produce male blooms first, then begin produciong female blossoms as well. So the first blooms will not develop pumpkins because they are male. If the female blooms are not developing fruit, then you may need to help with pollination. To do this you can use a soft paintbrush and just move it from male to female blossoms. The vines will produce better if they are growing in rich soil that is evenly moist yet well drained -- it should be damp like a wrung out sponge. Overly dry soil can cause the blossoms to drop prematurely.
Soil preparation is usually the most important factor in success with perennials, followed by correct watering and mulching while they become established. Planting technique can also make the difference. Often, stunting is caused by poor rooting. This can be due to poor soil conditions, lack of water, or encircling roots that were not cut at planting time for example. I would suggest you work with your local county extension to run some basic soil tests and review your preparation and planting procedures. They may also be able to suggest which perennials would grow best under the planting conditions you have -- it is possible the plants you ordered might not be expected to grow well in your climate/soil/planting site. Good luck with your perennials!
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