By Sharon Motomura
University of Hawaii at Manoa College of Tropical Agriculture and Human Resources Komohana Research and Extension Center, Hilo
This time of year, pumpkins can be seen all over the place in Hawaii and the United States. Pumpkins are native to the Americas and flesh and seeds were widely used by Native Americans as food. Pumpkins are related to the gourds, cucumbers and melons that we all enjoy. There are basically four species that we consider to be pumpkins in the world, Cucurbita pepo, maxima, moshata and argyrosperma.
Cucurbita pepo is used as the traditional Jack-o-lantern and pie pumpkins and also includes all of the soft skin summer squashes. All have a hard woody stem at maturity. In general, C. pepo is also the most disease- and insect-susceptible of the pumpkins. Cucurbita maxima can get very large, and prize-winning, large pumpkins are from this group.
At the recent Hawaii Island pumpkin contest, the winner for the largest pumpkin was a C. maxima grown in Waimea and weighed over 600 pounds. They are characterized by having a spongy cork-like stem, they store relatively well and include all of the winter squashes like the Buttercup and Hubbard. Cucurbita moshata are the best keepers in terms of storage and their flesh is often orange and sweet and has the most refined culinary qualities. They can be identified by their smooth, deeply ridged stem. Common members include the Butternut and Cushaw. Cucurbita argyrosperma normally have pale yellow- to cream-colored flesh, not very sweet and typically grown for its seeds. It has a characteristic enlarged hard corky stem.
To try your hand at growing your own pumpkins, here are some general pointers. Pumpkins are heavy feeders and drinkers, and to grow the best fruits, a well-prepared bed is essential. To begin, find an area with full sunlight, good drainage and air movement. Dig a planting hole that is 24 inches in depth and twice as wide. Add aged manure and/or compost, fertilizer with superphosphate and incorporate into the soil. Plant three to five seeds about 1-inch deep and about 6 inches apart and cover lightly with soil. Water the plants two or three times a week, but be mindful of the weather, don’t over water. It is important while the vines are becoming established to keep weeds under control; hand weeding, mulching, or using weed mat can help. The pumpkins generally are ready to harvest three to four months after planting, but variety differences can double the time needed.
Once seedlings have two or three leaves, you will want to thin down to one or two plants about 1 foot apart and fertilize every four to six weeks with something like 10-20-20 fertilizer. Pumpkins have male and female flowers on the same plant and the first to appear are the male flowers. These blossoms are great eating deep fried, and with stuffing even better. The female flowers will appear later and are identified by the immature fruit directly beneath the flower. Hand pollination may be required in cases where pollinators are not present. This can be done by picking a blooming male flower and transferring pollen to the stigma of the female flower.
A common insect pest of pumpkins is the pickleworm, which likes to feed on blossoms as well as burrow into fruit and shoots. Using insect netting can help keep them out but will also prevent honeybees from getting in and pollinating. If you are going to be hand-pollinating the flowers yourself then this won’t be an issue. A common disease of pumpkins is powdery mildew which is fungal disease that thrives in high humidity environments with little rainfall. You may notice white fungal growth on the leaves, petioles and stem of the pumpkin. Avoid watering foliage to help minimize spread.
Determining when to harvest your pumpkin may be tricky. It may be time to harvest when you notice the skin lose its sheen, the tendrils die or when the fruit stem becomes woody. One rule of thumb is the use the fingernail test. When the fruit resist puncture by your thumb nail, the fruit is ready to harvest. When harvesting, make sure to leave the stem attached, as this will prolong its storage. An open stem scar can be an open invitation to disease and insect infection. As a reminder, the stem, as convenient as it may appear, is not a handle for which to handle the fruit. To increase the life of your pumpkin, it is best to place your pumpkins in a curing area (well ventilated and no direct sunlight) for a week to 10 days. Curing aids in the healing of wounds and toughening of the rind.
Now it’s up to you to decide what to do with your pumpkin, be it a jack-o-lantern or pie, decorating for trick-or-treater’s or the Thanksgiving feast. As a historical note, the pumpkin pie of the pilgrims was more like pot pie. The top of the pumpkin was cut open and the seeds removed. The hollow was then filled with fruit, spices, sugar and milk and, with the top replaced, baked on wood coals. Pumpkins are very nutritious, and their bright orange flesh is full of beta carotene, a precursor to vitamin A. Pumpkins are also a good source of potassium and dietary fiber. Here is a recipe for good old pumpkin pie to get you started. Happy Halloween! To download recipes using pumpkin and other vegetables grown in Hawaii visit: http://www.ctahr.hawaii.edu/oc/freepubs/pdf/B-97.pdf
For more information on home gardening please visit the East Hawaii Master Gardener Program website at http://www.ctahr.hawaii.edu/uhmg/EastHI/index.asp or visit any of the local Cooperative Extension offices around the island.