Botanical name: Cucurbita maxima, C. moschata, C. argyrosperma
Plant type: Vegetable
Sun exposure: Full Sun
Soil type: Any
- Pumpkins do best when the seeds are directly planted in the ground. However, if your growing season is very short, seed indoors in peat pots about 2 to 4 weeks before last spring frost. Be sure to harden off before transplanting.
- The soil must be thoroughly warmed. Minimum soil temperature for germination is 70ºF. Optimum soil temperature is 95ºF. Pumpkins are very sensitive to the cold.
- Pick a site with full sun (to light shade).
- Pumpkins are big greedy feeders. They prefer very rich soil that is well-drained and not too soggy. Mix lots of compost and aged mature into the planting site before you sow seeds or tranplant.
- Select a site with lots of space for the sprawling vines. Vine varieties need 50 to 100 square feet per hill.
- However, if your garden space is limited, no worries! Plant pumpkins at the edge of the garden and direct vine growth across the lawn or sidewalk. The vines will only be bothersome for a few weeks. You can also grow pumpkins in big 5 to 10 gallon buckets! Or, try miniature varieties.
- You plant seeds in rows or "pumpkin hills" which are the size of small pitcher mounds. With hills, the soil will warm more quickly and the seeds will germinate faster. This also helps with drainage and pest control.
- Prepare the hills in advance with an abundance of old manure dug deep into the ground (12 to 15 inches). If you don't have manure, loosen the soil and mix in a 2- to 4-inch layer of compost
- Plant the seeds 1 inch deep into the hills (4 to 5 seeds per hill). Space hills 4 to 8 feet apart.
- When the plants are 2 to 3 inches tall, thin to 2 to 3 plants per hill by snipping off unwanted plants without disturbing the roots of the remaining ones.
- In rows, sow seeds 6 to 12 inches apart in rows 6 to 10 feet apart. Snip off plants to thin to one plant every 18 to 36 inches.
- Use row covers to protect plants early in the season and to prevent insect problems. However, remember to remove covers before flowering to allow pollination by insects!
- Pumpkins are very thirsty plants and need lots of water. Water one inch per week. Water deeply, especially during fruit set.
- When watering: Try to keep foliage and fruit dry unless it’s a sunny day. Dampness will make rot more likely.
- Add mulch around your pumpkins to keep in moisture, suppress weeks, and discourage pests.
- Pumpkins need lots of nutrients. A regular treatment of manure or compost mixed with water will sustain good growth.
- Fertilize on a regular basis. Use a high nitrogen formula in early plant growth. Fertilize when plants are about one foot tall, just before vines begin to run. Switch over to a fertilizer high in phosphorous just before the blooming period.
- Remember that pumpkins are tender from planting to harvest. Control weeds with mulch. Do not overcultivate, or their very shallow roots may be damaged.
- Most small vine varieties can be trained up a trellis.
- Larger varieties can be trained upward on a trellis, too—though it is an engineering challenge to support the fruit—usually with netting or old stockings.
- Pinch off the fuzzy ends of each vine after a few pumpkins have formed. This will stop vine growth so that the plant's energies are focused on the fruit.
- If your first flowers aren't forming fruits, that's normal. Both male and female blossoms need to open. Be patient.
- Bees are essential for pollination, so be mindful when using insecticides to kill pests. If you must use, apply only in late afternoon or early evening when blossoms are closed for the day.
- Pumpkin vines, though obstinate, are very delicate. Take care not to damage vines, which reduces the quality of fruit.
- Pruning the vines may help with space as well as allow the plant's energy to be concentrated on the remaining vines and fruit.
- Gardeners who are looking for a "prize for size" pumpkin might select the two or three prime candidates and remove all other fruit and vines.
- As the fruit develops, they should be turned (with great care not to hurt the vine or stem) to encourage an even shape.
- Slip a thin board or a piece of plastic mesh under the pumpkins.
- Squash bugs and cucumber beetles are common. Contract your local County Extension for controls.
- Powdery Mildew
- Poor light, too much fertilizer, poor weather at bloom time, and reduced pollinating insect activity can reduce fruit set.
- Cucumber beetles and squash bugs can invest pumpkins, especially later in the summer.
- Your best bet is to harvest pumpkins when they are mature. They will keep best this way. Do not pick pumpkins off the vine because they have reached your desired size. If you want small pumpkins, buy a small variety.
- A pumpkin is ripening when its skin turns a deep, solid color (orange for most varieties).
- When you thumb the pumpkin, the rind will feel hard and it will sound hollow. Press your nail into the pumpkin's skin; if it resists puncture, it is ripe.
- To harvest the pumpkin, cut the fruit off the vine carefully with a sharp knife or pruners; do not tear. Be sure not to cut too close to the pumpkin; a liberal amount of stem (3 to 4 inches) will increase the pumpkin's keeping time.
- Handle pumpkins very gently or they may bruise.
- Pumpkins should be cured in the sun for about a week to toughen the skin and then stored in a cool, dry bedroom or cellar—anywhere around 55ºF.
- If you get a lot of vines and flowers but no pumpkins, you need more bees in your garden to pollinate the flowers.