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Soil preparation
Pumpkins should not follow after other cucurbits or nightshades because of the risk of blight caused by Phytophthora capsici. They follow well after cole crops, and leguminous green manures or sweet corn.
Where Phytophthora (Phytophthora capsici) is an issue, rotate away from this land. Biofumigation has shown some effectiveness to reduce incidences.
Apply compost and other amendments based on the results of a soil test.
Spread lime as needed to increase both the pH and Ca levels. Dolomite lime will also increase Mg levels. Spread gypsum when calcium levels are low but pH is correct.
Incorporate compost, and plant pumpkins in raised beds or grow them as a field crop.
Common recommended fertilizer rates1
Nitrogen
Phosphorus
Potassium
pH
100
0-160
0-160
6.0-6.4
1Rates are for New York and are from Cornell University’s Nutrient Guidelines for Commercial Vegetable Production (2019). Check the Cornell website for updated guidelines, or consult with local experts for recommended rates outside New York.
Use a 1020 tray with 24 pots for more light, which results in stockier plants. When using a 38-pot tray, make sure you transplant before they get leggy.
Cell pack tray
Germination temp
Growth temp
Hardening off
Notes
24 or 38
75°
75°
Withhold water
3–4 seeds to a cell. Put plug trays on a wire mesh bench to encourage air pruning. Take plants outside 1 week before planting in field.
Signs to watch for and what to do
Pumpkins grow fast. Make sure to transplant them to the field before they get leggy.
Transplant readiness indicators
Harden plants off outside; plants that are lush don’t perform well in the field.
Transplant in the field when plants have enough of a root ball to hold the soil in the pot or cell pack together. When they can’t, their roots will be damaged and the plants have a higher fatality rate.
Transplant tips
If using plastic mulch, lay it at least a week before planting to allow weed seeds to germinate and the soil to warm. Planting on the same day as laying plastic will cause weed pressure in the planting hole.
Avoid transplanting in plastic mulch during the heat of a hot summer day. The heat of the plastic can cause damage to the young seedlings. To avoid burning the young plants, transplant in the evening, use stocky transplants and water deeply. If planting by hand, water plants with a watering can. Avoid applying row covers in hot conditions. When hot weather is expected after transplanting, only use insect cover for protection.
To help resist cucumber beetle damage, dissolve Kaolin clay (as in Surround) in plenty of water and drench the complete tray in the solution before transplanting.
Water wheel planter
Rows
In-row spacing
Planting depth (inches)
Notes
1
12 inches
Same level as potting medium
Direct seeding information
Seeder
Rows
Seeds per foot
Seed plate no.
Depth (inches)
Sprocket setting
Notes
MaterMacc
1
1
9 H 4.5
1/2
22-18
Cultivation procedures (without plasticulture)
You can use your regular cultivation setup with side knives if growing pumpkins in the traditional bed system. Don’t use any finger weeders. Precision cultivation can damage cucurbits. Keep some distance from the plants to avoid this.
You can use a regular field cultivator and drive between rows if you planted pumpkins 10–12 feet apart.
Hand hoe between plants.
Cultivation procedures (with plasticulture)
When using plasticulture, plant at least a week after laying the plastic mulch, to allow weeds to germinate under the plastic. Use infrared transmitting (IRT) plastic to warm the soil earlier in the season.
After transplanting, cultivate once or twice in between plastic with a rolling cultivator or Spyder. Cover the wheel tracks with rye straw at a rate of 3 lbs. per foot. (One 600 lb. round bale covers 200 feet of wheel track.) Increase this amount when using an early cutting of orchard grass, because hay breaks down much faster than straw. Over time, hay and straw mulch will release a significant amount of K and other beneficial properties like silicon, contributing to long-term soil health. Mulching also protects crops from soil splashing. This reduces soilborne diseases and time spent cleaning produce after harvest.
Frost, disease and insect protection
Plant upwind from early plantings of other cucurbits such as summer squash or melons, as both powdery and downy mildew are windborne.
Use floating row covers or insect covers to protect against frost and striped cucumber beetles. For varieties that require pollination, remove the covers at flowering. Use 10-gauge wire to support the row cover, since abrasion against the cover will damage the plants. If frost protection or providing a warm environment isn’t necessary, you can use the longer-lasting insect covers to provide protection against beetles.
Keep squash bug populations under control by rotating far from where you grew squash the previous year. Unfortunately, squash bugs will shelter in the straw between plastic mulch.
Powdery mildew: The best way to avoid losses from powdery mildew is to use tolerant or resistant varieties. Powdery mildew can be somewhat controlled with a mixture of Bacillus subtilis, as in CEASE, and potassium bicarbonate, as in MilStop SP. Sulfur causes phytotoxicity in melons, so be careful if you’re applying sulfur in any form to control powdery mildew.
Downy mildew can be somewhat controlled with the biological control Pseudomonas aeruginosa, as in Zonix. Also, consider using tolerant or resistant varieties.
A full list of OMRI-listed control products available for cucurbits, and their efficacy, is available from CALS.
Other cultural practices
Irrigate frequently for optimum yield and plant health. Frequency depends on soil type, evaporation, precipitation and the particular needs of the crop.
Double cropping and/or cover cropping
Incorporate any remaining plants, weeds and fruit into the soil. Plant a cover crop like rye and vetch to reduce future squash bug populations.
If weed pressure was high and caused a lot of seed rain, it’s better to refrain from any fall tillage. Allow the weed seeds to decay and be eaten by birds and rodents over the winter months to reduce future weed pressure. Unfortunately, this is contradictory to keeping squash bug populations under control.
This material is based upon work that is supported by the National Institute of Food and Agriculture, U.S. Department of Agriculture through the Sustainable Agriculture Research and Education (SARE) program. Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and should not be construed to represent any official USDA or U.S. Government determination or policy.
