GROWING GIANT PUMPKINS AND SQUASH

By Len Stellpflug

 

Giant Pumpkins and Squash require 120 to 150 days from transplant to harvest depending on climate. Grower techniques vary considerably. This material is intended for NEW GROWERS. It will get you started. A world record 1061 pound pumpkin was grown in 1996. That record was broken in 1998 by a 1092 pounder grown in Canada. In 1999 the record increased to 1131 pounds by a USA grower.

SEEDS: Use Atlantic Giant seeds proven to have good genetics. If possible obtain them from an experienced grower. DO NOT plant seeds that were not properly HAND pollinated. (see POLLINATION below)

AREA: Should be well drained and have full sun most of the day. Most growers give each plant 800 to 1600 square feet. There have been pumpkins over 600 pounds with 400 to 500 square feet. In loose soil roots will travel at least 6 feet beyond the plants edge.

SOIL TEST: Obtain a soil analysis to determine PH and fertilizer needs. As a minimum determine PH. Very large pumpkins have been grown with PH's from 6.4 to 7.4. Most growers like 6.7 to 7.0 PH. Lower PH's with sulfur. Raise PH's with lime applied in the fall as it takes 7 to 9 months to complete the change.

SOIL PREPARATION: If possible, plant a fall cover crop and till at least 8 inches into the soil in the spring. Add 2 to 4 cubic yards per 1000 square feet of manure, compost, leaves, peat moss, etc. and till into soil. Some or all of this should be applied in the fall.

FERTILIZER: Experienced growers use a wide range of fertilizer amounts and mixtures. Before transplanting many growers apply more phosphorous and potassium than recommended by soil tests. Without soil tests use a balanced product like 15‑15‑15 or one high in phosphorous and potassium like 10‑20‑20. Apply 20 to 25 pounds of 15-15-15 or 30 to 40 pounds of 10-20-20 per 1000 square feet.

After transplanting fertilize around the plant with a soluble product in water as recommended. Repeat every 7 to 10 days over a larger area. In 2 weeks roots will be out 2 feet and continue to spread rapidly. Some growers folier feed with soluble fertilizers. Use one high in phosphorous (like 15‑30‑15) until plant is desired size. Then switch to one high in potassium (like 9‑15‑30).

SEED GERMINATION AND TRANSPLANTING: Between May I and May 10 soak seeds in warm water for 30 minutes. Wrap in a damp cloth in a plastic bag for 12 to 24 hours in a warm place (80 to 95 degrees). Plant 1.5 inches deep in 6 to 8 inch pots or directly in your field under plastic covers. Plants will emerge in 4 to 7 days at 80 to 90 degrees. DO NOT plant in pots more than 2 weeks before you can transplant. Two to 5 days after plants emerge, move to field positions. Protect plants with some type of minigreenhouse for 2 to 3 weeks. Avoid overheating on sunny days if you use glass or plastic. REMAY or row‑cover material can be used.

WIND PROTECTION: When plant outgrows your mini‑greenhouse, provide some type of protection for several weeks, especially on the prevailing wind side. Wind rolls vines and snaps leaves. Stake down and/or cover vines with dirt or compost every 4 to 6 days to encourage rooting and prevent vines from rolling.

PLANT CONTROL: Control direction of runners to fill your plant area. Remove side runners to have a MINIMUM of 2 feet between runners. Growers have had large fruit with as few as 200 leaves and with over 2000. A good range is 400 to 600 leaves per plant. When plants are desired size, terminate and bury 2 to 3 feet at the end of runners about 3 inches deep. Every 4 to 6 days remove new growth within the plant.

WEED CONTROL: Hoe or rake out small weeds. Do not hoe or cultivate very deep close to your plants. Roots will be out further than the plant. If you see white roots you are disturbing the soil too deep. With runners at least 2 feet apart, weeds can be controlled with a light raking between runners every 4 to 6 days.

WATERING: These plants need I inch of water every 5 to 7 days from rain or other sources. Some only apply water on the ground and others use overhead sprinklers. Water enough to have steady growth to reduce fruit splitting. The area within 5 to 8 feet of the main root needs more water than the rest of the plant.

POLLINATION: Pollinate fruit during the first half of July. Large fruit have been on main, back and side vines. Try to pollinate one plant with another to improve genetics. Female blossoms ONLY open one day for 6 to 8 hours between sunrise and about 2 PM. When a small fruits flower opens, pick 2 to 4 male flowers that opened that morning. Remove the male flower petals so you have a 4 inch stem and the stamen. Gently rub the male stamens on all segments of the female stigma. If possible, cover the female and male flowers the night before to avoid bee cross contamination. After pollination recover the female for 24 hours. Pollinate 3 to 5 fruit per plant and select the best I or 2 when about basketball size. Some fruit will not set when temperatures are above 88 to 90 degrees. You can let bees pollinate but you risk getting mongrels from the seeds. Remove all small fruit after you have 3 to 5 fruit set.

STEM STRESS: As the fruit grows the stem rises and the tap roots hold the vine down. To prevent the stem from breaking you must provide slack in the vine. When you pollinate, slowly curve the runner 80 to 90 degrees away from the fruit. About 3 feet past the fruit curve the vine back in the general direction it was headed. Remove all side runners from one leaf joint ahead of the fruit to 2 leaf joints after the fruit. As the fruit grows cut tap roots near the stem so the vine can easily rise. Some fruit push the vine backwards and you may need to slide the fruit a little to avoid vine kinking. Think BIGP Make the "S" curve large enough for a 5 foot wide Pumpkin.

FRUIT SHADING: Shading reduces skin cracking, delays maturity and may reduce splitting by avoiding elevated fruit temperature. Its optional but recommended to shade your prize fruit from direct sun before it has 100 inch circumference.

HEAT STRESS: Heat stress (leaf wilting) occurs when the sun is intense and compounded with low humidity. Some growers cool their plants with overhead sprinklers on hot afternoons. Wetting leaves every 45 minutes is effective.

INSECT CONTROL: Cucumber Bugs: Watch for them on your small plants. They can devour your plants in a few hours. Sevin, Thiodan, Admire and Guthion are some of the pesticides that kill them. Rotennone is used by some organic gardeners.

Squash Vine Borers: From late June to early August borer moths lay eggs on and under runners and on leaf stems. You can not kill the adults as they don't eat. They are energized by the sun. You must kill the larva as they hatch. Spray the main trunk and runners every 5 to 7 days with any of the pesticides mentioned above. Aphids: Look for aphids under the leaves. You must get Malathion, Thiodan or other aphid pesticide directly on the aphids to kill them.

MILDEW CONTROL: Atlantic Giant pumpkins are not as prone to mildews as regular Pumpkins. If it is a problem, good insect control will minimize spreading these diseases. Use fungicides like Ridmil‑Bravo, Daconil, Bayleton, Benlate‑Manzate or a combination vegetable disease control product as recommended on the package. Some of these products are expensive and may require a permit to buy and use.