Grow Giant Pumpkins

Watching pumpkins grow is one of gardening’s magical experiences. Tiny seeds give rise to rambling vines that can easily reach 25 feet in length. The real mystery unfolds when flowers transform into pumpkins. Tracking a marble-size pumpkin as it balloons to bowling ball size and swaps green skin for orange is pure fun.

 

At the Lowe’s Giant Garden, we’re taking pumpkin growing fun to the next level by raising giants. These heavyweight vegetables will easily surpass the giant cabbages we grew earlier in the season—in both size and weight. Maybe we’ll even coax enough weight out of our pumpkins to compete in a local pumpkin competition.

Our seeds went into the the ground June 24. The seedlings have broken ground, and now we’re waiting for vines to run, flower, and set pumpkins. Check the Lowe’s Giant Garden website for photos of the pumpkin progress so you can see how large our fruits grow. If you want to try your hand at raising a giant pumpkin, for fun or for serious record-breaking sport, now is the time to start planning and preparing soil. Follow our tips to grow your own champion pumpkin.

 

Start with good seed.

Consider genetics when setting out to grow a giant pumpkin. Traditional pumpkin seed doesn’t have the genes to grow to 500-plus pounds. You need to start with seeds from a giant pumpkin. We used the selection that has produced world champion pumpkins since 1979: Dill’s Atlantic Giant.

Site for sun.

Choose a spot for your pumpkin patch where vines will receive at least 6 hours of sun daily (the more, the better). For raising a true giant, give each vine 2,500 square feet.

Prepare soil.

Tackle this part in fall so your soil will be ready for planting next spring. Amend soil in a 30-foot diameter circle for each pumpkin vine. Add composted cow or horse manure to the soil in fall. For even more success, sow a cover crop of winter rye to be turned under soil in early spring. Take a soil test this fall and amend your soil according to the results. Pumpkins thrive in soil with a pH between 6.5 and 6.8.

 

In early spring, prior to planting, turn any cover crops into soil. Work a granular fertilizer into soil (4-6 inches deep) a few days ahead of setting out pumpkin seedlings.

Plant seeds.

To grow a truly behemoth pumpkin, sow seeds in 6-inch peat pots four weeks before your area’s last spring frost date. Seeds emerge in five days when soil temperature hovers from 85-90 degrees Fahrenheit. Transplant seedlings to the garden when roots begin to grow through the peat pot or when the first true leaves unfurl. Protect seedlings from winds and frost with a floating row cover, cloche, hot cap, or miniature greenhouse.

Beat weeds.

Use mulch to keep weeds in check. Once vines are growing and running, they’ll quickly shade and crowd out weeds. If you choose to use plastic mulch, run drip irrigation or a soaker hose beneath the plastic.

Help the bees.

Flowers will appear on vines in 8-10 weeks. Female flowers have a small pumpkin at the base of the bloom. When female flowers appear, hand-pollinate them using a male bloom. Early in the morning, pick a freshly open male flower and remove the petals to expose the pollen. Touch the pollen to the sticky internal part of a freshly open female flower.

 

Growing a true giant pumpkin requires early pollination. Aim to have pumpkins setting on vines before July 10, but don’t pollinate until vines have about 200 leaves.

Position pumpkins.

When pumpkins form, their stems typically create an acute angle with the main vine. Giant pumpkins need a stem that’s perpendicular to the vine. When pumpkins are basketball size, gently curve the vine 80-90 degrees away from the fruit. When the vine grows 3 feet beyond the pumpkin, curve it back in the direction it was originally headed before you moved it.

Choose your giant.

As pumpkins start to form, keep only 4-6 per vine. When fruits are volleyball size, remove all but one pumpkin. For a true giant, choose your keeper by measuring, weekly or daily, the circumference of each pumpkin at the widest point. Keep the pumpkin that’s growing the fastest. Round, tall pumpkins tend to grow the biggest.

Prune roots and vines.

Pumpkin vines root along the length of the vine. Clip all roots for 3 feet in either direction of your giant. Prune vines when they have grown 10-12 feet beyond a developing pumpkin. Prune side shoots off the main vine to 8 feet long. When you prune vines, bury the cut ends to reduce water loss.

Vary fertilizer.

Seedlings require more phosphorus; fertilize them using a 15-30-15 product. After pumpkins are set and growing, use a balanced fertilizer (20-20-20). Apply both fertilizers once or twice weekly as a water-soluble fertilizer. In late July, shift to a water-soluble fertilizer that contains more potassium (15-11-29). Use this product until harvest. Take care not to overfertilize your pumpkin. A giant pumpkin grows so fast that it can literally tear itself off the vine and even explode if overfertilized.

Guess the weight.

To guess-timate the weight of your giant, take three measurements. First, measure the circumference of the pumpkin parallel to the ground, from blossom end to stem. Second, measure from ground to ground over the top of the pumpkin from stem to blossom end. Third, measure from ground to ground over and across the top of the pumpkin perpendicular to the last measurement. Add the three figures together. Multiply the sum by 1.9 to obtain an estimate of the pumpkin’s weight.

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