How To Grow Giant Pumpkins...If You Dare!

Photo: Bernadette Durbin

The unusually cool days we are having this late in spring is a great opportunity to extend the planting season for pumpkin seeds. The mild weather (yet warming soil) gives the seeds a good chance to germinate. After all, the instructions, "keep the seed bed evenly moist" is much easier to accomplish when the high temperatures are in the 70's. Typically, late May-early June highs are closer to 95.

For most families, growing pumpkins that top out at 18-20 pounds is perfect for display or carving. If this is your goal, good varieties include Cinderella, Fairy Tale, Magic Lantern, Sorcerer, Jack-O'-Lantern, Connecticut Field, Ghost Rider, Orange Smoothie and the white Lumina.

Photo: Bernadette Durbin

But for you masochistic, large-space gardeners with a yearning to grow pumpkins that are of ugly, hernia-inducing size (not to mention time-consuming), here are some tips for growing giant pumpkins:

Photo: Bernadette Durbin

Buy fresh seed.
Giant pumpkin choices include "Atlantic Giant", "Big Max", Howden or "Prizewinner". Most will average 100-200 pounds when mature, except Howden, which maxes out at 40-50 pounds. If your local seed rack doesn't stock these varieties, other possible sources include Lockhart Seeds in Stockton (209-466-4401) as well mail order seed companies Burpee, Territorial Seeds and Harris Seeds. Expect to pay more for these seed varieties; for example, 15 Atlantic Giant pumpkin seeds from one catalog costs $2.75.

Choose the right location.
 Plant these giant pumpkin seeds away from other pumpkin varieties. Cross-pollination could inhibit your giant pumpkin's growth potential, so isolation is necessary. For maximum growth, plant in an area sheltered from hot, dry winds. 

Use lots of aged steer manure.
Work at least one shovel full into each mound; rototill in at least a dozen shovels full of manure surrounding the mound because every place the vine touches the ground will result in more roots. 

Plant on raised mounds, three to five seeds per mound.
Thin each mound to the two most vigorous plants after they are a couple of inches tall. Space the mounds twenty feet apart to allow room for the vines. Plant in late May. 

Feed each plant every ten days with a diluted fertilizer solution containing a 5-20-20 or a similar formula that encourages fruit formation, not leaves and vines. 

Water plants at first sign of wilt in hot weather, that could be as much as every day. Don't overhead water; wet leaves encourage disease. 

Control squash bugs and beetles by hand-picking or with a portable vacuum. 

As the plant grows, cut off most of the vines except the one with the first (or the most vigorous) fruit that appears. Do this for each plant. Tie off the amputated vine ends with string to prevent insects from entering the vine. Remove all blooms regularly to prevent further pollination so that the plant directs its energy to the one remaining pumpkin. 

Place a board under the pumpkin to help avoid rot. 

Invite several strong friends over in October to help move your masterpiece.