Garden tips: Pumpkin definition not that simple

Ever wonder what's the deal with giant pumpkins?

This year, the first-place pumpkin at the Washington State Fair in Puyallup weighed 1,609.5 pounds and was grown by Stan Pugh of Puyallup. Purists might argue that these are not really pumpkins but a different type of winter squash. I tend to agree, but the term pumpkin is subjective.

The winter squash that folks typically call pumpkins and use for making jack-o-lanterns have smooth, deep orange skin. The fruit is somewhat ribbed, and the stems are furrowed and woody. Botanically, they are members of the genus Cucurbita and the species pepo. Cultivated varieties (cultivars) of what I call pumpkins are a subgroup of Cucurbita pepo. Other subgroups of C. pepo include summer, acorn, spaghetti and delicata squash, as well as ornamental gourds.

The gargantuan giant pumpkins grown for fairs and festivals across the country are a subgroup of a different genus, Cucurbita maxima. They are winter squash that tend to have light orange skin with ribbed fruit. Their stems are spongy without ribs. Other winter squash in C. maxima include blue Hubbard, banana, buttercup, turban, delicious and Kabocha squash.

Another species of winter squash, Cucurbita moshata, has some cultivars dubbed pumpkins. Generally, C. moshata pumpkins have deeply ridged stems that flare out at their base. The skin may be orange, buff or green, and the flesh is dark orange and dry. These are used for making canned pumpkin and pumpkin pie. Butternut squash is in a different subgroup of C. moshata.

Each fall, my children and grandchildren delight in carving pumpkins -- the type I call true pumpkins. They go to a lot of work digging out the gooey guts and carving. It seems a shame that pumpkins start to shrivel and mold within days, and are usually goners a week after carving.

The carved surfaces allow easy entry to mold and rot fungi into the flesh. One simple step in preserving pumpkins is placing them where they will stay cool and out of direct sunlight. Expert carvers recommend storing prized specimens in the refrigerator to slow the decay process. Carvers also recommend against placing pumpkins on concrete because this will draw moisture out and lead to faster shriveling.

An Illinois Extension educator suggests dunking or spraying the cut surfaces with a 20 percent bleach solution and blotting it dry. However, she did not offer proof that it works, so I have my doubts.

There is also a product called Pumpkin Fresh available online. It contains a borax solution, and it says that it fights mold and rot. The product is daily sprayed on the inside and cut surfaces of a pumpkin.

I did find the results of a school science project where a student tested bleach and Pumpkin Fresh against a control. The winners in longevity were the control and the Pumpkin Fresh. However, after two weeks, both were just as badly shriveled because of moisture loss.

If you decide to give Pumpkin Fresh a try, let me know how it works. Of course that means carving two pumpkins, one to be used as a control and one for testing the product.

-- Marianne C. Ophardt is a horticulturist for Washington State University Benton County Extension.

This story was originally published October 3, 2014 at 12:00 AM with the headline "Garden tips: Pumpkin definition not that simple ."