Smithsonian.com

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The other day, I called Thomas Andres, a researcher at the New York Botanical Garden, with a clear agenda. What advice, I asked, do you have when it comes to pumpkin carving? Do you have any tricks up your sleeve to keep jack o’lanterns in good condition through Halloween?

Andres is a cucurbitologist. Translation: He is a pumpkin expert. And, in the first five minutes of speaking with him, the man had me convinced that the pumpkin is a work of art, even before you get to the carving.

Cucurbitaceae is the family of gourds, pumpkins, watermelons and cucumbers, explained Andres, and within that family is the genus Cucurbita, his expertise. All of the pumpkins we display on our doorsteps at Halloween are from this genus, and most of them are one species. “The typical jack o’lantern is Cucurbita pepo,” he says.

Squash breeders have cultivated five species, Cucurbita pepo included, to fit our notions of the perfect pumpkin. “They have bred for the thickness of the fruit stem. Wild pumpkins are very spiny plants. So, they have tried to breed out and get rid of the spinyness,” says Andres. Cultivators also select for a bright orange fruit and nice, dark green stems. “That seems to attract people,” he says.

When Andres carves pumpkins, he personally does not take any measures to prevent them from rotting. “It gives them character,” he says. That said, if you’d like to keep your jack o’lantern from slumping and growing a little fur, he does have a few tips:

1. First and foremost, pick a pumpkin that is hard. Also, make sure that it has no blemishes. “You don’t want them to have any frost damage,” says Andres. “You can tell that by looking at the fruit.” Watery dark spots on the top of the pumpkin are an indication of frost damage.

2. “You want to wait until the last moment before carving pumpkins,” says Andres, since they tend to rot within a week or so. “But once you carve them, there are a few tricks to making them last a little bit longer.”  You can squirt lemon juice on the exterior of the pumpkin, for instance. Lemon juice, as you may know, prevents the browning of fruits, such as apples and avocados (and pumpkins!). The browning is a result of phenols and enzymes in the fruits reacting with oxygen, but acidic lemon juice blocks the enzymes and thereby inhibits the reaction. Vaseline or vegetable oil can also be applied to preserve the pumpkin once it is cut.

3. Spray the jack o’lantern with a bleach solution, to stave off fungus growth.

4. Keep the pumpkin away from freezing temperatures. If it freezes, the pumpkin will thaw and inevitably rot.

5. Temperatures from the upper 50s to lower 60s (in degrees Fahrenheit) are ideal. When outdoor temperatures stray too far from this, think about bringing your pumpkin indoors. “If you really have a prize-winning carving, and it is not too big a fruit, you could put it in the refrigerator when it is not on display,” says Andres.

Ray Villafane and one of his pumpkin sculptures from 2011. Courtesy of the New York Botanical Garden.

Last weekend, master pumpkin carver Ray Villafane turned some massive pumpkins on display at the New York Botanical Garden into zombies. Staff are refrigerating some of the sculptures’ removable parts, at times, to keep the carvings fresh during the ten days they are on exhibition.

6. Keep the pumpkin away from extreme heat. “As nice as candles in jack o’lanterns are, they really do shorten the lifespan of the pumpkin since the heat from the flame ends up cooking the flesh,” says Andres. “A flickering lightbulb or glow-stick can be used instead.”