Ask Dave Epstein: What is the autumnal equinox?

Meteorologist Dave Epstein is our go-to person for pressing weather questions on everything from winter blizzards to summer droughts. He’s also a horticulturist, meaning he’s an expert on anything that grows leaves and flowers. GBH's Morning Edition asked you, our audience, for your weather and gardening questions, and Dave graciously answered them on the air. This transcript has been edited for clarity.

Have a gardening or weather question for meteorologist Dave Epstein? Tweet him @GrowingWisdom, email us at thewakeup@wgbh.org, or text 617-300-2008.

Tonight we reach the autumnal equinox. What exactly does that mean?

As it turns out, there are many first days of fall. Solar autumn, when the amount of sunlight in a day starts declining rapidly, starts in August. And climatological autumn, when temperatures start falling, starts in September.

But the day people usually mark is autumnal equinox, which this year falls on Sept. 22 at 9:03 p.m.

“Now we have astronomical autumn, which is when the Terminator — not the Arnold Schwarzenegger character, but the Terminator, which is the line that marked day and night crossing the planet. [It’s] vertical, so it goes directly from the North Pole to the South Pole,” Epstein said. “In that moment, if you are on the equator, the sun would be directly overhead. That's what it means. It's a marker of time.”

How is the local apple picking this year? And what is the best time to go apple picking?

Now’s the moment, Epstein said.

“The best time is actually any time you can go now in the next few weeks,” he said. “Find out what time the orchard opens, get there then, get your apples picked and get home and make a pie or something like that.”

This year’s drought means apples are smaller, but flavorful.

“If folks didn't have a ton of irrigation, they're going to be a little smaller. I think that's one of the things you'll notice. If you remember the apples last year, they were huge because of all the rain,” he said. “But you know, I had some Honeycrisps here a couple of days ago and they were absolutely delicious.”

What’s the best place to go leaf-peeping?

Like the apple crop, leaf peeping will be different because of this summer’s drought, too. Some trees are already losing their leaves because of a lack of water, and others have browning leaf tips instead of brilliantly-changing colors.

But fear not: There are still good places in New England to see the leaves change. Northern New England got more rainfall through the summer, and also tends to have a higher concentration of the always-extraordinary maple trees, Epstein said.

Massachusetts has good spots too: The Berkshires, northern Worcester County, and even along Route 128, driving from the Mass. Pike up through Burlington and Lexington and heading toward Woburn.

Esptein also recommended taking the I-95 up to Portsmouth.

“If you just look on the highway, there's a lot of variety of trees there,” Epstein said.

How do people grow those giant pumpkins?

There’s an art to it, Epstein said. It involves selecting seeds from other giant pumpkins that are bred only for size. Growers typically start their pumpkins early, in greenhouses or small hoop houses where they can keep the soil warm.

Epstein mentioned his friend, WGME meteorologist Charlie Lopresti, who has fed his giant pumpkins milk to help them grow.

“It's the genetics of those pumpkins that make them large, like, they're not made for eating or anything else,” Epstein said. “They can grow 50 pounds in a day at the beginning — and it can be really sad because sometimes they can grow too quick and they can split.”