Munchkin
Ornamental Pumpkin (Squash) in the US

Now, these are proper squash plants, part of the Cucurbitaceae family, so they like it warm. You can start them indoors 2 to 4 weeks before your last expected frost, or direct sow seeds straight into the ground once the soil has really warmed up. For folks in Zone 5, that's usually May; Zones 6 and 7 can start in April or May; and if you're in Zone 8 or 9, March or April is your window. Plant seeds about an inch (2.5 cm) deep, in a spot that gets plenty of sun. You won't find plug plants for these generally, so it's all from seed, which is fine by me.

Once your seedlings are up, if you've started them indoors, make sure to harden them off gradually before planting them out. They're tender, so wait until all danger of frost has passed. These plants get big, proper big, so give them plenty of room, at least 3 to 6 feet (1 to 2 meters) between each plant. You can plant them in mounds, or let them trail across the ground. Some of the smaller ones can even be encouraged to climb a sturdy trellis if you fancy.