A round container, about 13» deep and 18» in diameter does well for about three moonflower vines. I used a larger pot, say 24» deep and 30» in diameter to hold 5 or six vines underplanted with petunias. A teepee of five to six foot lengths of bamboo served as the upright but the vines grow so long that they droop back down over the supports. To make a screen I advise planting vines about 6 inches apart. Single vines can lose lower leaves it's best to allow the vines to trail back down over their supports. Use containers at least a foot deep. The roots will fill the container and you'll need to water sometimes twice daily in really hot sun/temps. Moonflower vines may grow slowly in cool temperatures but will take off when it gets warm. If not in full sun they may not bloom until late summer. You did not say what zone you are in. All my experience is in zone 6a.

Good luck. I hope you enjoy your moonflower vines as much as I've enjoyed mine. The flower scent is fantastic.

Asking questions is how you learn, Justine, and I enjoy helping a new gardener learn. I suspect a window box will not provide enough room for the roots of your moonflowers. In my experience, roots nearly fill large containers by the end of the season. I've never planted them in a small container such as a window box but I suspect any planted there would not grow as well as those with more root room. I would plant only three vines in 10 inch tall and wide pot, and I would fertilize this with a diluted fish emulsion once a week. Potted annuals can get quite root bound by the end of the summer and this is exactly the time when moonflowers should begin to shine in your zone. They really thrive in hot temps. Give your seedlings a short bamboo stick to wind around and transplant stick and all into a larger pot when the weather allows. The vines will twine around any longer supports you give them. Then expose the seedlings to bright light - not direct sunshine yet - for a few days. Move them into more and more direct sun over the next few days, then they can go into full sun.

Dont' hesitate to ask further questions ... and enjoy your moonflowers. They are one of my favorites.

Don't move any plants from inside full sun to outside full sun. The leaves will burn, just as we do when exposed to direct sunlight. Move indoor plants to an area of bright, but not direct sunlight for a few days. Then slowly expose them to direct sunlight. After about a week they should be okay in full outside sun. If it works out, try moving them to their permanent outside location during a period of cloudiness just to give leaves a little more time to adjust to full direct sun. Use this process for any plants you start inside for outside growing and for any houseplants you move outside for the summer.

The plant light should be on for 10-12 hours a day. Plant lights simulate outdoor conditions. Once it remains in the high 50's to low 60's at night, move them outside into indirect light. The hardening-off process begins when you move them outside. Just watch the temps. Moonflowers DO NOT like anything below 55 degrees. Also, don't panic if the leaves look droopy during the heat of the day - they do this. Just make sure to keep them well watered and the leaves will perk up by afternoon. The vines/flowers look best in the evening/early morning.