Members of the same family as cucumbers and melons, summer squash (Cucurbita pepo var.) are easily hybridized, and compact varieties suitable for container growing are widely available. Plant summer squash in your largest containers---2 feet deep and 2 feet wide---to accommodate their large leaves and thick stems.
Crookneck 'Early Summer'
A mild and succulent crookneck variety of summer squash, 'Early Summer' grows on a compact plant just 2 feet high. Its compact habit is easily accommodated by a large container, at least 2 feet in diameter. Summer squash varieties ripen during the hottest part of summer, and the plants must not be allowed to dry out. Check the potting soil daily to determine if watering is needed. Water when the top inch of the soil is dry.
The zucchini variety 'President' is an upright-growing zucchini that forms a compact plant rather than a vine, making it suitable for growing in containers. Plant zucchini in a container at least 24 inches deep, check the soil daily and water when the top inch of soil is dried out.
'Peter Pan' Patty Pan
A miniature "patty pan" type of summer squash, 'Peter Pan' grows on a bushlike plant that takes little space, making it perfect for container growing. Plant in a 4-gallon pot with a rich potting mix. Grow in full sun, and check the soil's moisture level daily.