Answer: Degroot's Spire is a smaller plant and so technically will require less water than the other arborvitaes. The plants you mention will grow deep roots if watered deeply while they're becoming established. Grown in the ground, Degroot's Spire will appreciate a deep soaking once each week during the hottest months of the year; grown in a container, it will need more frequent applications of water.
Hope this answers your question!
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