Buy living lettuce. Usually sold as Organically, Hydroponically grown lettuce. Clip off outer leaves and use. Leave the core leaves intact. Place in a glass of filtered water for a few days in a window sill. Trim off less lively leaves. Plant in rich soil up to base of core leaves. Plant should last through many cuttings as long as you cut from the outer leaves and leave a small inner core. Love the sweet tender butter lettuce. The plastic shell makes a good seed starter atrium as shown. Enjoy!
Pam's Tactical Kitchen 
I was thinking of leaving the central part of the lettuce with root ball on my sunny window sill. Can it grow in just water?
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I really don’t know, try it, and let us know.
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yes it can it takes a few weeks but yes
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I tried but it not live past a week in just water and did not have any new growth.
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