http://breezewiki.bunny5exbgbp4sqe2h2rfq2brgrx3dhohdweonepzwfgumfyygb35wyd.onion/minecraft/wiki/Melon
Melon stems connect only to the melons they produce. For example, if stem A generates a melon adjacent to stem B, stem B does not connect and can still produce another melon. Similarly, if a melon is placed adjacent to stem B, stem B would still be able to produce another melon.