There are some plants which flower much sooner if grafted from, or grown from a cutting of, an already flowering plant. So maybe that is why mulberries you get from nurseries are so expensive - they are vegetatively propagated from a mature plant. Mine had one or two flowers the first year I planted it, almost as tall as me it cost me about £40. I'm trying to stop it getting too big or I'll never be able to get the fruit. Mine's a very upright form too, I've pruned it to a lollipop standard shape. I've tried striking some cuttings off mine, but without success.

Likewise, my Metrosideros umbellata (Southern rata, hardy form of the New Zealand Christmas Tree) has flowered after just 7 years as a low lollipop-shaped bush rather than the 25 years it takes from seed, because it was grown from a cutting from a mature plant. Wonderful plant, very rare in cultivation here. It looks like some ancient gnarled stunted plant, whereas in fact it isn't. People just don't realise it is fairly hardy. Wish I could get my damn wisteria to flower - it had one flower, its first, last year so I thought it would do the biz this year, but it didn't, despite all my thoughtful pruning.