Definition of "grower"

'The Bride' [a snowdrop variety], found in the early Seventies at Foxcote Farm near Cheltenham, was his first discovery. It's a poculiform (cup-shaped) G. elwesii with six pure white petals of the same length. Like many poculiforms […] it's not a strong grower.

2015 February 7, Val Bourne, “The quiet man of the world of snowdrops”, in The Daily Telegraph (London), page G8

Sanctury[sic] - the least obvious single but what a grower. When I first heard this track I thought it was rather average. After playing the album several times, this was the one that kept coming into my head throughout the day.

1994, Mr. S.R. Winterton, “Bedtime Stories - The Singles”, in alt.fan.madonna‎ (Usenet)

[…] assimilating some vaguely psych, folk-rock, and other influences into their own twang without losing sense of style and taste: a grower, not a shower (that's show-er, not shower).

2001, Maximum Rock 'n' Roll, Issue 223‎

As a man who can best be described as a "grower not a shower", I helped Brent realize that many people in the gay community are concerned in a very adolescent way with their dick size, including me.

1993, Barry Burns, “Muffin on Parade”, in soc.motss‎ (Usenet)

"Growers" are guys whose penises tend to contract a lot lengthwise when flaccid, while "show-ers" are guys whose penises could be said to merely "deflate" without contracting much in length.

1994, jenster, “Penis Size and other Eternal Questions”, in seattle.general‎ (Usenet)

His dick, if I remember correctly, is more of a shower than a grower […]

2003, Austin Foxxe, Three the Hard Way: Tales of Three-way Sex Between Men‎