Dahlia - sprouted indoors - most going crazy- can I put out in unheated GH

in Plants
Hi there- first time growing Dahlias- I have about 12 which I potted up end of March and most have gone crazy- I have pinched back some but growth is prolific- they are on a windowsill - shall I put them into unheated GH to slow down growth a bit, before planting out in June and harden them off ? ( I feel so grown up using these words like I know what they mean !)

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If you do see frost expected then you could cover them with horticultural fleece for the night to keep them safe.