Perennial Plant Out ?

Bought a few perennial plugs this year . All planted on into small pots and doing very well in the GH . When would it be OK to plant them out into the garden ?
Aquilegia
Penstemon
Helianathemum
Salvia Nemorosa

TIA

 

they are all hardy HarryS but I would wait until they fill those pots. Personally, I pot them on again into half litre or 1 litre pots before planting them out. Wont be long at this time of year before they reach 1 litre size.

 

Dont forget to harden off.
Which I would be doing now.

 

Thanks @pete , @Verdun . I'll start potting them up into larger pots today . I made myself a cold frame over winter . This will be great for hardening off , I can leave lid open during the day and close at night .