It will not hurt to grow them in pots until you have your Arbor put up...you didn't say what size pots that the clematis came in...if they are baby plants potting up will only help them grow stronger root systems anyway..just plant them about 2-4 inches deeper than the pots they came in with some bonemeal in the planting hole...I would dig a hole in the garden and drop the pots and bring the soil back up around the pots...remember to keep your clematis moist..they like their roots to stay moist...then come time when you are ready to give them a permanent home in your gardens just pull up the pots outta the soil and plant the same way...Jeanne