If you observe signs of chlorosis (the leaves turn light green or yellow but the leaf veins remain dark green), you need to acidify the soil. However, I did not see much of that in the pictures.
I too suspect that the plant was winter protected, did not getting much sun and is not producing much chlorophyll (the green stuff) yet. You can bring it outside in stages so it will acclimate. For example, take it outside into full but bright shade for a few days (so no direct sunlight). Then let it get two hours of very early morning sun only for a few days. Then a few more hours of sun. Then make sure it starts to get shade by 11am-ish. No afternoon or evening sun now or during the summer months. Plant it where it gets shade by 11am, is not too windy and where water does not collect in the area after heavy rains...
Lack of sun due to winter protection can also produce stems that are also white instead of light green. But after photosynthesis begins, the white parts will turn green. Not fast, mind you, slowly. Once the plant parts look a normal green while in full but bright shade, you can start to acclimate it to sunlight; then plant it in the ground or in a pot.
The dried out stems can be cut all the way down if they do not leaf out by the end of May or start of June. You can also carefully do a scratch test at those times to see if you see green. The leaves look like they belong to either a hydrangea serrata or hydrangea macrophylla (aka, mophead or lacecap) but they are still too small to tell which one. Maintain the soil as evenly moist as you can for now and thru summer. Do not fertilize yet. Wait until two weeks after your average date of last frost to fertilize. Protect it from late frosts with a frost cloth (or bring it temporarily into the garage or inside) to protect the leaves from getting zapped by frost). Water deeply the night before a late frost.