It may be busy developing a good root system. Water, mulch and fertilize appropriately. It looks fine. Start fertilizing after your average date of last frost and stop fertilizing three months before your average date of first frost. Use a cup of cottonseed meal, organic compost or composted manure. Or use a general, purpose, slow release, chemical fertilizer with a NPK Ratio of about 10-10-10. I assume the soil has no mineral deficiencies. Never water the soil to avoid leaf spots; water the soil instead, as soon as a finger inserted into the soil to a depth of 3-4" feels dry or almost dry. Water deeply with enough water to moisten the soil near 6-8" deep. Maintain 3-4" of organic mulch at all times of the year. I Atlanta, I used to provide either dappled sun or morning sun until 11am or so.

Thank you so much!

I would like to plant another hydrangea in the area, which I grew from a cut. It is now in a pot, bigger than this one. is this good time to plant?

Yes, indeed, now is a good time for the bigger plant. The key is as long as it has developed a good size root system. Otherwise, keep it in a protected area during the first winter. Do not let the soil then get bone dry if winter turns out to be dry. Should there be an extreme winter event, I would cover the plant with mulch to winter protect it. Remove the protection when it breaks dormancy; then only mulch and water. Be prepared to protect from late frosts until your average date of last frost... In Atlanta, that fell around the 2nd-3rd weeks of April. Afterwards, you can start to fertilize, about once every three months with a slow release fertilizer like the ones mentioned previously.

Most frown upon chemical fertilizers, but in situations like this, a few good doses of high nitrogen miracle grow can help to kick start growth. Might be too late in the year this year, but next spring if it's still stunted, I would give a good dosing of MG every week.

@charles kidder,

Thank you for cofirming - I am certainly planning for some extra fertilizer regimen next spring.

In the meantime, I dug it up (easy to do since it is so small) and replanted it in a deeper hole filled with nice fluffy manure and soil conditioner. I have GA clay and given how small it was, I may have scrimped on the hole when I planted it.

It looks fine and green, just not growing. Hopefully, it will take off next season. If MG is what it takes, that's what it will be.

Thank you all!