Amazon seller has it titled as::"10 Hybrid Willow Tree Plant - Austree Cuttings Grow 12 Foot 1st Season"Informs me to leave in dark place for up to 3 weeks

I've kept her in my bedroom and the glass jar inside a coke box to block the water and roots from sunlight. But, I'm wondering whats causing her to turn yellow and having the lower leaves die off. Should I plant her asap or feed her some nutrients?

Amazon link if you'd like::

https://www.amazon.com/gp/product/B092556N17/ref=ppx\_yo\_dt\_b\_search\_asin\_title?ie=UTF8&psc=1