Can they grow in hot weather

Seed cane started anywhere at any time. What is important is that you provide the proper conditions that the seed needs in order to germinate: after cold stratification they want moisture and heat. You dont mention your location, or what kind of hot weather you experience. Japanese BlackPine is a pretty widely adapted tree: Sunset Zones 3 - 12 and 14 - 21. Zones can also be cheated if landscape planted with protection in mind. Think in terms of micro climates when evaluating the landscape.

What else would I need to buy to care for this

The seed germination kit contains everything that you need to start a tree from seed. Once you have achieved germination, and have a new sprout, you will want a small container to transplant into.

how many seeds in the box?

The quantity of seed is based upon the rate of germination that we are achieving in our nursery...we use the very same seed to grow all of our tree seedlings. Enough seed is provided in an attempt to guarantee, with care and conditions, that at least one seed will germinate for you. Depending on tree species, 3-5 seed are included. If you have any issue with germination we will provide replacement seed...all you have to do is drop us a note at customerservice@jonsteen.com

My seeds have been in the refrigerator for 21 days now. But I misplaced the instructions. Can someone post a photo of theirs to tell me what steps to

I did not have success with my seeds as I did not follow instructions properly for numerous reasons but thinking instructions i would think are most likely on Google somewhere and it's been quite awhile since I tried growing mine