Hydrangea in containers

[DBCooper]

Hi all, noob here looking for a little input.

Last year, toward the end of the season my local garden center had their Endless Summer hydrangea marked 35% off, and I picked up a few and divided them. I planted them on the west side of my house at the time, but then I changed my mind on the location. A few weeks ago I dug them up, potted them, and brought them in the house. Currently I have them indoors under grow lights on timers; all of them are out of dormancy and looking nice.

I have a bunch of big round plastic tubs (22" dia x 16" tall) that I'm planning on planting them in, so that I can keep them on my back patio on the east side of the house. I figure the containers will allow me to rearrange them whenever I feel like it, and allow me to control the soil pH to produce the blue color I want.

Anyway, I have two questions:
1) What should I use for a soil mixture ? This would take a LOT of potting soil if that's the best way to go. Is it better to make a mix of topsoil or garden soil and spagnum ?

2) When winter time rolls around, the best I'll be able to do is drag the containers up close to the house, and wrap some insulation around them if need be. With about 4 cubic feet of volume each, should those winter okay in zone 6b ?

Bonus: here's a pic of the portion of one of the plants I kept inside all winter. It didn't do much for most of the winter, so I put it in a warm grow tent for a few weeks, and it did this

 

[oneeye]

I love growing plants indoors because they grow so well. I have had better production with plants indoors than outdoors. If it were me, I would use Pro-mix BX or Pro-mix Hp to best maintain an acidic pH needed for Hydrangeas. If you use garden soil the pH will be much higher and minimize flowers and color production. The Pro-mix can be fed liquid Nutrients to keep flower production very high.

Another potting fav is Roots Organic, but it is very expensive. All you add with it, is plain water and never have to feed ever. The pH for Roots Organic is 4.9 to 5.2 pH which is perfect for producing large dark heavy colored flowers.
The zone you're in is not suitable for most hydrangea's, however the "Panicle hydrangea" would grow in 6b and can be grown as low as zone 4.

 

[DBCooper]

Update: After weighing options, I opted to mix my own potting soil from peat moss, topsoil, and manure in equal parts, adding in some 5-5-5 slow release fertilizer and some soil acidifier. Ready-made potting soil was just going to be too expensive for the amount I needed. I ended up making about 400 lbs of potting soil, and used probably 350 lbs on these 7 containers for the hydrangea.

For some reason, the soil pH came out at about 7... so I'm watering with 1 TBS aluminum sulfate per half gallon of water, and re-checking frequently until I get them down to a pH of about 5. I already have experimented with that aluminum sulfate solution when I adjusted the soil pH for the plant in my first pic; so I don't expect any issues.

They were looking pretty happy out on the back patio, a little sunburn adjusting to real sunlight, but not too bad. Aaaaand we have night time temperatures diving down into the 30's, possibly high 20's coming up. So they all got dragged in the house under an LED grow light for a little while longer. Can you guess which of the 7 plants I just dug up from the yard, and which 6 spent a couple weeks in the grow tent ? lol