I went to the Jungle Growth website and, although there was an alluring "Which Jungle Growth product is best for you?" display, not one
of the links worked!
So I still
don't know what the ingredients of any of the planting mixes they offer are. But I will say that a plant which is displaying signs of inadequate watering, despite attentive care, may be sitting in a mix with too much peat moss
. Peat is hydrophobic; that is, it resists getting wet.
I know that a 24-inch pot (esp. if it's terra cotta) is going to be very heavy....and it may also be on the big side for an immediate step-up pot for this hydrangea (another possible challenge for the plant; feel free to plant it in a smaller pot if the plant will fit comfortably).
In any case, one way to proceed is to submerge the container in a large sink or bathtub of warm--not hot--water. The water should come just to the soil line but not come over the edge of the pot.
The idea is that the potting medium/soil will absorb water from the bottom up. Leave the container in the water until bubbles stop rising; this may take 15 to 20 minutes, depending on the volume and dryness of the planting medium. Then, when the planting medium is fully wetted, let the water drain out of the sink/tub. Leave the container in the sink/tub for now.
After an hour (approx.) of draining, the container can be returned to its usual location. The peat, now wet, will not be so resistant to watering, and a regular schedule can be observed. *whew*
I have cymbidiums, BTW, and grew 12-foot-tall hollyhocks when we lived in Berkeley. Now we live a whole 6 miles north (wow...) of our previous house, and I haven't been able (in three years of trying) to get hollyhocks higher than 5 feet.
So "If you can grow orchids, you can grow anything"...I wish!
Sunset Zone 17, USDA Zone 9