Hi. I also needed to shade my hydrangeas starting at noon when the sun is very hot. What I did is, I bought 14 green plastic rod stakes and inserted them in the ground first using a hammer. Then I bought a roll of burlap and cut it to make a long 10 ft canopy to cover them above the tops of the leaves. They must not touch! I decided to double the canopy with another piece to give more shade but it is diffused sunlight which is perfect for them. Hydrangeas are smart. They tell you what they love and when to protect them. Since I have done this, they have thanked me and are so incredibly lush and have now over 50 plus buds! I don't worry about the sides too much but I cover all four of my hydrangeas making another canopy for the back side as well that stick out in the sun too. I leave it on for 21/2 hours only and then remove it carefully since by 2:30 they are jn the shade naturally. I found that to use twist ties are a pain to secure the burlap to the rod stakes and buying shade cloth clips are expensive too so I saved money and purchased med sized plastic claw hair clips and they r perfect!!!! They hug the burlap and the rod. If I know I will be out for the day, I would cover them up before I leave because they will get filtered light but won't burn and that is most important! Also when they do bloom, the burlap canopy will preserve the blue hydrangea mop heads much longer and won't fade from the scorching sun on those hot days. It works! I give them morning sun from the time the sun comes up till noon. That is what they love and need! I love blue hydrangeas with a passion.

I kept some of the old wood too but have some leafing out on the bottom half of some of them. I kept some of the old wood to help the blooms to give additional support when they bloom. They get heavy! I will snip off some of the tops of the old wood that did not leaf out but not to the bottom as there is leafing! I have used aluminum sulfate diluted in water every 10 to 14 days. Works fine. I have fertilized a little only. I have applied granules too of aluminum s. but prefer drenching it. I use a soaker hose too at times to water and just use the hose too. I use Neem oil as a preventative to keep any possible future bugs from wanting to come. It works. The shade cover is the answer to all my prayers though and with all of these types of care, I now have over 50 buds. I winterize then here in NY as winters here are brutal. When winter comes again I will use the stake rods in a circle around each plant and double cover the plant with burlap tying the branches up first with twine and then covering them completely. I will try also something new this time as well. I will purchase at Home Depot, Styrofoam, and will cut it into a circle and place it on the top and cover all with burlap. When it was zero here some of my buds formed beautifully in the winter but didn't survive with one layer of burlap so that is why I will double the burlap and use Styrofoam to keep the tops more insulated. I want all the winter buds to survive! They are my babies! Lol ♡

Shade cloth should be available at any local greenhouse or landscape supply company. Even some retail nurseries carry it. If nothing local (no greenhouses in your area?) you can order it online. Look for 30% shade cloth - it should do the trick. This is very lightweight fabric and is easily draped or affixed to uprights to provide the shelter and sun protection you need.
shade cloth