If you don't (or can't) flush the soil regularly when you water, the build-up of solubles (salts) in the soil is assured. As the level of salt in the soil increases, it becomes increasingly difficult for the plant to take up water and nutrients. High salt levels are also toxic to roots. In addition, the reduced rootage, and transpiring surface area above ground means less water usage and increased danger of over-watering. The easiest fix for problems like this it to prevent it from occurring in the first place by using a soil that will allow you to water correctly, virtually making over-watering and solubles build-up both non-issues. I think if you make that your goal, you can make some pretty big strides forward in your ability to keep your plants happy. For now, Here is what I would suggest you do: Move the tree to where you can flush the pot thoroughly - in the tub or shower is great. Saturate the soil with room temperature water and wait 10 minutes. Then, flush the soil with a volume of water at least equal to the volume of the container it's in .... 5-10 times - the more the better. This helps remove accumulating solubles (salt build-up) from the soil. After it stops draining, remove the tree from the pot & set it on newspaper over night. The paper will 'pull' excess water from the soil. Return it to the same pot next day. Wait to water until a wood dowel stuck deep into the soil comes out clean & dry. When it needs it's first watering after the flush, fertilize with a 1/2 recommended strength of MG 24-8-16 or 12-4-8, or Foliage-Pro 9-3-6 (my favorite). I suggest you add a wick to the pot for now. The wick will help excess water drain & allow you to water properly. You'll need to arrange for the pot to be ABOVE a collection saucer when you water, with the wick dangling below the bot 2-3", but NOT touching the effluent that collects in the saucer. When you water - use enough water so at least 10-15% of the total volume of water you apply exits the drain or drips off the wick. This keeps solubles from accumulating in the soil. You can learn more about why how water behaves in container soils here. If you absorb the information in this thread, it will stay with you and help you with your container gardening from now on. Any questions you have before you flush the soil and fertilize are welcome. Do you understand how the wick will help you? If you're still interested - I'll help you get set up so you can water properly until you can repot. Repotting is different from potting up, in that repotting includes bare-rooting, a soil change, and root pruning. Take care. Al

It is a powdery mildew infestation. Common in hydrangeas. I have even seen some at plant nurseries when they pack the pots closely to take less time when watering. To get rid of the fungus, make life miserable to the fungal spores by following some clean housekeeping guidelines: do not overhead water the shrub; instead, water the soil early in the mornings; throw away the spent flowers and leaves into the trash; discard plant debris under the shrub; replace the mulch with new mulch if the infestation is heavy; do not overwater as this increases the humidity in the environment and the spores will love you for that; separate plants to improve the air flow between them; consider fungicides if this problems occurs early (as it is doing now) and has spread a lot. First fungicide to try is milk: spray weekly during the day using 1 part milk to 9 parts water or slightly more concentrated. Because it works more to prevent PM, I sometimes use 4 teaspoons of baking soda, 2 tablespoons of horticultural oil and 1 gallon of water instead. If you decide to apply chemical fungicides, be aware that some can cost $$. Apply them on the top/bottom of the leaves per label directions. Consider reapplying next year before the time that this issue started (early May?). Fungicides Cleared for the Control of Powdery Mildew on Hydrangea: azoxystrobin (Heritage; has the smallest application rate and largest repeat interval); fenarimol (Rubigan); fenarimol (Cleary's 3336). You can also use Sunspray Ultrafine Oil. Luis

With the intensity of a midwest summer, I'd say a full sun location for this plant is just a bit too severe. The brown leaves are sunburn/scorch. It is a woodland plant in its native habitat and a full sun exposure without copious amounts of water is expecting a bit much of it. It is best sited on an eastern or northern exposure in rich, well-draining but moisture retentive soil. Unless located in very heavy shade, you can expect reliable blooming once it is well enough established, which can take a number of years. Personally, I'd relocate it to a shadier location (morning sun, afternoon shade preferred) or provide some sort of protection until your shade fills in.

Generally speaking, you're NOT supposed to use weed killer in the same beds as good plants, because rain or watering can start washing it into the soil/roots around the good plants, and sicken or kill them from the ground up. I'd stick to hand-weeding and mulch for weed control IN beds. Or you can get some kind of slow-release fertilizer / weed controller pellets and apply that early in the season. Or at least consider gravity. If you water downhill from good plants you should be relatively okay. But if your plants are on the same level or downhill from the weed killer, there will be problems. Otherwise, your pictures indicate regular heat/sun stress behavior. This is normal, unless you water a little in the evening and the plant still looks like that first thing the next day.