Delphs are heavy feeders. I give them compost every spring. You could also give them a balanced fertilizer. Brown and yellowing leaves is probably caused by not enough nutrients.

They also get powdery mildew if they don't get enough sun and space. They need lots of air circulation. Delph worms are another problem, that you may see. The worms curl the leaves. If you don't removed the worms, they will ruin the flowers. You can just pick off the green worms by hand.

Sierra

I was going to ask if delphs die back like their annual relatives larkspurs do. Mine have, so either I didn't feed them enough and they died, or I have lost them. Just me, I hope you don't mind me asking a related question on your thread.

Sue

Hi Sue, Ummmm my delphs don't die back till they get frosted. However by the end of the season they are starting to pale a bit. But my growing season is very short. I would just wait and see if they come back next year.

Delphs are pretty tough. The summer before this one, while I was away there was a huge wind storm. When I came home my white delph at the front was broken and flattened. I cut it back to the ground.....and it grew and bloomed again by the end of the season. It also came back huge this year.

I also had a fancy lilac that went dormant mid summer last year.....but it came back this year just fine and even flowered. Gardening is a lot of just wait and see....and many times you will be pleasantly surprised.

Sierra

I planted my delphinium in areas of my garden with good air flow next to a wire fence. It's better not to plant them right up against your house wall or a solid fence. The newer varieties are less prone to mildew but mine are old ones so I take the precaution of giving them airspace. I also don't water them later than mid-afternoon altho otherwise I have no rules for watering the rest of the garden, any old time seems to be OK.

I'm sure they will love some good compost also as previously mentioned.