13,520 Garden Web Discussions | Perennials
Nope - that's not powdery mildew. It seems the culprit has been identified in your other post as sawfly larvae.
Powdery mildew is very heavily influenced by climatic conditions but not necessarily rain. In fact, rain or irrigation water generally destroys the spores that lead to PM. It is most often encouraged by warm, high humidity conditions and dry soils, which explains why it typically shows up late season when these conditions are most prevalent.
new posts are always good ... its about your plant.. in your area .. etc ...
unless they clearly IDd the problem ... in which case.. you already got your answer ...
you cant kill LOV ... i wouldnt worry about it ... there is always next.. not every year is a great one.. the farmers lament .. lol ...
removal of competition wouldnt hurt ...
ken
peren.all - yeah, the mosquitoes are out in force and hungry here too! Yesterday I did a quick foray down near the 'wet corner' to whack off fading goatsbead flowers/developing seeds. I didn't put on my bug shirt - and was immediately under attack! I did a very rough job, and was out of there within a minute! There is still one more goatsbead to deadhead - DH will do it as the mosquitoes are less fond of his blood :-) I'm also useless in the heat so, while there is deadheading etc. needed in the front garden, it's going to have to wait until mid-week when it's supposed to be cooler again.
ruth and rouge - the Niobe and regal lily combination is a 'happy accident'. The lilies were planted maybe 8-10 years ago. The cursed lily beetles do less damage to the regal lilies than to other lilies, in my experience (the regal lily foliage is very narrow and somewhat coarse-textured; I think the beetles may consider it a poorer food source for the larvae perhaps.) But the lilies gradually faded away (too dry/too heavy soil maybe....?). The Niobe (and Henryi) clematises that grows on the arbour wilted badly early last summer so I wasn't expecting much from them this year. I thought dryness might be an issue, so asked DH to water the base of the arbour whenever he was watering his veggie pots nearby. Bingo! Great looking Niobe this year, and the lily on the right ride of the arbour returned from the dead! :-)
Thyme - I thought you'd like to see the heptacodium :-) I just checked my records - I planted it in 2002. I couldn't find a tree-form one so bought a small shrub one that only had 3 stems. I cut off the two smallest stems and let the other one become the tree trunk. It has certainly now surpassed the size I expected it to get - but we love it! (and so do the bees, butterflies and hummingbirds when it blooms!) The past two nasty winters didn't bother it a bit, so it's obviously very hardy. It doesn't have much in the way of fall color, and it gets too cold too early here to have the pink show from the calyxes make a show after the flowers finish in areas further south. But it's definitely worth growing! I can't imagine how much space it would be taking up though if I had left it as a shrub! Tree-form is certainly the way to go unless you have a huge space for it....
Thank you everyone for your answers! To Ken bits of it are green and fresh, but the plant in whole doesn't look healthy and it has hardly grown since I planted it in April. I compared that Lavender with the other one I brought because when I brought both of them it was the one pictured that was actually bigger and now it's the total opposite and the other one has bloomed and grown out compared to this one.
Where it's planted it is quite rocky compared to where the other one is so maybe that could be a problem? It has never really grew properly tbh since I planted it in April and gave it a pruning to encourage new growth. It gets sun quite a bit and I even cut down some bushes which it was near so it can get more sunlight, so I don't think it could be the sun. I never really watered it obsessively, but I started watering a bit more when I noticed it wasn't really growing and recently when it has been really hot. 
I took better pics now so everyone can see it better. It looks worse than before because next doors children were playing around the garden and damaged it.
I have been wintersowing Jacob's Ladder every year for 4-5 years and get spotty germination. The plants don't seem to thrive anywhere, but do best with bright shade or mottled shade and good drainage. The blooms are nice and at a time when not much else is blooming. I'm going to try to scatter as many as I can throughout my shady yard and see if at least a few can find a happy spot.
Martha
This is what part of my knock-out roses looked like a week ago (I cut out all of the dead stuff) and it has spread to an unidentified yellow-flowering spring perennial that is in front of the roses. I thought it is powdery mildew, as a result of our really wet late spring. This didn't happen to any of the same plants last year.
I've got a NOID lavender that I've had for over 10 years, comes back beautifully every year. All I do is trim it back to almost ground level in spring. Agree with above that it's the soil and sharp drainage that matters. I don't think it has to do with the humidity. I planted some lavender as "fillers" in a bed that has heavier soil and tends to hold moisture well and not one of them made it through the first winter.
I grew up in a home on land with several mature and juvenile hemlocks, and you need to be very, very careful of their root systems. If you plant lawn over their roots, or regularly use a riding lawn mower over their roots, you'll start to see the trees decline. My father lost several before getting good tree expert advice that helped save the rest: Mulch, don't plant, over their root zone.
He circled the area in an attractive way, put in large bark mulch, and in a spot here and there put in large rocks, or a clump of lilies, or a large specimen hosta. There were small bunches of spreading Lamium, too, but not much. On the whole, if you want the hemlock to thrive, you need to leave it alone. They are very, very sensitive to root compaction and competition. Also, they love coolness and moisture and need regular watering if they don't have their normal cool, damp forested habitat around them.
They're beautiful trees. Enjoy yours.
THE plant for dry shade--Geranium macrorrhizum--big Root Geranium. Semi evergreen, handsome groundcover, highly deer resistant, easy to control, very attractive with late spring bloom and no dead heading, dividing or other attention required. What more could you want? Alternate--Epimedium sulphureum--slower to fill in, must be cut back in late winter, but very attractive and has early bloom.
If you garden in deer country, as I do, there is very little point in planting plants that deer love. It's a losing battle. And while it is true that starving deer will eat anything, there is a huge range of plants for both sun and shade that they generally have very little interest in. If your yard has mostly unappealing plants, they won't hang out there much. That said, I ALWAYS spray a new plant with a good repellant so if some young thing tries it, their first experience is YUCK! They spread the word. And having said all that, yes, I do have a few plants that deer will eat, and I do spray those. But they are very few, so keeping up with the spraying is not onerous and doesn't break the bank. However, I have NO hostas, yews, or tulips--the ones that say "Free Lunch".
Another comparison of Silver & Sea Hearts, though the photos aren't as clear:
You might also want to check out Callirhoe digitata--a tall, very open and airy plant with gray/green stems and deep fuschia flowers scattered up and down the stems that look as if they're floating in air. The plant has a tiny footprint, is very see-through, and knocks out everyone who sees it. It seeds about very restrainedly, and can be easily transplanted when small. You'll love it.
I planted under my two maples before any one told me it was difficult/impossible to do so. I have not found it that difficult. I do water weekly or even twice weekly during a drought, which we do not get often. I also mulch yearly in late Spring and spread compost. This is very bright shade though since trees face South. There is no direct sunlight though except for the Southern edge of this bed where you see the rudbeckia. I also have a clump of rudbeckia in total shade and they do well there too. This picture is from September of 2014 and the beds were installed in 2006. Plants are most of the ones mentioned already, epimedium, hosta, grasses, turtlehead, anemones, rudbeckia, ferns, geraniums, lungwort, ligularia, yellow waxbells, solomon's seal.
Looks beautiful.
(Not all varieties of maples are water sucking monsters ;)).