Hi there

if the JA keep croaking 3 years in a row, that seems to point to a existing problem with the site conditions.

How much sun, what kind of soil (sand/ loam) how much water...?)

Around here (about southern Germany) the JA are a cherished "exotic vegi" for organic gardeners, they are almost indestructable, get mildewy at the end of the season and spread like hell.

So....

no, I would not spray them.

If you want to grow them mainly for their flowers, there are for sure other Helianthus species that are more reliable and beautiful.

I personally would rather shovel prune the JA and perhaps go for Helianthus microcephalus. There is a light yellow cultivar "Lemon Queen", mine are still flowering right now (z7)

Hopefully someone else chimes in and could recommend other Helianthus, I am not very familiar with the wide range of your (native) species.

They sometimes just don't. Helianthus tuberosus needs a long, hot summer...not the usual cool, damp excuse we see in the UK - at least 2 out of 3 years there will be no flowers on the allotment artichokes (although this year is a flowery one).

We just had a long, hot summer and my JA's look horrible and all the other sunflowers are early. Maybe I will just pull them in spring and find another late-season bloomer.

Mine have never flowered in over 20 years. I grow them as a vegetable so it doesn’t bother me. They’re in heavy clay which never dries out. If you want flowers I think you can do a lot better as suggested above.

That is funny, I would never have thought it could refuse to bloom. I had it for a number of years, and it flowered faithfully. I got rid of it because it was too aggressive for my small garden. The friend who gave it to me let it rampage to its heart’s content over several square yards. It was just a boring green area for most of the year, but when it bloomed, he sat on his high deck, looking out like a king over his own private sea of gold ;-). Both his and my garden have alkaline clay soil.

But yes, if it does not work out for you, just find another tall sunflower.

Yes, it is stunning when it blooms in mass late in the season. How ironic that my JA's decided to bloom this year, although most were affected with mildew which totally collapses the plants. Not the showy bloom I wanted that I see in other yards or along the roadsides.I think I will pull them and replace with another reliable perennial next year. On the good note...they do pull out very easily.

I planted the Jerusalem Artichokes for the first time this Spring. They never grew to more than knee high since the deer kept eating them. The Flowers in your last picture look a bit like my swamp sunflowers, but the leaves on mine are narrower. Mine are just about to start flowering. They are very aggressive spreader, but beautiful when they flower. A lot taller than the label on the tag at the native plant sale suggested....

I came here looking for an answer and would deduct it must be the soil. I have a bed of them that flowers every summer, religiously. I dug some for my father to transplant onto his 150 acre farm for the birds, deer, etc. In 4 years he has never had a single bloom !

I planted them this year for the first time and have huge plants growing but no flowers. I was wondering if they were a weed that grew instead (esp since I’m not good at labeling my plantings), but didn’t want to give up just yet. I will wait the full season through, but now I know they may never flower.

I'm wayyyy up north and Jerusalem artichokes had flowered for me, they were planted at the end of the veggie garden surrounded by forest.

ah ha, from the answers here I believe I understand, my JAs bloomed beautiful late summer for two years but the soil was not fertile enough for other vegetables so we added some natural fertilizers and now two years no blooms. So, it sounds like they are more acid or clay lovers and not good fertile garden soil. Guess will try moving them back

near the woodland. I want them for both root vegetable and late happy yellow flowers.

Actually, I just came back from a vacation to unexpectedly find my very tall Jerusalum Artichokes just covered in golden yellow flowers! It

is September, so flowered late but are very nice, especially as flowering of most other plants have died down. So, adding the natural compost mix was okay. These are planted in full sun on a slight slope, so have good drainage, maybe that is the key factor 🤷🏼‍♀️

I would say drainage is certainly a likely condition for flowers. All those with rich, fertile soil, nutrient holding clay, are not likely to ever see flowers...whereas on my absolute rubbish, sandy, stony, played out soil, JA'a are much more likely to produce a flower. Same with nasturtiums. On lush loamy soil, you may struggle to see a bloom peeping over the jungle of leaves...but on dry old rubbish, they are a delight, competing with the second flush of california poppies for orange-y brilliance.