I had a similar situation, and the consensus here for my case was it was likely planted too deep.

It might also be root competition from your Japanese Maple. My Bloodgood JM got so large that none of the hostas underneath it survived.

dig them up.. clean out all the maple roots ... and replant them ...

july is root growing time to store energy to come up next spring ... so its the perfect time to do it ...

a pic will confirm if im on the right track ...

how do you water them .. if you rely on sprinklers.. are you sure they are getting hit with the water???

one way or the other.. they are in drought ...

take pix if you find anything in the roots out of the ordinary ....

btw: zone is simply the coldest predicted day in winter.. it tells us nothing else .. and z8 can span from pnw.. to arizona.. to the carolinas... florida.. etc .. and some of those place you just shouldnt be bothering with hosts.. so plz give us a big city name ... what if these 2 are the norm.. and the better ones are the exception ... eh??

ken

ps: i hope you arent fert'g the maple .. and never fert anything under the maple.. or the maple will grow into the roots of the other plants.. to steal the fert ...

I live in Tacoma, WA.

I never thought about root competition with my Japanese Maple. Not sure why these two would have issues, but the others under it don't. I can see about digging them up and checking their roots.

As for watering, there is a sprinkler system, but I also hand water at times. I also fertilize the bed they're in with an organic spray fertilizer (fish/seaweed), but I don't fertilize the Japanese Maple.

a tree can have a root mass twice as big as the tree you see above ground.. mostly in a pancake shape ... and with JMs it rather fibrous ... a dense mat ... sucking the life out of anything planted under them ....

if you are feeding ANYTHING around the tree ... the tree is growing its roots to the fert ...

frankly.. i NEVER fert trees .. and rarely fert my garden at all .. they are plants.. not children ... and i love my trees... but i also want to play in the soil under them.. so i dont want them to be anymore root aggressive than they already are ...

sounds like great water method.. so it just has to be the tree roots ...

it could be planted too deep as suggested.. but i would think if you planted 4.. you would have made the same mistake 4 times .. of sourse.. the seller could have potted them poorly and you didnt check ...

anyway... the pips or where the leaf stalk hits the crown ... ... should be at soil level .. you should be able to see this in spring .. and the crown just at soil level ...

with your location.. im more surprised you arent complaining about voracious slugs .. lol ...

ken

As Ken said, check that your sprinkler system is actually getting water to those two hosta---especially since you said that the two hosta doing poorly are getting more sun than the two that are doing well. It may be that two hosta that are growing well are blocking water going to the other two? My neighbor has planted a hosta in his lovely front garden that doesn't get any water from their sprinkler. I can tell because it is right beside my property and I can see dry soil around very wet soil. I suspect that my neighbors use their sprinkler for a good period of time---enough maybe to saturate this hosta inground as it is doing very well so far.

And yes, do dig the two hosta out of the ground. That will give you a chance to amend the soil and reposition. Good luck!

If you value the Japanese maple at all, do NOT dig around and mess with the hostas. Hostas are a dime a dozen compared to a JM and the root damage you can do can be nonrecoverable and fatal....especially at this time of year. JM's do NOT have aggressive root systems at all and they don't "suck the life out of anything"!! In fact, they are very delicate and sensitive to any disturbance in the area.

weve been thru this before gal ....

she dug a hole.. to plant the hosta.. not very long ago ... the tree apparently didnt care ....

i highly doubt redigging the hole to clean it out or to move the hosta is going to hurt the tree any further ...

that said.. i would NOT run a rototiller under it ..

and i wouldnt be planning on planting much of anything there in the future ... if not just to not harm the tree ... but for the reason this hosta is failing ... the JM is an aggressive rooted plant that will steal all available water.. given the chance ...

ken

ps: funny aside ... i had a ornamental purple plum in the front of the picture winter.. until it got black knot .... so i removed it.. and replaced it with the generic seed grown bloodgood to keep the maroon leaf color in the picture window .... and after a few years.. unlike the plum.. i could not plant anything under the bloodgood.. because nothing would thrive .... mostly because of the dense fibrous root mat.. and i wasnt walking out there every day to water anything to achieve such ... i really dont know what was funny about it.. looking back.. lol ...

My Japanese maple has Virginia creeper growing all around its base. I keep it trimmed so it doesn't climb up the maple. The Va, Creeper creeped over from where it's mainly growing. The JP maple is extremely healthy and so is the Va. creeper. No deep roots on the creeper. JP took off the spring after I applied HappyFrog JP Maple fertilizer in the fall.

Virginia creeper might be fine in Michigan, but here in Alabama it is horribly invasive, both through its viney growth and profuse seedlings.

It really took me aback to see it grown as an ornamental in Colorado.

I have a Japanese Maple which has lots of fibrous roots under it. I have tons of spiderwort in my yard--they seem to multiply each day! They thrive under the JM other plants do not do as well and most die. I put containers under the JM--filled with lots of coleus and impatiens and hand water them. I totally agree with Ken, the dense roots choke out just about everything--except spiderworts!

Ben D It does act invasive here but I just trim it back. In my backyard it's shady so that slows it down. I like the way its leaves grow to a huge size when it's in shade to increase surface area for photosynthesis.

It was planted at my house when I acquired it. It grows on all four sides of the house. Somehow it's a plant I like very much because it's so attractive including it's navy blue berries and the leaves turn bright red in the fall. It's not invasive enough to bother me except by my favorite magenta lilac where it entwines its tendrils all around requiring me to carefully snip each one to free the lilac. Then I just pull it down.

I wouldn't mess with the hostas right now. We (PNW) are in a serious drought and just came thru a horrendous heat event. Many plants didn't survive and we won't know about the trees for awhile. I'm giving my trees all of the love and attention I can and keeping my fingers crossed that they all survive.

BTW, I have a bunch of hostas growing under a paperbark maple and some of them thrive and others are wimpy. They all receive similar treatment so who knows?

Miles, my spiderwort has been declining and I've been blaming it on competition from perennial geranium. Maybe that's not the problem.

My neighbor has a bunch of spiderwort that's doing well. I think I'll move mine next spring to see if it's happier somewhere else.

I appreciate everyone's input and tips. I think for now I'm going to hand water more to see if that helps the two stunted hostas. There's been a lot of talk about plants not able to grow under a JM, besides my two hostas that have come up small the last few years, I've had quite a bit of success. I have two Wedding Gown Hydrangeas, Rozanne Geraniums, Blue Star Creeper (who has stayed in check in this bed), and of course my Patriot Hostas (you can see here the size comparison of the two on the left compared to the two on the right).

Ben, when it's cooler, maybe I can ship you some. Mine self seeds everywhere in the yard. It's almost invasive. When it gets hot, it tends to bloom less or not al all until it gets cooler towards fall. This year I had lots of blooms in the early spring and then when the temps were in the 90's here it stopped blooming, not growing but just blooming. We will be in the 90s's here again this week so I don't get a lot of blooms right now. What color does your neighbor have? Mine are shades of purple. I have a few white and magenta colored plants but they aren't as vigorous as the purple.

It looks like there is a little slope involved under your JM. The one on the right looks like the water may stay longer penetrating deeper while the one on the left it runs off more quickly. Also, different amounts of sunlight could be affecting them too. And sometimes you just get a runt that doesn't grow as well.