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dying plants, but don't know why

3 years ago

We have been struggling since May to plant a small garden in large containers on our back terrace (Zone 7b). It doesn't get much sun--about 2-6 hours in the summer, and I am coming to realize, no directly sunlight in the winter because the sun is so low.

We looked specifically for shade plants and tried to plant things that would bloom at different times. The Japanese Anemones bloomed well. Other plants repeatedly died and grew back, and bloomed a little (or have not yet been in season so not sure if they would bloom), including some Clematis (about half of them bloomed anemically for a few weeks) that are supposed to survive well in shade, and some Hellebores (other helebores just died and never came back). Some delphiniums that were supposed to be shade tolerant basically just died after being put into the ground, despite careful care--one started to come back in October, but has since died again as well. Other plants seemed to be healthy for several months and then just died completely, quite quickly in a week (Viburnum, Bleeding heart) even though I cannot reconstruct any differences (they did not freeze, were not watered more or less, etc). They trived for months, then suddenly wilted, then a few days later turned brown and hard, and then lost their leaves and disintegrated into the ground. I had been regularly spraying neem oil and sprinkling cinnamon around the roots, because I did see some white and brown spots on some of the plants, but the plants all really seem to be being killed by something and I cannot figure out what it is. They have all been fertilized and watered regularly, and their dying off did not correlate with particularly cold weather (most of them are winter hard anyway). I have tried to follow care directions for each plant type.

I have some bulbs to plant that I should have gotten into the ground last month, but I have been scared to plant them, because I don't want them to just rot in the containers, if there is something wrong with that soil. I've attached some photos--am hoping someone here will have advice?

I would also like to replant some of the stuff that died (viburnum, bleeding heart, the helebores that have not made it so far), but I don't want to just throw good money after bad. I'm also wondering if the delphiniums are just not able to grow here, or if they were killed by something in the soil (or by something that came with them in the soil from the nursery). I love delphiniums, but don't want to replant just to have them die instantly again. I got into this with the assumption that not all of the stuff I tried would thrive in our shady back garden.

I have thought about putting in some LED grow lights, but don't know if that is worth the expense/complication. We just had two trees cut down in the back yard, but here it is very far north so there just isn't that much sun in the fall/winter/spring anyway (and stuff seems to thrive in the wild in the nearby parks just fine).

(I know that the containers are over planted right now, but we will probably only be in this house for 2 years, and then for a while we will only be here in summer, and I predicted that some percentage of what I planted would die, so I'd rather overplant now, and remove later, than sit around for years looking at big patches of dirt with only a few sprigs of stuff growing in them).

Would appreciate any advice! Thanks for reading my post!

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