You have a fungal problem that has infected the soil of the bed If it has gone on for this long probably the whole bed is infected and short of replacing the soil,solarization may be your only option now. Cover the whole bed with black plastic and leave it on all summer. The heat built up under the plastic will kill the fungal spores. Next year you will be able to plant there again. Or you can try one of the fungicides mentioned below.They are taken from a University of Kentucky website I found and saved a long while ago. I tried to find the link but couldn't. I think your problem may be one of these, so I'm giving you both Southern stem blight (fungus) Symptoms: Plants wilt and die in patches in the bed. Small, brown to yellow-brown, spherical sclerotia may be observed clinging to rotted stems at the base of the plant. The sclerotia are often embedded in white fungal mycelium on the stem surface. Control: Remove dead plants and 6 inches of surrounding soil and replace with clean soil or use another kind of plant. In nurseries, PCNB fungicide can be used. Â Botrytis blight (fungus) Symptoms: Dead blotches appear on leaves, flowers, and stems. Stems may rot and plants collapse. Flower buds may fail to open. Diseased flowers decay and fall prematurely. Affected areas may be covered with fuzzy fungal growth and spores. Control: Destroy old plant debris in the fall. Avoid wetting foliage. Prune out nearby shading vegetation. Provide adequate plant spacing. Use fungicides such as chlorothalonil, dicloran, ferbam, iprodione, mancozeb, maneb, thiophanate-methyl, vinclozolin, or mancozeb + thiophanate-methyl. Read the label for lists of specific plants allowed for each fungicide.

I do love scaevola in pots and this year it has been particularly lovely. My favorite combo is with Lemonbird Cosmos. That clear yellow with the blue is terrific. For the second year in a row, I am using Profusion Zinnias, white, with Blue Salvia farinacea Rhea. They are in a half circle bed at my front entryway backed with a thick row of yellow Beautiful Edgings Daylilies. They look perfectly fresh and neat all the time, even in our 100 degrees we are having day after day, and will until frost. Hard to beat. I am using the Profusion Zinnias, Fire, with blue salvias in one of my other beds. The Fire holds its color better than any of the other colored Profusions I have tried. Cameron, if you see this, thanks for the tip on where to get the helioptrope Azure Skies. I got three plants and they are going like gangbusters. I am thrilled!

Gomphrena has been long blooming and wonderful in a vibrant shade of purple. I love the form of this plant. Next year I want to try it in at least several colors (red, purple, pink). The colors are sunfast and beautiful. Scaveola (I think it might be named 'Blue Wonder') has tolerated a great deal of heat and dryness without missing a beat. It is one of my new favorites. Aztec trailing verbena in some shade of plum won't be returning. The flowers are a beautiful color but they bloom infrequently and the foliage is nothing great.

Anything rated Zone 3/4/5 (if you have Zone 6/7 winter) should do okay in a container, provided there is adequate drainage in the container and you can take steps to do some protection in severe cold spells and keep excessive moisture out of the container through winter, which can often kill a plant faster (rotting a crown) than any cold. The phloxes (paniculata/"Summer phlox" or subulata "creeping phlox") are hardy to Zone 4 & 3 respectively The heucheras (depending on type) are hardy to Zones 3/4 Astilbes are generally Zone 4. Daylilies can be Zone 3/4 depending on variety. Many of the mints (a large family) are very hardy and many of the menthas within that family are generally hardy to Zone 3. They can also grow in shade where other herbs prefer more sun. Some of the other plants you mention like the vinca, impatiens, trailing lobelia, pansies, basil are either tender perennials or annuals and may or may not reseed. I have seen the regular impatiens reseed here but not sure about the new guineas. One good reseeder as annual or perennial depending on variety (where some are hardy and others tender) are the salvias (which are in the mint family). They do like a little more light but some of the dwarf varieties might offer a nice combination plus with dead-heading, they can go from all summer until frost knocks them back. Another mint family potential reseeder and/or perennial are the balms (lemon balm, bee balm, etc). Yet another possibility includes one of my staples - the wax begonia and petunias. I have had both reseed as well and with the begonia being a tender perennial, they can be scooped out and nursed inside to be planted out the following season. They like other tender perennials, tend to have a longer bloom duration than the hardies - akin to annuals. The petunias bloom better in more sun but can have a decent bloom in part sun. Don't be afraid to grow perennials. If they spread, just dump them out, divide, and replant! I've done this with my containered daylilies and hostas and will be doing it for my asiatic lilies hopefully this fall (I keep putting it off...lol).