I have tried many times to grow asters but they alway die just as they are starting to flower or sooner. Here's an entry from my journal for 2004:
August 26: The plants did not grow very much, but they put out a nice display of flowers. Now, unfortunately, they have mostly succumbed to whatever kills asters in my garden. Most plants have dried up and died. August 29: I pulled the plants out. They were quite dried up, and I saw that their roots systems had not developed since they were planted, but may in fact have diminished.
I subsequently had the plants looked at at the Univ. of Manitoba and they were diagnosed by microscope as having fusarium.
December 2: They were almost certainly killed by fusarium fungus. This fungus resides in the soil and enters the plant through the roots. It then spreads upwards into the whole plant, killing it. It is quite specific, affecting (probably) only asters, and then not every variety.
I understand that fusarium is supposed to die out if no suitable host plants are available. I have waited years between tries, and the asters die next try. I have tried several varieties of aster, with the same result. I have tried different end of the garden. No luck. There are no plants nearby that I recognize as disease vectors. Asters in pots do fine until I put them in the ground. Asters in the city parks grow fine, and the city does not use any preventative chemicals.
How can I grow asters in my garden?