"Brian" wrote in message
...
C.cheiri is technically a perennial but is so short lived that it is used
as
a biennial.
They will flower now but are then of little or no use and are thrown
away.They are replaced in the autumn from seedlings sown and grown this
summer.
You might be able to keep them alive but they will never flower so well
again, even if they survive.
There is one variety~Harpur Crewe~that is only propagated by cuttings.
Best Wishes.

On the west coast, wallflowers may be longer lived than elsewhere. There is
a stunning planting of mixed wallflowers just up the street from me that is
at least five years old and I have many in my garden that are 3 or 4 years
old. I cut them back hard after bloom - this keeps the plants relatively
compact and may even encourage a late rebloom. They also reseed rather
freely if you are not prompt about deadheading. Summer dryness and low
humidity may be the key to longevity.

pam - gardengal