Question
I have several patches of annual vincas planted in my garden.  In two of the groupings (which receive approx 8 hours sun starting in a.m.), the leaves have become yellow on some of the plants, but not all of them.  It seems somewhat random since one plant might look green, bushy and thriving, while the few surrounding it have yellowing leaves (starting with the larger leaves) and are not thriving.  All the vinca in the third garden patch are thriving (this area gets about the same amount of sun, but more in the afternoon).  I dug up a couple of the plants and the soil seems moist but not wet.  Any ideas?

Answer
Hi Pam,
Is the soil draining well?  If it remains consistently damp, this could cause the yellowing.  Usually, yellow leaves means too much water or too much fertilizer.  So, if you're feeding them too, you might want to hold off on that too.  It sounds like they're getting enough sunlight so perhaps they are too damp.  Have you had a lot of rain lately?  Sometimes, this will happen if there has been an overabundance of rain.  I hope this helps.
Tom