touchofsky said:I sometimes see that with a few of my daylilies in spring before the soil warms up. I usually give them a watering with a water soluble fertilizer, containing iron. I don't know if it is necessary, but I figure it can't hurt!
Iron sounds like a fantastic idea if it is chlorosis. I add iron to my roses when those leaves get chlorosis. Worked wonders for that species.
There is a good fertilizer out there for petunias and/or vincas which really need a lot of iron to thrive. Pricey though. Buying ferrous sulfate powder is much cheaper (not sure on efficacy, however).
A note to add: Sooby was right. It seems like a pH issue. Ferrous sulfate is supposed to transiently acidify your soil (not unlike the aluminium sulfate that people add to hydrangeas, but is far less toxic than aluminium sulfate which for example would kill an azalea or rhododendron, but the ferrous sulfate would not).