Expert: C.L. Fornari - 8/1/2008

Question
QUESTION: I have 2 containers of petunias....they have been beautiful all summer and now the leave and stems are turning from a dark green to a light green almost white.
they are looking kind of spindly also.  I deadhead all the time and water almost daily because of the sun and heat.  I have given them iron and a water soluble fertilizer....any ideas?

ANSWER: V,
My guess is that the roots of these plants are now down in the bottom of the containers where there are "drainage rocks" or some other non-soil material perhaps?  When plants are in a container they send their roots to the bottom of the container - if there isn't soil at the bottom the roots can't take in nutrients and water and the foliage turns white and plants get spindly because the roots are down where there is basically nothing for them to absorb.

If this is NOT the case - if you have soil all the way to the bottom of the containers, please respond as such and we'll brainstorm from there.

C.L.

---------- FOLLOW-UP ----------

QUESTION: These very big containers with lots of soil so I don't think that is the case. Any other ideas?

Answer
OK - here are some of the other possible causes for foliage turning pale almost white:

1. If the pH of the soil is wildly off - too acid or sweet - plants can't absorb the nutrients that are there. If you used new potting soil this is most likely not the case unless a great deal of lime or something acidic got dumped into the pots. If you used dirt from the ground it's possible that it is very acid or alkaline for some reason.

2. Something else got dumped in the pots that is making the fertilizer completely unavailable. (Have a party recently? I've heard of people dumping drinks into plants or even, heaven forbid, peeing into pots.)

3. Leaves turn pale yellow when the soil is kept too wet - plants can't absorb nutrients if their roots are rotting. Stick your finger in the soil or dig with a spoon to see if it's really moist - smell the pots: they should smell clean and fresh. If they smell a bit "swampy" then you might have root-rot going on.

4. Powdery mildew causes foliage to turn light and the plants to get spindly - if the leaves look like they have very fine, whitish powder on them, it's mildew. This condition happens in moist weather (humid but not much rain) and weakens or even kills plants. You could spray with a product such as Green Cure but if the plants have a bad case of mildew there isn't much you can do to totally reverse the problem. Toss mildewed foliage in the garbage not in your compost pile.

5. You mention the sun so I'm assuming that these containers are in full sun - if they are on a porch where no direct sun hits them than that is the problem.

I hope one of these seems to "fit" and helps you to find the reason your plants aren't doing well!
C.L.