Question
I live in Middletown, CT.  I have been planting purple wave petunias in the front of my house for at least 8 years.  They get full hot sun all day long.  They usually do wonderfully.  Love them.  However, this year they were doing great.  Have gotten plenty of water.  However, I just noticed that some of them have turned yellow and are dying.  I even had to pull one out and toss, it looked so bad and I was afraid whatever it was would spread. They also have some brown spots and some with brown and beige spots around the edges.   Now I have noticed that it is spreading to the other plants. Please help.  I have these all across the whole front of my house.  I always get wonderful compliments about how beautiful this is and that you can see them from way up the street.If they all die, it will look awful.  My husband has been out of work for 14 months and I certainly can't afford to put anything else in at this point.  Please - I'm desperate.

Answer
Kathy,
First of all, the brown spots may or may not be related to the yellowing leaves. It's always important to remember that sometimes there are symptoms of two or three things that are going on at the same time.

First let's talk about the yellowing leaves. When leaves yellow and a plant wilts, this is usually a watering issue, either too much or too little. You say they've gotten plenty of water, but have you felt the soil around the plants every day to see if it's really too wet or too dry?  If the soil is being kept too wet, the plants roots will rot and this causes foliage to yellow and wilt. Take a trowel and dig down a little in the soil near one of the plants that is showing these symptoms - is the soil wet or dry five to six inches down?  I don't know about Connecticut, but in my area of Massachusetts it's been really dry for a long time - only little rains here and there. So even when I water my plants for two hours with a sprinkler, when I dig down six inches the soil is still dry, especially in this hot weather.

Petunias aren't prone to many fungal problems other than some cosmetic leaf spot if the foliage is frequently splashed with water - this might be what is causing the brown spots you are seeing. Is it possible that the plants are getting watered frequently but shallowly? In such cases (usually with hand-watering or automatic sprinkler systems) the crowns of the plant -where the side branches meet the main stem and go into the soil- are kept constantly wet while the roots underneath are drying up.

There are a few viruses that attack petunias but these usually cause distorted leaves and flowers, not yellow leaves.  

Were they recently fertilized, especially with a synthetic liquid (one of the blue powders) or a hose-end sprayer applicator? If so, you could be seeing fertilizer burn, especially if the product was applied when the plants were dry.

So what to do at this point?  If your check of the soil and thinking about the watering leads you to believe that the plants were kept too wet or too dry, alter your watering so that they are getting a deep soaking less often, but for a longer period of time. Using a sprinkler or soaker hose is usually best.  If you think you might have over-fertilized or applied fertilizer to a thirsty plant, water them extra well now, and then wait a few days and see what happens.  

In any case, clip some 6" long branches off some of the plants that still look good and remove all but the top set of leaves. Take off any flowers too. Then put these cuttings in some pots that are filled with wet, fresh potting soil or seed-starting mix. (Wet the soil in a bowl or something ahead of time to be sure it's throughly moist.) Then fill the pots, stick the cuttings in and water them well again. Put these in the shade and water the pots whenever the soil is starting to dry. Petunias are pretty easy to propagate from cuttings so you should at least get a few plants out of this. If you want to up your odds, buy a bottle or envelope of rooting hormone at your garden center and dust the stems with this before you put them in the pots.

I hope this helps!
C.L.