Expert: C.L. Fornari - 7/8/2008

Question
I have mini supertunias in boxes and once again this year
some of them have gotten lanky-the leaves are stiffer and
the flowers are shaped more like bugles and do not open fully.  What am I doing wrong


Answer
Cindy,
I'm assuming that the boxes are in at least 4 hours of strong sun, either in the afternoon or the late morning including the noon hour. If they are in more shade than this, it could cause the flowers not to open fully.

Secondly, I'm assuming that the boxes don't get too dry - in hot weather you may need to water them in the morning and again in the afternoon. If they are drying out frequently this could also cause what you're seeing.

And thirdly, I'm assuming that you are saying that ALL of the flowers aren't opening. If SOME of them are open and some aren't, than this is normal in that the flowers that will open the next day will be bugle-shaped and those that were open the day before and are wilting will as well, but the ones that have opened that day should be wide open for at least 24 hours.

So if you've ruled out 1, 2, and 3 above (or a combination of those - sometimes what we see on plants is the result of a couple of things) then I'd try fertilizing them well and cutting some of the stems back by 2/3 of their length. It is normal for petunias to bloom ONLY at the end of the stems, and as the stems get longer we notice more and more old stem with the flowers at the end.  Fertilize with a liquid fertilizer that either has a slightly higher first number (more nitrogen) or even numbers across such as 10-10-10. The so called "bloom booster" fertilizers that have a high middle number aren't good for these type of petunias - they are nitrogen hogs!  WATER THE BOX WELL BEFORE FERTILIZING - never fertilize a thirsty plant. And if you've already fed them, ignore this part of my answer.

Cutting two or three stems back by 2/3 every week will produce shorter stems that will double and produce two flowering branches. Ideally, you should start this cutting back BEFORE the plant gets leggy - hard to do, I know, because when the plant is looking good it's difficult to make yourself cut them back!

How to keep petunias full and bushy is one of the most frequent questions I get - in fact, there is an article about petunias on my website right now: www.gardenlady.com

I hope this helps!