Expert: C.L. Fornari - 1/4/2009

Question
Hi!

I have ben growing petunias for the pst many years in balcony containers but
find that after the initial 1-2 months of full bloom they die. My balcony is
west facing in Dc area. However in the same pots, geraniums grew and
survived wonderfully till dec end.

Thoughts?  

Answer
Sanita,
Geraniums are a more long lasting plant, and deadheading them is pretty simple. Did you use the regular petunias that come in six packs? If so, these need to be deadheaded by cutting the stems below the flowers in order to remove developing seeds. If you don't do this they soon quit growing, flowering and die. From a plant's point of view, their mission is to replicate their genetic material and once that has been accomplished (seeds) they are done.

The new Supertunias or Wave petunias are a bit different. These don't have to be deadheaded, but they DO need a high rate of fertilization and pruning. In order to keep them full and blooming you need to cut 3 stems back by half every week, starting when they are full and don't need it. Most people wait until they are already looking bad, and then it takes far too long to recover.

The other issue you might be seeing concerns drought tolerance. The geraniums prefer to go a bit dry between waterings, so if you don't water them during a hot, steamy day or two they'll still be alive. If you let the petunias go dry they often die.  Also, wilting stresses a plant so if there were days when you didn't get to the watering before the petunias wilted, they would be more and more stressed as the summer goes on, and those hot days in strong afternoon sun can do them in.

So I leave it to you to decide which plants would be best for the coming season.

Should you be looking for a companion plant for the geraniums that is also drought-tolerant you might try portulaca or purslane.  You can buy portulaca (moss rose) in six packs and Proven Winners sells a great purslane (portulaca with flat leaves) in many colors, available in small pots.  You could plant three or more of these around the geraniums and have other colors cascading over the basket or box.

all the best,
C.L.
www.gardenlady.com
blog: www.wholelifegardening.com