Expert: Long Island Gardener - 7/21/2009

Question
How do I keep my petunias from becoming leggy

Answer
When you buy them at the garden center, Petunias are almost exclusively rigged behind the scenes with all sorts of growth regulators and synthetic hormones that make them bloom like there's no tomorrow.

You pick up this flat of short, heavily branched plants bursting at the seams with flowers.

Then they grow.

Short of more hormone and growth regulator treatments, there ARE things the ordinary gardener without access to a chemical lab can do to keep the Petunia bed looking lovely.

First, make sure you plant them in the right place to begin with.  These are FULL SUN defined, plants that absolutely must bake all day, under sun, all Summer long.  That keeps their cells tight and compact, and gives them energy to make flowers.

Next, keep them pruned and pinched.

Yes, it hurts to do this.  You must remove buds and sometimes flowers.  But it has to be done.  Don't think too much about it, just do it.

Get a nice sharp pair of scissors.  Pick a section below the last flower, perhaps 2 to 3 inches from the soil/base of the plant.  Cut.  You're done.  Next Petunia.

This is assuming there are leaves below this cut.  If not, get your Petunias to branch -- cut above the FIRST set of leaves.  Branches result.  After it branches, you can cut again.  This cutting here, cutting there actually stimulates some of those hormones the professional growers use to keep their Petunias short and in flower-mode.

It's ALSO important to do this REGULARLY during Summer to keep the Petunias from going to seed.

Once these go to seed, they go to sleep.

Remember NEVER to fertilize.  If you must do something, pick up some vermicompost (Earthworm manure) or Cow Manure and add it to your soil -- you'll grow huge populations of microbes that cater to the whims of Petunias and spoon feed them all the fertilizer they need.  Chemical fertilizer is painful to Earthworms; they hate the stuff.  Spring some on one and watch what happens.  You'll never use it again.

There's a whole study of vermicompost and manure in the May 2008 issue of Applied Soil Ecology:

www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6T4B-4RM896G-1&_user=10&_rdoc=1&_fmt=&_orig=search&_sort=d&_docanchor=&view=c&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=abccd62a0686b6561622160587a446e1

The study is called 'Influences of vermicomposts, produced by Earthworms and microorganisms from cattle manure, food waste and paper waste, on the germination, growth and flowering of petunias in the greenhouse'.  People like me think this is really interesting.  Maybe you will too.

Don't over-water your Petunias, either -- especially in a Summer like this where it rains every day or more.  You grow Petunias to see them bloom.  Not to admire their beautiful leaves and stems.  Fertilizing Petunias will give you lots of leaves -- and these are not foliage plants.

Finally, when the blooms are past their peak, remove them.  Spent leaves produce ethylene gas, which inhibits and sometimes even halts flower production.

Got that?

All of this is assuming you did not purchase trailing Petunias, with DNA meant for baskets dangling from the ceiling on the front porch or spreading right and left on the ground.

Thanks for writing,

THE LONG ISLAND GARDENER