Question
I have no experience with flowers before.  I planted wave petunias from seed.  After about a month now, they are about 6-8" tall, and I don't know if I should cut them back or how or where to cut them back. I have them in hanging baskets and each plant has about 6 stems coming off the main stem (alternating on opposite sides of the main stem).  Any information would be helpful.

Thanks  

Answer
You can't go wrong with Petunias. Growing these from seed, however, on your first try takes a VERY green thumb. Bravo for succeeding on your first try.

There are actually 2 kinds of Petunias, thanks to the wonders of modern science.  One is the spreading, trailing Petunias for hanging off the porch in baskets or filling in flowerbeds -- Wave, Supertunia, and Suntory Petunia hybrids.  This is what you are growing.  These are the top sellers in this country.

The seed-propagated 'Wave' series was developed in Japan by the Kirin beer company. Ball Horticultural Company licenses the right to sell seed in the U.S. and has set up a special website just for people like you:

www.wave-rave.com Ball Horticultural Company

You may however be ready for something a little more challenging.  And so I'm also going to refer you to the company's OTHER website, where it posts some hard-hitting technical advice for professionals who grow Waves from seed:

www.ballhort.com/media/Culture/PAS/PetuniaShockWave.pdf

Yes, you've been there done that already, but for those who have not, let's just summarize the hard facts Ball provides to maximize success with Petunia seeds.

Briefly:

Ball recommends a sterile growing medium w/ a pH around 5.5-6.0. Waves germinate, preferably uncovered, in 4 days when you keep the soil temperature at 72-76 degrees F and provide constant -- and I do mean CONSTANT -- moisture.

After the seeds germinate, you should reduce the soil temperature to 68-75 degrees F and provide semi-sun exposure; a nitrate ferilizer low in P and constant moisture will get these growing.

When the first leaves have appeared, cool down the soil further and maintain it at 65-70 degrees F; stop watering until it is almost dry. As for nutrition, they advise, 'Minimize Ammonium form Nitrogen fertilizer to avoid seed elongation.'

Finally, as they begin to branch out, grow the seedlings cool, at a soil temperature 60-65 degrees F, and move to a full sun exposure.

These guidelines are not written in stone -- obviously you know what you are doing, and you will get better with practice. Expect to make mistakes.  You learn from them, and you get better and better w/ every one.  It's hard to swallow that but it's plain and simply the truth.

This brings us to your question.

You can plant your Petunis, if you so desire, in a 10 inch basket with 3 to 4 plants in each basket.  They will fare best if the day is not hot, air temperature hits 61-75 degrees F and nights 57-65 degrees F.  But you don't have control over the weather.

This is in contrast to the old Petunia patches that bloomed best in solid, sweat-inducing heat.

Note advice from the aforementioned pro's: 'Shock Wave Petunias require more fertilizer than is usually recommended for Petunias.'  Long days will get these flowering sooner, say the folks at Ball.  Seems there are different sun demands by different Waves to perform at their best. Ball posts their advice.

Most people over-fertilize and over-water Petunias, so the advice I usually give is to leave them alone.

Your new, more perfect Petunias don't even need pinching anymore -- that step in which the gardener reached down and with his thumb nail and index finger, 'pinched' the stems just above a set of leaves to keep them short, stocky and abundantly blooming.  Texas A&M AgriLife Extension Service points out, 'Unlike old-fashioned petunias, it's not necessary to pinch back or deadhead Wave varieties - they can take care of themselves.'  You can read their full page on Petunias here:

aggie-horticulture.tamu.edu/extension/newsletters/hortupdate/mar08/TenWays.html

Feed these a fertilizer LOW in Phosphorus (the middle number on the N-P-K breakdown).  Remember, Petunias are HYPERsensitive to P.  It has the negative effect of actually blocking off Iron, Calcium and Magnesium.  The less P, the better -- ZERO is best!

This is an excellent plant.  Several 'Wave' varieties have snared awards as All-American Selections.

Keep up the good work.  And thanks for writing.

THE LONG ISLAND GARDENER