What's the matter with these petunias?

Question

I have never had trouble growing these before. This year I planted some in window boxes - they grew and flowered great for about 3 weeks, then ppppptttthppp - they look sick, and are hardly flowering at all. They are on the south side of our building, get watered when they are dry, and it has only been about 25 C, so isn't very hot. Any ideas how to perk them up? I put fertilizer in one box to try, but it didn't make any difference.

Answer 1

Hm. I can only give you a few ideas.

For one, Petunias are very, very high maintenance. They need to be deadheaded regularly, you probably know that. So make sure you are picking off the dead flowers so they don't go to seed. Seed production robs energy from the plant.

You might have some luck if you pinch them back a bit and give them a dose of fertiliser, probably something like 15-30-15 or 20-20-20, whatever you have. At the beginning of the season, put in slow-release granules (14-14-14) so you don't need to worry about over or under feeding. Also, make sure you're only feeding once every 2 weeks if you use a chemical (mix with water) fertiliser. It can be very tempting to over feed, but stop yourself. It will burn the plant.

Hm... Did you plant them in fresh soil this year? Using old soil (with the old roots still in) can cause a couple of problems. Did the soil come from a sterile mix or from the ground? You need to always use fresh, unused, sterile soil in planters. Old soil should be composted.

In planters, root space is scarce so you need to make sure you didn't overplant (plant too many) so the plants aren't competing for root space. The rule is "if it looks fully grown when you plant it in the spring, you've overplanted".

If you pinch them back pretty hard and give them a dose of high phosphorous fertiliser, they might recover in time to flower again soon. Thin out a few plants if you think you overplanted.

Good luck!

Answer 2

In my own yard I have 19 pots of petunias, so I love them. Have you pinched them and do you dead head them every day. To dead head them you must take off the old flower so they can grow a new one. And to pinch them you go down a little ways and you pinch the vine off that will make it spread out and it will fill your planter with wonderful flowers. I dont know where you live but they also like lots of sun. I hope its not to late so that you can enjoy these wonderful flowers. you do need to use fertilizer about every 7 days I use miracle grow.

Good luck and please dont give up try again next year you will love them.