There were some questions posted on Dave's Garden and here is a copy of my response.
Hi everyone. I started a new job with long hours and have been overwhelmed trying to pot up all the "flip'n" petunias that I seeded this year. I have totally run out of space and it will be a few weeks until I can put them outside. We have a cold wet forecast for the next week, so it will be challenge.
Fragrance: The Blue Waves are fairly fragrant. Hot Pink Tidal Wave is very fragrant. Supertunia Dble Peppermint is very fragrant too, but not sure that I like the smell. We are very dry here, so most "fragrant" flowers are less intense than a more humid area. There may be other petunias that are fragrant & I never noticed.
Feeding: I use a slow-release 14-14-14 fertilizer by Smart-Cote for Hanging Baskets. When picking your fertilizer, be sure that it includes macro & micro nutrients as well (not just filler). Things like calcium, magnesium, iron, zinc etc. Put the fertilizer about an inch below the surface. The fertilizer will need good soil contact, moisture and temperatures above 20ºC or 68ºF to actually work. Dry soil, cold temperature will affect the release of nutrients and the plant absorbing/uptake of the fertilizer.
Petunias a fertilizer junkies. They really need consistent fertilizer throughout the growing season. So if you have them in pots, which 90 % of the petunias end up growing in in my yard, the nutrients will be depleted of the soil by the continuous watering (next paragraph) mid to late season and especially if it is hot. So plan to supplement with additional fertilizer. For me, this is mid to late July. I give them a blast of water soluble fertilizer every 2-3 weeks until late September or hard frost. I find that Miracle Grow Ultra Bloom or a bloom booster of some sort (high middle # for NPK) helps with the petunias to continue to pump out new buds and give lots of blooms.
Watering - If it is warmer than 23ºC or 73ºF, I water. Of course in early spring/summer, you should stick you finger in the soil to check, but by mid season the plant will be fairly rootbound and will go from a little dry to parched in no time. Deep watering is the way to go. Water until you see water coming out of the drain holes. That's the perfect amount. Really it is. Just so you know, Calibrachoas are not forgiving if they become parched even once. They will stop blooming in protest and within days they look aweful. Recovery is a slim chance.
What's your pot size? Don't cheap out with the size of pot. If you want big plants, you need room for the roots. Some petunias have a large root system, so be sure that the pot is big enough. Tidal Waves need minimum 14" pot for a single plant. I have put 3 Waves in a 12" pot with good success. Line all wire baskets with plastic, other wise they will dry out too fast and you will not be able to keep up with watering it. So check the stated mature size of the plant. If it is more than 3 feet a 10" pot will not be big enough unless you are giving it greenhouse care with constant feeding and drip water. Try 16". And if you have companion plants as well, you need a bigger pot.
Put mulch on your pot when you first plant it. I like mini bark nuggets since they are cheap, very light weight and look nice. When the plants are small and there is a lot of soil in full sun exposure, the young plants with their small roots can dry out fairly quickly. If you mulch, the moisture level will stay more consistent and it will be no time until the plant fills out enough to completely cover the soil in the pot.
How about a nice pre-planted hanging basket? You will never be able to buy all the plants in the combo at that size for that much money. It's a great deal. Problem is that in about 4 weeks it starts to look a little worse for wear and in about 6 weeks pretty pathetic. so here's what you do, enjoy your basket for a few days (remember in the growers it was constantly drip irrigated, fertilized and was in optimum growing conditions). If you are lucky the place you bought it from actually watered it before it was parched. And you can bet that they did not continue the fertilizing for the week or so that it lived there. Also, the plant material is usually quite robust and the root system is probably close to maxed out for space. So plant it into a bigger pot with slow-release fertilizer. Put a 10" into minimum 18". Your new combo will look fabulous until the end of season.
Pick your petunias variety. For me, I don't like deadheading. All the varieties that I grow are described as "free-flowering or everflowering". If they require deadheading to flower, it's not suitable for me. Some petunias, especially the dbles, only flower at the ends of the stems. so look for that characteristic. You may want to have a "ball" look so you will need a petunia that sets out blooms along the stem rather than just at the end. Another thing with petunias are that most are daylight sensitive. They will stop producing buds with less than 12 hours of daylight. Yes, that includes the Waves. Easy Waves are less forgiving.
My favorite Petunias: Vegetative: Vista Supertunias (any color) and Seed: Blue Wave, Tidal Wave & Shock Wave
Anyways, hope this helps and good luck with your petunias.
Oops forgot to mention the soil mix. I use Premier Pro-Mix BX for all my containers. Great stuff and have used it for years
