I'd suggest going with plan B this year as it is way late to be starting petunias from seed now given their slow germination rates. But if you want to give it a try then yes you need a good source of supplemental light. It does not need to be an expensive "grow light". As the FAQ here on lighting says common inexpensive fluorescent shop lights is what most use.

Personally as a nursery grower I'd like to warn you against the flower towers because of all the problems they have but I have lots of customers who don't believe me at first either so give it a try and see if you can make it work for you. ;-)

In April you should still be able to find smaller wave plants available if you are in the north. But if you can't then you will just have to cut a bigger X. Keep in mind that you have to work from the bottom up so that you can have 1 hand inside the tower and one outside to get each plant in.

Hope this helps.

Dave

Thanks a lot for your advice! Ok, I believe you and won't try the flower tower. I am wondering why that causes issues though (mostly because I want to know if I planted a couple of wave petunias in the side of a hanging basket, through a coco liner, would that also be problematic)? I like the big full basket look but haven't tried that technique before and im not sure if that would pose any issues. Thanks again!

It's been a LONG time since I grew petunias from seed, so I don't remember the exact time it took me, but I'm in Z5 and I wouldn't be sowing them yet for a June 1 frost-free date.

Re your general questions about growing with or without lights, I have a few spots set up with double 4' fluorescent lights for my seedlings indoors, but I do use sunny windows for overflow. On nicer days, I can bring trays of seedlings outdoors to a protected mostly-shaded area on the porch and I also have a coldframe that holds 6 full trays (placed in shaded area for seedlings).

Party makes a good point that if you can't have them outside until June then you have time to grow from seed. That sounds quite late to me as most of the zone 5 garden clubs want theirs by 1st week of May. But if you can't plant them out until June then you won't have the full basket look until well into the heat of mid to late July.

The full basket look that you buy at most nurseries has been growing inside in a greenhouse for 45-60 days before going out for sale.

" I want to know if I planted a couple of wave petunias in the side of a hanging basket, through a coco liner, would that also be problematic"

Yes. They don't hang well and the weight pulls them out plus it causes a big drain hole for the water to drain out too quickly. And if you want to plant in holes in the sides of a hanging planter then you need to use sphangum moss not a pressed cocofiber liner.

You want to plant them at the outer edges of the top so they drape over the sides and hang down the sides.

Dave

I start wave petunias indoors every year using cheap shop lights. I start them anywhere from late February to mid March. I picked up the shop lights for $20 a piece and put one cool and one warm bulb in each. We hang them from a 4 tier shelf. The shelves are maybe 2' by 4'. They each can hold 4 basic 72 cell seed starting trays. Initially, I used two shop lights per shelf. Now each shelf has three. As a home grower, this is an effective, extremely economical route. We also start all of our veggies this way.