When to plant seeds in cups?

I live in southern ontario and I was wondering when should I plant seeds into cups indoors.

I will be re-planting them outdoors later.

Thanks

Hey buddy I'm in S Ont also, I am getting ready to start vegging this weekend, I usually start 50 seeds at this time under a 25oW MH, in about a month (or when I think they are pretty healthy) I transplant them into larger containers, then they go outside for about 2 weeks getting adapted to the outdoors(in my back yard) When those are being adapted I start off 50 more under the artificial this allows me to get 2 batches of 50 vegged for planting time at the end of may, I have found that you can still put plants out in Mid-June and they will grow fast enough and mature by 1st week in Oct in this area

If you have space and light start them as soon as possible. Just day light by a window, they might get tall and lanking. This is alright, just transplant them deep burying some of the lanky stalk, right up to the leaves. Add a little light besides the window and they should be just fine.

If you don't have space to start them now, don't worry, you can start them in month outside and they should be just fine.