pot plants for quick growth

Hi, I wonder if anyone can help?
I am very new to gardening and know pretty much nothing!
Anyway, I am helping to run my son's school summer fayre and we are doing a paint a plant pot with a flower to go inside, so please can anyone advise of some flower seeds that I can sow now to be ready and looking relatively pretty within a few weeks? I had sown some marigolds a couple of weeks back on the advice of a friend, but unfortunately a couple of snails got into my greenhouse and devoured the lot! Also- any tips on stopping this happening again?
I really don't want to have to buy them from a garden centre as we need about 100 plants and are trying to keep costs to a minimum!
Many thanks!
Jodie x

 

Nasturtiums, cosmos, Love-in-a-Mist, sunflowers? Why not just have another go at marigolds? You might perhaps consider cress, radish or cut 'n come again lettuce?

Why not have a look in your supermarket they frequently sell packets of seeds and places like B&Q and Homebase have loads of seeds (less than £2 per packet) some often labelled 'for children' since they're reliable, quick to grow and pretty indestructible!

As for the snail problem - well, you can either use slug pellets or those copper strips or just make it difficult for the little critters by putting seed trays on staging or, at a pinch, on a couple of bricks (standing on their 'short' ends). Just make sure there are no visible slugs or snails around the underside of the lip on seed trays - if you want to 'catch them in the act', you'll need to go after dark, armed with a torch!