what can we plant underneath the trees?

Hi Folks.
I am leading a group who are creating an communal allotment and garden on a council estate. The council have given us the go-ahead to use a plot of land on the estate and we are getting things ready now!

The plot is a decent size, but over half of it is taken over by trees. There are 4 trees (I can't remember now what sort they are, but they are well established and deep rooted).

We are going to create vegetable patches around the trees. Underneath them we were going to buy some raised beds, but the council have pulled the plug on the grant we were applying for. We won't be able to buy any raised beds now. :blink:

I was thinking we could plant something underneath the trees that flowers. Does anyone have any ideas of what we could plant?

We as a group are novices with limited gardening experience (I have veg and flowers in pots but not in a garden) so any help or advice would be greatly received!

Where are you?  You could do with trying to get a load of freebies if the council aren't going to help.  You could also do with trying to plant stuff that will give a show of flowers for as long as possible through the year - so if you can start with some shrub or bulbs that flower yearly - the idea of the geraniums is great - especially if you do the Chelsea chop with them - i.e. cut them back when the Chelsea flower show is on and they'll come back and flower again later in the year.  I would suggest you try all open gardens, National Trust gardens, garden centres etc in your area and ask them for cuttings/spare seedlings etc so that you can do as much as possible for free!

Things like snowdrops are planted in the green so you see them for sale (I got mine on ebay) about now, I think bluebells are the same, but a bit later in the year.
But you are right the other bulbs can't be planted until autumn 

Helebores are lovely too - if you can find someone who has them, I am sure the larger one's can be split.