[Longshanks]

I have a 2Mx2M space to fill on my allotment and wanted to plant some flowers and shrubs. I think I can plant bulbs now, but also wanted to put it some perennials such as fuchsia, grasses whatever including  a few dahlias. I'm just not sure when I should plant them - now or wait until spring.

[New shoot]

Spring flowering bulbs are planted now and you can also plant perennials.  Dahlias are a bit trickier.  If you have light, free draining soil they will be fine, but mulch over the tops before the really cold weather.  If you are on heavy wet soil, it can be a bit of a gamble as to whether they make it through.  I lift mine and store the tubers in the shed.

A lot of garden centres will be selling off big 2L perennials over the next few weeks.  I picked up a few the other day.  In the spring you can get small starter perennials that are quite cheap, so I would see if you can find some bargains and if not, fill the spaces next year 

[Longshanks]

Great answer. I'll follow that garden centre tip up, but from what I've seen in B&Q, prices aren't exactly cheap for shrubs. I'm on good old London clay, so will bear in mind what you say.

[jaydig]

When I was younger I used to hate dahlias, and thought them to be an "old person's" flower.  I don't know if it's because I am, indeed, now an "old person', or that the variety in shape and colour of dahlias has improved so much, but I love them for cut flowers.  I have been cutting from mine since June, and they will keep going until the frost cuts them down.  Worth every penny spent on them, and very productive for a small space.