Hi there. I don't know what you mean by 'red ash', but wildflowers, like most plants, need soil in which to grow. If you do a google search, you'll find lots of info on how to prepare the soil, etc.

Most wildflowers like, open, sunny conditions and poor soil. You could probably choose a selection that prefers damper conditions, but they'd still like some sun and won't like being flooded periodically.

I don't know what you mean by 'red ash' either... but it doesn't sound as if its suitable for planting anything in.

Probably best to consider pots at the front and maybe shrubs or perennials to the back, in the ground.

Red ash would appear to be a form of hardcore so, as already said, nothing will grow in it... Some nice pots or containers will brighten the front up.

Containers are better if you're renting because you can take them with you.

It's probably only worth thinking about planting in the ground if you own the flat or have a long lease and want to go to the effort of improving the soil.

For the front, consider window boxes which you can fix on brackets. If you use pots at the front make sure that they're big enough so that you can weigh them down with a few bricks inside.

A possible problem with containers might be theft though if the red ash area is open to the road. And those collections of wild flower seed do produce a nice display in the first half of summer but in the second half when they die off they can look rather sad and untidy. Our council has planted them these last two years and quite honestly they look a mess at the moment though they were pretty earlier..

For the back which can flood containers sound the best idea. Make sure they have good drainage holes and stand them on something to raise them off the ground so the water can escape through them. If its very shady most flowers will struggle but there are lots of plants that enjoy shade - hostas, heucheras, ferns, and some variegated small shrubs. If it does get some sun fuchsias might do well. All containers will need regular watering unless its been raining.

I was trying to suggest the possibility of theft without wishing to cast 'nasturtiums' on the neighbourhood. The other problem with containers on the front is that they can completely innocently wander off in a high wind if the area is open and the containers aren't fastened down.

The red ash is probably a mix of fine gravel and crushed brick - it is used to suppress weeds but allow the area to drain. If it's a block of council (or other social housing) flats it may be that the council goes around periodically and sprays the area with their version of Pathclear. It might be worth asking the landlord if they have a weedkiller programme.

Some shallow planters with Crocuses in would brighten up the area in the spring. Remember to get purple and white ones, the birds steal the yellow ones.