window box advice for absolute beginner

[godhelpmeplease]

I have a south facing top floor window box in London and want to get something in there asap. I am a total novice so please bear with me. The actual box is concrete/cement and part of the building so I don't think there are major weight concerns. It's about a couple of metres wide but I think it's best if I take it one step at time.
For my sanity I want to be able to see some greenery from the desk where I work so plants should have a bit of height to comfortably meet my eyeline. Flowers aren't essential, greenery all year is crucial, especially in the dreaded dark months. I love succulents, grassy/fern-type plants, Mediterranean plants. I work from home so can manage frequent watering if necessary. Many thanks

Geraniums are gorgeous...begonias too. My brother had tobacco flowers in his...lovely red colour. Intersperse with some minature confiers and some ivy. Just water daily in summer....but you're heading into winter now so maybe these things I'm mentioning are better in spring.

For winter, choose winter pansies...add some ivy and again, the mini conifers.

We have a hebe midnight sky, it has very dark purple glossy leaves which were stunning all winter, and then in summer it gets greener and flowers purple. Lovely plant, I am seeking another for nearer the house so I can admire it more over winter.

Would look glorious against that fence.

Oops wrong thread! But it still sounds like a good pick for you.

Can you post a photo or draw a diagram to show the dimensions, how deep it is and how far below the window it is so we can work out how tall the plants need to be and what you can grow in it?

Do you want to plant it up once with perennials or are you happy to redo it it once or more a year?

Now is actually a great time to plant a window box as you can put in layered spring bulbs to flower at different times then add winter bedding or perennials on top.

if it's up high and south facing then Mediterranean stuff and succulents should be really happy in there. Some grasses too, but ferns not so much as they tend to be more shade loving.

What Cheshire said - how big/deep etc - and crucially - is it windy? that's going to have a big impact on both the type of plant and everything drying out really quickly.

Gosh thanks for these lovely plant suggestions! Width is over 2 metres but I want to take baby steps so would be happy to cover no more than 1 metres for now.
The short side is 28cm, the depth of the trough is 32cm but plants would need to be quite elevated and vertically inclined for me to see them as the top of the trough is below the window pane, photo attached. Although it's only a third floor it is pretty exposed as it's a wide street and there are no buildings nearby
Cheshire I think for now evergreens only, until I see if I can get the hang of gardening and then I might add some other plants.
Any tips for sources to get the prep right - ie. pots, soil, compost, fertiliser etc? You can't overestimate my ignorance on gardening!

Ok, it's a space for pots rather than an integral window box.

You need self watering pots that have a reservoir, otherwise you will be hanging out the window watering twice a day in summer. Lechuza are excellent, Elho also have a good choice with lots of fun colours, Wilko sell Clever Pots as a cheap alternative. Stewart also make budget versions (from Amazon or garden centres or DIY stores).

You don't want anything too tall or bushy as it will block the light. You could have a couple of Mediterranean quarter standard plants (like a lollipop shape) or cut into a spiral or pyramid at either end eg rosemary, bay, olive lavender, even holly. Box, hebe or Ilex crenata balls could look good too.

www.marksandspencer.com/bay-tree/p/flp60178573?extid=ps_ps-gpla_ggl_flowers_food__-UK-css-_&gclsrc=aw.ds&&gclid=Cj0KCQjwg7KJBhDyARIsAHrAXaE4reC3EMGtccniyb74WGO3h2gp0oxJ--yTyTTSdGQF8bQTbfWunfQaAvnZEALw_wcB&gclsrc=aw.ds
www.charellagardens.co.uk/buxus-sempervirens-ball-30cm-5-litre/?gclid=Cj0KCQjwg7KJBhDyARIsAHrAXaGC8hjVxrIjUbeUE0jBFEEHzhfekIOlRpCHFM5od605K5bhoeuv2RQaAlKYEALw_wcB

Geraniums/pelagoniums are the easiest, low maintenance Mediterranean window box plant. They can flower for about 9 months on a sheltered London balcony, they are drought resistant if you forget to water them and evergreen (have leaves all year round). You can get trailing and upright varieties. Salvias are good too but would need trimming every year. They have the advantage that the flowers are on long stems so you will see the flowers without the plant blocking the light.

www.fibrex.co.uk/collections/pelargoniums
www.norfolkherbs.co.uk/plant-type/salvias/

Look up how to lasagne plant bulbs so you get different flowers each month eg giant snowdrops (Jan), miniature irises, crocuses, early daffodils (Feb), then there is a huge choice after that. I would underplant with bulbs around the shrubs and then have some pots of bulbs with flowers on top (the bulbs will find their way into a gap).

If you go for something like geraniums, the bulbs will need to be the taller varieties. I would grow violas/pansies around shrubs on top of bulbs (Cool Wave can bloom all year round in London) or a creeping thyme (I love thyme lemonade, it really does smell like lemonade). You might not see them unless you are close to the window but they are better than a view of bare earth and will help keep out the weeds!

www.sarahraven.com/products/velvet-winter-windowbox-collection?gclid=Cj0KCQjwg7KJBhDyARIsAHrAXaGmd-P2VsF7Zr-UH5BHk9939-YKhuGaUFUaMj0CrYvbDgITVXHlscEaAoQNEALw_wcB&gclsrc=aw.ds
www.thompson-morgan.com/p/pansy-cool-wave-collection/WKC1064TM?source=google-prodex&gclid=Cj0KCQjwg7KJBhDyARIsAHrAXaHov1WFly3uIwSGt78E0ugQ7PzbzaBKr1lWiOrOshOWa6jwXJQQN0QaAogHEALw_wcB
www.norfolkherbs.co.uk/product/thyme-lemonade/

I also put aquarium gravel on top of my pots. It helps reduce weeds (which will be a pain to get rid of as you don't have easy access to the space) and slugs, and it looks neat.

Cheshirecat you're a star, thanks so much for these great suggestions. I love all the plants you've listed and now know what a quarter standard plant is. As for lasagne planting, who knew such wonders existed, this will become my autumn and winter obsession!
The pot suggestions were also great, again in my ignorance I had no idea such a marvel as a self-watering pot existed...
This is the one flat I've lived in where I'm not worried about plants blocking the light, the windows are so wide and numerous that in the summer I have to have the blinds half lowered as it's too much and even in mid-winter there's enough light.

Oh, I might have confused you! They are called standards, quarter/half refers to the height compared to a "standard" standard of 5/6 feet

You could probably haggle yourself a bargain standard bay or olive tree at the end of the day in Colombia Road. I've also seen standard hibiscus and lavender there in the early summer. It's best to get there early to look around then go for brunch and come back to see if what you want is still there at packing up time when everything is being reduced.

Clifton Nurseries in Maida Vale usually has some amazing topiary (plants pruned into geometric shapes) but they are eye wateringly expensive... I would stick to cheap and cheerful until you have developed your green fingers. It's worth a browse for inspiration and afternoon tea in their lovely cafe though.

Cheshirecat Colombia Road is a welcome reminder, I live not far at all but haven't been for years. Clifton and Petersham Nurseries are great for ideas and inspiration even if beyond my budget. I will proceed one plant at a time as you suggest. Thanks again