Have you thought about some annual and perennial plants rather than shrubs? 18 inches is quite narrow.

IMHO .... the solution to your dilemma ... is to make a 4 foot bed on the far side of the sidewalk ... and plant something in the middle.. 2 feet from the sidewalk ... and plant your trees/conifers/shrubs there ...

and then fill your 18 inches.. as noted in the first reply ...

nothing.. shrub-wise.. will fit.. planted 9 inches from the house ...

never forget... foundation planting are planted to HIDE the foundation.. NOT ON THE FOUNDATION ... you are in a box.. and realizing the box is way to small ..

you might also want to think about a trellis of some kind.. on the left corner.. and grow a vine up it.. to soften the corner.. maybe clematis???? [though i donjt know about clems in z8]

ken

I removed the concrete blocks that previous owners put on the bed and it seems the space is actually 30 inches which is still narrow. Will any shrubs fit now?

I'm very new to gardening. I forgot to mention that my house faces west so needs something very drought tolerant. I don't mind the initial work but I would like something would require minimal maintenance.

@ken_adrian I really like the idea of adding a trellis on the corner

Texas,
I have same zone as you, I also have dry conditions here, this Hicks Yew is about 4 years old, I have pruned it some.
I use this for the same reason you want.
{{gwi:284239}}

you are welcome on the trellis idea..

but did you catch this part: the solution to your dilemma ... is to make a 4 foot bed on the far side of the sidewalk ...

the number one error of newbs.. is thinking that foundation plants are planted ON THE FOUNDATION ...

no.. they are not..

they are planted well away from the foundation ... to HIDE the foundation ...

i used to take the lawnchair.. and an adult beverage or two.. and go sit at the curb, facing my own house ..... trying to envision.. what your goals are.. in regard to the space provided ... meet a few neighbors too ....

right now.. your only goal is to jam something in that tiny space.. and that is why you are struggling to figure out what ,....

your proper goal.. is to figure out.. how to architecturally enhance you house .. forget about that TINY SPACE .... and that all begins.. on the other side of the sidewalk .....

i will say it again .. you plant out in the lawn.. on the far side of the sidewalk ... specimens that grow large ... for an architectural 'look' ...

and then.. in your small space.. you plant some annuals/perennials.... for some eyeball enjoyment... as you trod down your walkway.. hidden by the bigger plants.. further out ...

ANYTHING.. that will grow bigger than the footprint provided.. does NOT belong in any given spot ...

i wish you luck

ken