Olive trees, kumquat trees, bay laurel

This might not be too exciting of a suggestion, but I think trailing plants are always visually interesting in tall planters, especially as slender as the planters you describe. Not sure about winter conditions, but a trailing succulent could be stunning. Also love the idea of asparagus ferns. Or purple hearts?

Happy planting!

I like a single tall totem cactus (don't know any official names) in combination with trailing succulents. Low maintenance especially with that afternoon sun.

In fact, my front entry is tall but narrow and I have been on the lookout for tall skinny planters.

I like the idea of the tall cactus with the trailing. A bit of height would add some drama :)

I have 2 large/tall pots in my entry that gets full afternoon sun as well. I planted lavender starflower vines in each one (I also put in a trellis in each pot) and they have done well. Flowers are really pretty also.