The bookshelf styled with trailing greenery between the spines is one of the most reliable images in interior photography. It is also, in light terms, the most demanding place in the room to keep a plant alive, and it is worth knowing why before you commit a plant to one.
A bookshelf is the worst case of every shelf problem
A shelf near a window with widely spaced boards is a good plant position. A bookshelf is the opposite of that in four ways at once, and they compound.
It stands against a wall, usually not the window wall. Bookshelves go where there is uninterrupted wall, and uninterrupted wall is by definition wall without a window in it.
Its boards are close together. Shelves are spaced for books, which are short. Every board is close over the one below it.
It is deep. Deep enough for books means deep enough that the back is a long way from any light arriving from the side.
It is full. Books occupy the space light would otherwise cross, and they are opaque.
Put those together and most of the volume inside a bookshelf receives very little light. The University of Illinois Extension puts Low Light at a north window a few feet away, an east or west window 3 to 10 feet away, or a south window 15 to 20 feet away. The interior of a typical bookshelf is at or beyond that, and no arrangement of plants changes it.
Which means the usable positions are the edges
This is the practical answer, and it is a short list.
The top. No board above it, and generally the brightest part of the unit. If the bookshelf is anywhere near a window, the top is a genuine plant position and it is the one most worth using.
The front edge of any shelf. Light arrives from the room side, so the front few inches of each board are meaningfully brighter than the back. A pot at the front edge is in a different band from the same pot pushed back against the spines.
The end nearest the window, if the unit runs along a wall that has one. Per the table above, a few feet along the shelf is a real change.
Not the middle of a full shelf. That is the darkest usable volume in most rooms and it is exactly where the photographs put a small plant, because visually it fills a gap.
The trailing habit is doing most of the work in those photographs
Worth noticing what you are actually looking at in the image you liked.
Almost every attractive bookshelf-with-plants photograph uses trailing plants placed high, with the growth falling down across the shelves below. That arrangement is not incidental. It puts the plant itself in the brightest position on the unit, the top or a high front edge, while the part you see hangs down through the darker volume where a plant could not live.
The greenery in the middle of the shelf is foliage, not a plant position. That distinction is the whole trick, and it is why the look works while a small pot placed on the third shelf down does not. Trailing plants for shelves covers which habits fall well and how far.
The books-and-pots question
A practical point that is about placement rather than care.
A pot of soil sits above paper. Whatever else is true, that is a container of damp material directly over books, on a piece of furniture that is usually not sealed and frequently not level.
That is not an argument against the idea. It is an argument for deciding, deliberately, which shelf you are willing to have that over, and for keeping the arrangement somewhere you can see it rather than at the back of a high shelf you never look at.
The version of this that goes wrong is the pot on a high shelf that nobody inspects, above the books that matter most.
If the bookshelf is nowhere near a window
Then it is a Low Light position throughout, and there are three honest options.
Use the top only, with something that suits the band the top actually sits in.
Choose genuinely low-light plants and accept holding rather than growing.
Do not put living plants in it. A bookshelf is already doing a job. Filling its dark interior with plants that will decline is not styling, it is a maintenance schedule.
If the unit sits near a north window, note that the Illinois table puts directly in front of a north window at Medium Light, so the window-end top shelf may be usable even though the rest is not. What a north-facing window supports covers that band.
Making it look right, once the light is settled
Do not distribute one plant per shelf. Evenly spaced small plants read as decoration applied by rule. Two or three clustered near the top, with something falling, reads as intentional.
Leave gaps. A bookshelf that is full of books and full of plants is visually full twice over. In a small room that reads as pressure.
Let the trailing growth cross in front of the spines rather than sitting on top of them. That is the part of the look that is genuinely attractive, and it costs no shelf space at all.
What this page is not covering
Anything about how the unit is fixed, what it carries, or securing it to a wall. Plants and pots are heavy, a tall unit is a tipping question, and both deserve better than a paragraph from a plant site. That is somebody else's subject and worth reading properly.
If you have pets
A bookshelf puts plants at climbing height, and a cat that gets onto shelves will reach the top one first, which is exactly where this page recommends putting the plant. Check any plant, by botanical name, against the ASPCA's toxic and non-toxic plants database before it goes up there.
Frequently Asked Questions
Can plants live on a bookshelf?
On parts of one. A bookshelf combines four problems at once: it stands against uninterrupted wall, which by definition has no window in it, its boards are spaced close together for books, it is deep, and it is full of opaque objects. Most of the volume inside it sits at or beyond the University of Illinois Extension's Low Light band, which it puts at a north window a few feet away, an east or west window 3 to 10 feet away, or a south window 15 to 20 feet away.
Where on a bookshelf should a plant actually go?
On the edges. The top, because nothing is above it and it is generally the brightest part of the unit. The front edge of any shelf, since light arrives from the room side and the front few inches sit in a different band from the back. And the end nearest the window if the unit runs along a wall with one. The place to avoid is the middle of a full shelf, which is the darkest usable volume in most rooms and exactly where photographs put a small pot.
How do those styled bookshelf photographs actually work?
They use trailing plants placed high, with the growth falling down across the shelves below. The plant itself is in the brightest position on the unit, the top or a high front edge, and only the foliage hangs through the darker volume where nothing could live. The greenery in the middle of the shelf is foliage, not a plant position, and that is the whole trick.
Is it a problem to put a pot directly above books?
It is a decision worth making on purpose. A pot of soil is a container of damp material sitting over paper, on a piece of furniture that is usually not sealed and frequently not level. That is not an argument against the idea, it is an argument for choosing which shelf you are willing to have it over and keeping it somewhere you actually look, rather than at the back of a high shelf nobody inspects.
What if my bookshelf is nowhere near a window?
Then it is a Low Light position throughout and there are three honest answers. Use the top only, with something suited to the band the top really sits in. Choose genuinely low-light plants and accept holding rather than growing. Or leave the plants out, because filling a dark interior with plants that will decline is a maintenance schedule rather than styling.
The part worth remembering
A bookshelf is a wall-facing, deep, closely spaced, full container, which is four strikes against light in one piece of furniture.
Use its edges: the top, the front, the window end. Let a trailing plant live at the top and be seen further down. And if the unit is far from any window, the honest answer is that it is a bookshelf. If you have not mapped which parts of your rooms are which, the room-by-room survey comes first.