"This plant is smaller than this tree."

Translation: यह पौधा इस पेड़ से छोटा है।

[guigarfr]

Why not इस पौधा?

[Zerenei]

Sorry, better/more correct answer: यह पौधा because पौधा does not have a postposition after it, those being को, से, पर, ने, के. Which is why it's इस पेड़ से instead of यह पेड़ से, because a postposition (से) follows the noun.

[RajSahae]

I had the two clauses reversed and was marked wrong. I thought the order was unimportant?

[dinekum]

What is difference between the इस and यह

[Jakinc12]

इस is the oblique case form of यह.

If you don't know what the oblique case is,
it is whenever there is postposition following a clause or word.

For example, खाना changes to खाने when followed by a postposition like से or में.
In this sentence "यह पेड़" changes to " इस पेड़ " because it is followed by the
postposition, से.

By the way, पेड़ does not change with the oblique case because it doesn't end with an "aa" sound. खाना changes with the oblique case because it does end with an "aa" sound.

[ph.XRG6E4]

Easy