以上兩句句子的意思是否分別不大？

The first sentence is correct. The comparison is between now and then. The word "now" is omitted from the sentence.
The garden appears to be much more overgrown (now) than when I was here last year.

The second sentence is making a comparison between the garden vegetation now and my hair last year (?) perhaps. The second sentence is technically correct but does not make a lot of sense unless one is trying to compare their body parts with the garden vegetation.

A bad answer chosen!

2013-05-31 23:16:17 補充：
technically? Hey! Garlic, are you a mechanic?

Don't you forget you have been jobless for years!

GRAMMATICALLY! Use this adverb for Dog's sake!
What is "doesn't make A LOT OF sense"?

2013-05-31 23:16:24 補充：
Chinglish? What is "doesn't make 1/3 sense"? LMFAO! You really should KICK YOURSELF OUT OF THIS FORUM BECAUSE YOUR PATHETIC LIFE IS A SAD CASE!

花園裡似乎更比當我去年在這裡雜草叢生。
The garden appears to be much more overgrown than when I was here last year.

花園裡似乎更比我去年在這裡雜草叢生。
The garden appears to be much more overgrown than I was here last year.

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