verb, broadly
to be abandoned (to the point that grass has grew on the subject of discussion)
verb, Internet, Mainland-China, neologism
to long for something, especially a product
“這個限量版手辦我已經長草很長時間了，終於入手了！”
“这个限量版手办我已经长草很长时间了，终于入手了！”
“ zhè ge xiàn liàng bǎn shǒu bàn wǒ yǐ jīng zhǎng cǎo hěn cháng shí jiān le ， zhōng yú rù shǒu le ！ ” “I've been long for this limited edition figurine for a long time, and I finally got my hands on it!”
verb, literally
to grow grass
verb, Internet, Mainland-China, broadly, neologism
to have a desire to consume a piece of creative work or an entertainment media
“我一直都在長草這部美劇啊，可惜太忙了沒時間看。”
“我一直都在长草这部美剧啊，可惜太忙了没时间看。”
“ wǒ yī zhí dōu zài cháng cǎo zhè bù měi jù a ， kě xī tài máng le méi shí jiān kàn ． ” "I've always wanted to watch this American TV show, but I've just been too busy to watch it."
Examples (Wiktionary)
Mandarin
“这个限量版手办我已经长草很长时间了，终于入手了！”
“這個限量版手辦我已經長草很長時間了，終於入手了！”
“ zhè ge xiàn liàng bǎn shǒu bàn wǒ yǐ jīng zhǎng cǎo hěn cháng shí jiān le ， zhōng yú rù shǒu le ！ ”
“I've been long for this limited edition figurine for a long time, and I finally got my hands on it!”
Mandarin
“我一直都在长草这部美剧啊，可惜太忙了没时间看。”
“我一直都在長草這部美劇啊，可惜太忙了沒時間看。”
“ wǒ yī zhí dōu zài cháng cǎo zhè bù měi jù a ， kě xī tài máng le méi shí jiān kàn ． ”
"I've always wanted to watch this American TV show, but I've just been too busy to watch it."