Non-native speakers of Chinese can often get the words 长 (zhǎng) vs 长得 (zhǎngde) mixed up. Both these words are about "growing", but they have different functions. Let's look at them one by one.
长 (zhǎng): to grow, to develop
The word 长 itself means "to grow" (note that this is pronounced zhǎng, and not cháng). It can mean "to grow" as in to grow larger or, or to grow a particular feature. Let's have a look at some example sentences:
Tā zhǎnggāole wǔ gōngfēn.
She's grown five centimetres taller.
Cǎo yǐ zhǎngle gēn.
The grass has grown roots.
Shù zhǎng yèzi le.
The tree has grown leaves.
Wǒ zhǎngle dòudou.
I've got a spot. (lit. I've grown a spot.)
Notice how 长 is about growing or developing features. 长 also combines into varius words related to growth, such as 增长 (zēngzhǎng).
长得 (zhǎngde): present state of growth, to look…
长得 is used to talk about the present state of growth or something, and by extension, how something or someone looks. Adding 得 to 长 is about "the result of growth". Some example sentences:
Tā zhǎngde hěn shuài.
He's very handsome.
Tā zhǎngde bǐjiào jiēshi.
She's grown quite strong.
Tā zhǎngde hěn xiàng tā bàba.
He really looks like his dad.
Nàxiē shù zhǎng de tài gāole.
Those trees have grown too tall.
Notice how 长得 is about the result of growth or an appearance or state that has developed.
Translated from: chineseboost