Learn Italian: Mi piacciono le tue trecce lunghe.

This follows the rule for feminine nouns ending in unstressed -cia or -gia. If the ending is preceded by a consonant (like the second c in treccia), the i is dropped in the plural. So, treccia becomes trecce. If the ending were preceded by a vowel, like in camicia (shirt), it would keep the i and become camicie.

Why does the adjective lunghe have an h in it?

The singular feminine form is lunga (long). When feminine adjectives ending in -ga or -ca become plural, we add an h to make them -ghe or -che. This keeps the hard g sound the same as in the singular. Without the h, the letters ge would make a soft sound, like in the English word 'gem'.

Why do we use piacciono here instead of piace?

Remember that piacere (to like) works backward compared to English. Literally, this sentence means 'Your long braids are pleasing to me.' Because the subject doing the pleasing (le tue trecce) is plural, the verb must also be the plural form piacciono.