You add -ed because plant is a regular verb.
-ed is added to all regular verbs to form the past tense.
This verb is regular-- just add ed to make it past tense.
The past tense of add is added.
The past tense of sort is sorted.Sort is a regular verb so you just add -ed to make the past tense = sorted.
Concentrate is a regular verb so you add -ed to make the past tense = concentrated
Yes, founded is the past tense of found (to establish).
The past tense of produce is produced. It's a regular verb so add -ed to make the past.
sift is a regular verb so add -ed to make the past. sifted
Amuse is a regular verb so add -ed to make the past tense - amused
Compressed? Just add -ed at the end to make the past tense, like for most words.
Watch is a regular verb so you add -ed to make the past tense = watched
Work is a regular verb so add -ed to make the past tense -- worked
Tail is a regular verb so add -ed to make the past tense and the past participle. tail / tailed / tailed