Long e, in any position, with essentially no exceptions. The single most reliable vowel team in English.
Vowel teams
ee TEAM_EE_01
Strong rule · High reliability · Very common · Early · Reading and spelling
/iː/ long e: tree, see, green
Where Wiggler teaches it: Skill 9: Vowel Teams (Long)
Child explanation
Two e's together say /iː/ — the name of e. Tree, see, green.
The rule
Ee represents long e, /iː/, wherever it appears.
What is really going on
The most reliable vowel team in the language. The only systematic deviation is before r, where it becomes r-controlled (deer, cheer, beer), and been, which varies by accent between /biːn/ and /bɪn/.
Position in the word
Middle of a word — Reliable. For example: green, sleep, sheep, week.
End of a word — Reliable. For example: see, tree, free, three.
When this rule does not work
An r follows, making it r-controlled: deer, cheer, steer.
Made-up words that follow the rule. A child who reads these has the pattern rather than the vocabulary.
blee, shreep, fleen
Exceptions
been: been. Pronounced /bɪn/ in most American speech and /biːn/ in most British speech — an accent difference rather than an exception.
ee before r: deer, cheer, beer, steer, cheerful. R-controlled.
Contrast pairs
feet versus fed — Team versus single vowel.
see versus sea — Same sound, two spellings — homophones worth naming.
week versus weak
Decodable sentences
Three green trees are by the street.
The sheep need to sleep this week.
I can see the queen's feet.
Teacher note
Teach ee before ea. Ee is exceptionless and ea is not, and a child who has ee secure has somewhere to fall back to when ea fails. Point out the homophone pairs — see/sea, week/weak, meet/meat — as evidence that two spellings really can say one thing.