Materials Needed:

Worsted weight yarn in green (or your desired tree color)
Small amounts of yarn in various colors for decorations (red, yellow, blue, etc.)
Crochet hook suitable for your yarn (size G/4.00mm works well with worsted weight yarn)
Yarn needle
Scissors
Fiberfill or stuffing of your choice
Abbreviations:

ch: chain
st: stitch
sc: single crochet
inc: increase (work 2 sc in the same stitch)
dec: decrease (single crochet 2 stitches together)
sl st: slip stitch
Pattern:

Tree:
Start with green yarn.

Magic ring, 6 sc into the ring. (6 stitches)
Inc in each st around. (12 stitches)
Sc, inc around. (18 stitches)
Sc 2, inc around. (24 stitches)
Sc 3, inc around. (30 stitches)
Sc 4, inc around. (36 stitches)
Sc 5, inc around. (42 stitches)
8-15. Sc in each st around. (42 stitches)
Sc 5, dec around. (36 stitches)
Sc 4, dec around. (30 stitches)
Sc 3, dec around. (24 stitches)
Sc 2, dec around. (18 stitches)
Sc, dec around. (12 stitches)
Stuff the tree firmly with fiberfill or stuffing.
Dec around. (6 stitches)
Fasten off and weave in the end.
Decorations:
You can make various decorations to sew onto the tree. Here are some simple shapes you can crochet:

Star:
Using yellow or gold yarn:

Magic ring, ch 1, 5 sc into the ring. (5 stitches)
Sl st into the first sc to close the round.
Fasten off and leave a long tail for sewing.
Ball Ornament:
Using red or any other color:

Magic ring, 6 sc into the ring. (6 stitches)
Sl st into the first sc to close the round.
Fasten off and leave a long tail for sewing.

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