This little cactus is so fast to knit - I designed the pattern & knitted it up in 2 days. (designing trial & error took the most time.)  You might want to make the flower in your favorite colors, or you could make several flowers to sew on the top.  I hope you have fun with this pattern.

Cactus is 3 1/2" tall.

Small amounts of worsted weight yarn:  light green, yellow & orange

Materials:  Size 7 needles
Yarn needle
Polyfill stuffing
Heavy cardboard

Gauge: 13 sts = 2"

Cactus:
  With the green yarn cast on 30 sts.  Work in K1P1 for 26 rows.  Cut yarn leaving a long end.  With yarn needle, weave through sts.  pull up tightly & secure.  With right sides together back stitch the row ends together.  Stuff firmly.  Cut a 2 1/4" diameter heavy cardboard circle & place inside cast on sts.  Weave the cast on tail through the cast on sts,  pull up tightly & secure.

Flower:
  With yellow yarn cast on 15 sts.  Work in garter st for 8 rows.  Cut the yellow yarn & join orange yarn.  Garter st 2rows.  Cut yarn leaving about 5".  With yarn needle, weave through sts,  pull up tightly & secure.  With right sides together, whipstitch the row ends together.  Weave in all ends except for the yellow cast on tail & the 5" orange end, & turn right side out.  Weave the cast on tail through the cast on sts, pull up tightly & secure.  Place the gathered cast on sts against the orange gathered sts & run the orange end through these sts to create a flat disc shape.  Sew the flower to the top of the cactus.