For the prefix, use the day you were born on. For the suffix, use the month. If you're not comfortable sharing your birthday, use a random date— today's date, holiday, etc.

Prefix:
1. Fern
2. Leaf
3. Bramble
4. Bracken
5. Sorrel
6. Flower
7. Clover
8. Tree
9. Laurel
10. Shrub
11. Bush
12. Holly
13. Briar
14. Moss(y)
15. Cactus
16. Mint
17. Burdock
18. Heather
19. Berry
20. Olive
21. Wheat
22. Pepper
23. Grass
24. Acorn
25. Bamboo
26. Burr
27. Cabbage
28. Cherry
29. Nettle
30. Dock
31. Thistle

Suffix:
January: claw
February: thorn
March: feather
April: whisker
May: tail
June: blossom
July: fall
August: shade
September: leaf
October: frost
November: flower
December: petal

I got Flowerfall.