---

All answers having "Spiny plant" as clue:

3 Character Answers:

---

RUE



4 Character Answers:

---

ALOE



5 Character Answers:

---

GORSE

NADIR

YEARN



6 Character Answers:

---

CACTUS

NETTLE



7 Character Answers:

---

INDEPTH

NEPTUNE



8 Character Answers:

---

ACANTHUS