1 = Easy to establish - germinates quickly and produces vigorous, fast­-growing seedlings. 

2 = Average. 

3 = Difficult to establish - seeds germinate slowly or intermittently; seedlings weak or slow to develop; or species subject to shading, or other difficulties.  Species generally seeded on adverse sites (saline or very wet, for example) may be generally regarded as more difficult to establish than shown in this table, since they are rated here for performance on good sites.  Any species is apt to be difficult to establish on an adverse site.