At the head of the Humboldt river frosts are of almost nightly occurrence, and in the Carson Valley damaging frosts often occur in June.
Coccinea, often confounded with the red oak, but with larger leaves, with long lobes ending in several acute points; they change to a brilliant scarlet with the first October frosts, giving one of the most striking of the various glowing tints that render the American forests so beautiful in autumn.
It does not, however, prevail for long, and in the first half of September frosts begin on the middle Urals.
The young trees require protection from storms and late frosts even more than in England; the red pine of the north-eastern states, Pinus resinosa, answers well as a nurse, but the pitch pine and other species may be employed.
Throughout the region north of the Apennines no plants will thrive which cannot stand occasional severe frosts in winter, so that not only oranges and lemons but even the olive tree cannot be grown, except in specially favoured situations.