There are many reasons why fireplaces and their chimneys are not such a safety concern like they were decades ago. Only a few modern homes are even equipped with them. Installation of a new fireplace is outlawed in many municipalities, even if a fireplace gets damaged by an earthquake, and should be replaced. Urban sprawl has replaced almost all of the orchards and woods that once supplied affordable fuel.
Most of the few fireplaces and wood stoves that still get used are safer because their chimneys are outfitted with spark arrestors. Also, most combustible cedar roofs have been replaced by non-combustible roofing material. Nonetheless, chimneys can sometimes get overwhelmed by potentially combustible vegetation. Trees, large shrubbery and vines might need to be pruned for adequate clearance from the heat.
Vines like ivy, Boston ivy and creeping fig are sometimes allowed to climb chimneys because they do not damage bricks as easily as they damage painted surfaces. However, they can easily grow over the top of a chimney. Aggressive vines generate significant volumes of vegetation, and can accumulate even more from nearby trees. Because they are directly over chimney exhaust, they ignite as soon as a fir is lit below.
Trees that reach over chimneys take a bit more time to burn because heat dissipates somewhat in the space between the top of the chimney and the higher vegetation. Cypress, pine, eucalyptus, cedar and big junipers are very combustible. If they get close enough, ungroomed palms and yuccas can be even worse! Deciduous trees are mostly defoliated, and less combustible while it Is cool enough to use a fireplace.
Regardless, all chimneys need adequate clearance from vegetation. Trees and vines that were allowed to get too close while fireplaces were unused through summer will need to be pruned back before the first fire is lit to take the chill out of cooling autumn weather. Debris that collects behind (upslope from) chimneys should also be removed. It can be combustible while dry, and once dampened by rain, it can cause rot.
This is also a good time to start cleaning eaves-troughs (gutters) and downspouts. Yes, it may need to be done more than once if enough deciduous foliage continues to fall through autumn. Debris is easiest to clean out while dry (before it needs to be cleaned out), but unfortunately becomes messier with rain.