Wood decks hanging over unkempt vegetation are the worst offender. Cover decks with approved fire resistant skirting or use concrete or stone patios instead. Conifers like pine, cypress, cedar and juniper are the worst offenders. Other very flammable plants include bougainvillea, pampas grass, eucalyptus, New Zealand flax, chamise and many grasses. Any plant will burn, but plants with lots of water stored in their leaves, or which contain large quantities of salts, are more resistant to fire.
Examples are succulents, oleander, myoporum, lawns and many low-growing groundcovers.
The way plants are arranged in the landscape is more important than the kind of plants you use. The Zone System uses four bands of plantings to slow an approaching fire and create defensible space. Zone 3, closer to the house, is low plants to two feet tall that burn very quickly and offer very little fuel to the fire. Zone 2 is a greenbelt of succulents and very low-growing vegetation that is reluctant to burn. Zone 1, the plantings near the house, consists of less flammable species that present a minimal risk of exploding into flames during a wildfire.