Many annual plants, like bluebonnets and some mustards, only bloom in early spring. The majority of the 46 cactus species in the park bloom in mid to late spring. Many of these cactus species produce very large, showy flowers in varying shades of yellow, red-orange, pink, and magenta. The yuccas, including the impressive giant dagger, usually flower February–April. Many shrubs and small trees, such as the fragrant yellow huisache in the southeast part of the park, and the bright purple, fruity-smelling Texas mountain laurel also bloom in March and April. Bright, fiery-red tubular flowers emerge at the ends of the spiny, whip-like branches of ocotillo by the first of April providing nectar and pollen for hummingbirds, bees, and butterflies. The spring flowering season frequently starts in late February along the Rio Grande and proceeds upslope to the foothills of the Chisos Mountains by late April.