One of the most common causes of drooping rose bushes is simply weight. The stems are sometimes too thin to hold up the rose, especially the bud, which tends to be heavy with water. A prolific rose bush can often weigh itself down with too many buds, or suffer from dead weight after the blooms have wilted and continue to stay on the plant.
The stems of all plants depend on regular watering. The roots of the rose brush draw the water up from the soil and cycle it throughout the plant. This water fills the woody cells of the stem, giving them added strength and support to hold up the leaves and top regions of the stem. If a stem is drooping, this is one of the first warning signs that the rose needs more water. Watering frequency should be increased to solve the problem.
If the rose is getting enough water and the soil it grows in is moist, then the problem could be heat. Roses do not always do well in extremely hot climates. The heat can weaken the rose and cause it to wilt. This should be most noticeable in the leaves, but stems can droop as well when they are affected. In these conditions the rose should be moved to a shady spot, or a taller plant should be grown beside the bush to offer it shade.
A variety of bugs and spores can attack the rose, most notably the Japanese beetle and black spot. The beetles, which are about half an inch long and have shiny green backs, will eat leaves and small stems of the rose. The black spot disease will affect the rose leaves as well, giving them spreading black marks. These problems and similar ones can weaken the rose and cause it to droop. Also, weak or absent leaves on one side of the stem will weight it toward the other side, causing it to angle to the ground.
Roses can be sprayed with water or pesticides to remove Japanese beetles, aphids and other insects. Fungicides can be used to treat many different fungi diseases. Roses should also be properly pruned to control height and growth. Dead flower heads should be removed once they wilt. Fertilizers should be added to the soil in proper amounts to encourage healthy bushes.