ARLINGTON, Va. — Hundreds of volunteers ignored cloudy skies and morning rain Monday to get their hands dirty making Arlington National Cemetery more beautiful.

Nearly 400 adults, with about 50 children, took Monday off from landscaping companies in 29 states to help beautify the grounds at the venerable cemetery.

Adults pruned and braced trees, aerated soil, and put down lime, while the children planted perennials. A local horticulturalist also was on hand to teach the children about the caterpillars and other insects they found.

Two children, Abby Bradley of Falmouth, Mass., 11, and Shelby Wanzor, 10, of Atlanta, wrote winning essays that earned them a chance to lay wreaths during a ceremony at the Tomb of the Unknown Soldier.

Abby said she was inspired to volunteer by her grandfather, a late World War II Marine veteran. He would ‘‘be excited that I’m doing this for my country, and he’ll be happy for me,’’ she said.

Michelle Mercurio flew in from Jacksonville, Fla., to help fix up the cemetery for a third time. She said her husband, Timothy B. Mercurio, served as a Marine in the Gulf War. Her second cousin, Benjamin Castiglione, served with the Navy and died in Afghanistan in Sept. 3, 2009. ‘‘I think that we need to do more for the military. More for the families and the fallen soldiers and the wounded warriors,’’ she said.

The beautification event was organized by the Professional Landcare Network.