From Bulbapedia, the community-driven Pokémon encyclopedia.
Soil is always in a soft, earthy state when not in use. When a berry is planted in soil, the spoil gets dry over time. It dries the fastest with growth mulch and the slowest with damp mulch. You may purchase mulch at the Goldenrod Flower Shop. In Diamond, Pearl, and Platinum, you plant berries in soil on the ground. You check where you've planted berries with the poketch App berry checker. In HeartGold and SoulSilver the game became more complimentary by having berry pots and bringing them every where with you as a key item. You have four berry pots in the game. To water plants, you use a spray duck or a squirt bottle. The spray duck represents a psyduck and the squirt bottle represents a squirtle.