>Two rows are available from the beginning for players to plant their Berries in, with each row containing spaces for three Berries. Diglett will dig additional rows when the player obtains a certain number of Dream Points. Currently, players can have up to ten rows.
*Rows / Dream Points
2/ Default
3/ 900
4/ 2,100
5/ 3,500
6/ ??? (10,000?)
7/ ???
8/ ???
9/ ???
10/ ??? (100,000?)**
Source
Its currently unknown. But there have been estimates.
Rows / Lowest Seen / Estimate
6 / 11,480 / 10,000
7 / 24,190 / 20,000
8 / 34,000 / 30,000
9 / 69,130 / 50,000
10 / 121,950 /100,000 -Source 2