Beanstalk Giant's power and toughness are each equal to the number of lands you control.
Search your library for a basic land card, put it onto the battlefield, then shuffle. (Then exile this card. You may cast the creature later from exile.)
* /
*
{1}{G}
Dawntreader Elk
Creature - Elk
{G}, Sacrifice Dawntreader Elk: Search your library for a basic land card, put it onto the battlefield tapped, then shuffle.
2 /
2
{3}{G}
Ondu Giant
Creature - Giant Druid
When Ondu Giant enters the battlefield, you may search your library for a basic land card, put it onto the battlefield tapped, then shuffle.
2 /
4
{1}{G}
Primal Druid
Creature - Human Druid
When Primal Druid dies, you may search your library for a basic land card, put it onto the battlefield tapped, then shuffle.
0 /
3
{1}{G}
Viridian Emissary
Creature - Phyrexian Elf Scout
When Viridian Emissary dies, you may search your library for a basic land card, put it onto the battlefield tapped, then shuffle.