There is no right or wrong, says Kleijn. It is important that all trees need water, he says. “Preferably put a saucer under the tree, if a little water comes out you know you have enough,” says Kooijman. For trees without a root ball, he recommends: “Cut off a small slice from the bottom, then the tree will still absorb water.” The tree is just like a bunch of flowers, you also cut off a piece when you put them in water.