Planting a tree is a physical manifestation that symbolizes the growth of your relationship. Together you can see the tree grow just as your love and married life does, and you must nurture it in order to keep it alive.
So, you gather two pots of dirt, possibly from a special, significant place, and plant a tree in the combined soil. Water it together with two watering cans (perhaps, again, with water from a meaningful place), or even one shared watering can. You may even consider including your guests or immediate family and friends—ask them to add their own scatters of soil or seeds.
An Excerpt from Captain Corelli’s Mandolin by Louis de Bernières
Love is a temporary madness.
It erupts like volcanoes and then subsides.
And when it subsides, you have to make a decision.
You have to work out whether your roots have so entwined together
that it is inconceivable that you should ever part.
Because this is what love is.
Love is not breathlessness,
It is not excitement,
It is not the promulgation of eternal passion.
That is just being “in love” which any fool can do.
Love itself is what is left over when being in love has burned away,
And this is both an art and a fortunate accident.
Those that truly love, have roots that grow towards each other underground,
And when all the pretty blossom have fallen from their branches,
They find that they are one tree and not two.