Local land spirits can be very very helpful in a retreat. Therefore it is highly recommended that you make a little offering to the land spirits. You should do this at the beginning of your "after breakfast session." Just a little thing like a beverage and some nice crackers, cheese, and fruit. You can put on it whatever you think your land spirits might like. If you are in the middle of nature you might want four plates and little saucers with little tiny beverages to offer in each of the four directions. Some may only have nature in one direction, so one plate is fine in that direction. So you can place one to four depending on your environment.
First, you need a bumpa, but if you don't have a bumpa a teapot will do. You put pure water, not distilled water but good drinking water in it with saffron if you have any. And blessed medicine if you have any. If you're using a teapot in the top of it you place a non-poisonous flower. Take off the lid and stand a non-poisonous flower in it. When it's time to use the bumpa or the teapot, you pick up the flower or your peacock feather from the top, and you sprinkle the water offering over the food offerings. Then you recite the prayers below, using a bell if you have one.
Next, you would complete the offering by taking the offerings outside to the natural place identified earlier and toss the contents of the cup and the plate up in the air towards the nature spirits. Then you would return inside with your empty cup and plate and continue with your retreat practices.
Do always and everywhere
To the supreme guide, the precious Buddha,
To the supreme protection, the precious Dharma,
To the supreme spiritual companion, the precious Sangha,
To the objects of refuge, the Three Jewels, I make offerings.
[Three Times]
To all you spirits, owners of this land and place, together with your retinue,
This offering of excellent food and drink is made.
Please perform the activity to fulfill the wishes of the yogi, master and disciple, and so that
The Teachings of Lord Buddha may flourish and spread!
May you, by the power of this offering and prayer,
In whatever place and wherever we are
Always pacify sickness poverty and conflicts
And may the Buddha’s Teachings and prosperity increase!