Seems little to do with our lives!, some of questions to investigate:

1) Picking a plum

2) Walking on grass

3) Using a hammock 

4) Riding a horse

5) Smelling a fruit on a tree

Reaping is the uprooting or severing of any living plant or vegetation from its source of growth.

This can be by uprooting an entire plant or even by breaking off a leaf or a branch.

Classic examples?

Picking an apple even though the tree remains rooted to the ground. Or picking vegetables, flowers or pulling weeds from a garden.

We are not discussing merely inhibiting growth, that is ok and not included. Eg you can close a blind near a plant even though this will block sunlight.

Some examples of how this melacha applies:

1) Removing moss from damp wood, as that's its natural growing surface. 

2) Removing seeds from a jar of water where they are sprouting.

3) Lifting a potted plant from soil.

4) Removing a non muktza seed from the ground isn't a problem as long as remained there less than 2 days as the seeds not yet began to germinate.

(Note - by dropping a seed onto the earth it's a problem immediately of sowing!)

5) Walking on grass is ok even though it may uproot grass because it's not inevitable.

6) Walking on delicate plants not ok as the stems will snap under foot, likewise heavy contact sports not simple at all. Even running on long grass an issue.

7) Deliberately kicking pollen laden dandelion not ok as the pollen will become detached.

On top of this the Rabbi's restricted 4 areas that could lead to this melacha:

1) Using a Tree:

Use includes climbing a tree, leaning against one or sitting on it. The concern was breaking off a part of the tree whilst on it. Therefore trees are muktza including even to lean one's full weight on it or even to place your jacket on it.

2) Using an animal:

The Rabbi's were concerned riding an animal could lead to this melacha as one might need a stick to prod the animal and may rip it off a tree.

3) Smelling a fruit on a tree:

Lest one come to pick it off the tree

4) Fruits that fell from a tree on Shabbos:

Are muktza.