Many people do not realize just how much rain falls from the sky in a moderate rainfall. For sake of discussion, let's consider a normal ranch house that has an attached two car garage. If the structure measures 30 feet by 66 feet and has a 2 foot roof overhang, there is 2,380 square feet of roof ready and waiting to catch rain drops.
A moderate 1 inch rainfall will generate 1,483 gallons of water on this roof. This water will hit your splash blocks and enter the soil about 30 inches away from your foundation. If your region receives 40 inches of rainfall a year, you will inject about 59,320 gallons of water into your wife's gardens. That might be a little overkill, don't you think?
French drains should be 24" deep and 6" wide
Put them on the high side of your lot to prevent neighbor's water from flooding you.
If the low end can be exposed, this is better for runoff.
Run them near soggy areas or in a U around your house if you have marshy areas
Pack the bottom soil in the drain
put in a couple of inches of 1" gravel
Put in your PVC drain pipe with the holes/slots facing down.
Fill to within 1 inch with more 1" gravel
Put sod over the top to disguise.
Widen the top 6 inches and put stepping stones instead of sod.
Use a winding path rather than right angles to make it look prettier.