You can mulch over soaker hoses, which helps hold the water in ground.

One watering method for trees is using soaker hoses.  TreeSteward Steve Campbell shares his experiences below.

I’ve installed 100′ lengths of soaker hose under a layer of mulch, snaking it around plants in planting beds. I bring a regular hose over and hook it up to the soaker hose end. One advantage- the soaker hose will efficiently irrigate a larger area than a gator bag/ooze tube. For the soaker hose installed under mulch, (see photo above)  it is important to keep the hose fitting covered (plastic bag and a tie) to keep dirt out between uses.  To anchor the soaker hoses I bend 10 or 12 gauge galvanized wire into a “U” shape.  Also note where you’ve installed it before digging in your garden, using a plant label or good memory.  Electrical tape can be wound multiple times if a small leak develops in a hose (rare in my experience).

I use a portable, 25′ length hose in more limited situations and just lay it on the ground around the root zone, I water the trees in front of my house using a portable, 25′ length hose and just lay it on the ground around the root zone. (see photo below) I remove the hose after each watering, which is a little cumbersome but it’s worth it to have shade on the street.

A soaker hose is better for watering roots farther from the trunk. Photo by TreeSteward Steve Campbell

To determine the flow rate of a new soaker hose: I first connect a regular hose to it, put the soaker hose in a large pail, turn on the faucet for 30 seconds or one minute, then turn the water off. You can determine the flow rate by measuring the water in the bucket. The faucet position would best be turned to about the same approx. place to get a similar flow rate. I mark a spot on the faucet with tape. I myself use kitchen timers, but there are timers which connect into the water line and cut off the flow when desired. For more information google, for example, ”soaker hose tips”, or go to a site like www.savingwater.org