Matt,

The simple answer to your question is no, there is no set time.

In fact, you haven't given us enough information to even have the foggiest notion of how often you should water. We don't know if the trees are newly planted or established. We have no idea how large the trees are. We aren't familiar with you soil or drainage. We don't know what type of drip line you are using, anything about the pressure driving the line, or how much water is being emitted. I will say that watering every other day is usually excessive for many scenarios.

If your arborvitaes are established plantings, they probably don't need any supplemental watering except maybe during significant drought. If they are fairly new plantings, you should water only after checking for proper soil moisture. When you water, you want to supply sufficient water so that the entire rootzone is watered. In between waterings, the surface of your soil should be allowed to begin drying out before you reapply water. Water deep and occasionally rather than shallow and often. If you are not very familiar with your soil's drainage, I would recommend that you do some investigative digging during and after watering to get a good idea of how much water it takes to supply sufficient moisture to your soil to a proper depth. Another thing to consider is that if the soil around your plant's root system (the rootball) is different from the surrounding soil (hopefully the native soil rather than amended backfill), the rootballs may dry out at a rate faster or slower than the surrounding soil. You need to ensure that the root system of your plant doesn't dry out, so you may need to check the moisture in the rootballs as well as the surrounding soil.

I planted them at the end of April. So they have been in about 6 weeks now. They are 4'-5' high. There are no brown spots on them just some branches are brown but I think it was just the bruising from planting them. The bottom on some of them look to be dying. Would mulch casue that if it got on the branches? I believe the drip line is rated at delivering .58 GPH. I did dig down around two of them last night and the soil was moist. I only dug down about 6 inches though and yesterday they did get watered early in the morning. So 12 hours later the soil was damp, not wet.

take a hand trowel.. and NEXT TO THE ROOT MASS ... dig down and see how your drip system is watering DEEPLY into the soil ...

guessing is useless ...

the plants MUST be watered throughout the root mass ... deeply.. and thoroughly ... and then allowed to near dry ...

simply dripping on the first couple inches .. will lead to failure...

and if you do not find out .. then you are simply guessing ...

we can go no further in providing an answer.. because we do not have your soil ... when i went drip .. in my sand... it makes a tear drop pattern as it goes into the sand ... on clay soil.. it makes more of an inverted triangle ... wide side up ... it would take me a much shorted time ... in sand ... to water DEEPLY ... than in clay ...

I WILL YELL.... the only way i learned how it all worked.. was to dig holes after one hour.. two hours.. 3 .. 4... to find out how my system worked in my soil ... [I GUESS I DIDNT YELL ...LOL]

I HAVE TWO TYPES OF DRIP.. ONE TYPE.. I RUN FOR 4 TO 6 HOURS PER ZONE.. [it provides .25 gals per hour at 8 pounds] THE OTHER ... carp ... lol ... the other type ... i can run for one hour ... because it runs at spigot pressure of 50 pounds and delivers a much higher rate, which escapes me right now ...

if you bought an engineered drip line.. you should be able to know how many gallons per hour it is delivering per emitter .... and make educated guesses.. then proven by the dug hole ...

if you just bought the cheap weep hose ... with no known drip rate.. then that is just another variable to which you will have no answer ...

dig hole.. find out..

ken

Hey Ken:

I answered the questions about the drip line and digging the hole in my previous post. Why do you find it necessary to go off about nothing after I answered that? Do you just have the need to be a horses ass on a public forum or were you just born that way?

at least its good to know i am consistent in my answers ...

you are welcome ..

ken

Wasn't doing me a favor by qeustiong things I already answered. If he took time and read my post he would have known that. Everything he wrote about I had answered previously...

mattyp- the post with your "answers" was at 8:44. Ken's was at 9:01. Given the verboseness of Ken's well put post, it's likely a case of cross-posting.

tj

It's impossible to tell someone the duration and frequency of proper irrigation. As Brandon and Ken clearly pointed out, there are too many variables involved. It sounds like a huge over-simplification but you need to water as often as the plants require and as the weather dictates, but deeply and thoroughly when you do. It is often suggested to time low emission type irrigation systems (like drips or soakers) to determine how long it takes for the water to percolate properly down through the root zone. As stated - different rates for different soils :-)

Newly planted trees and shrubs will need regular deep watering for at least the first two growing seasons and then as necessary thereafter. Even established and drought tolerant trees and shrubs may need watering attention in excessive heat and extended dry periods.