Stella Otto: The Backyard Fruit Gardener

Today's Tip: Mow vegetation short around the base of fruit trees and bushes to reduce winter habitat for rodents.

An Inch a Week — How Much Water is That Really?

The rule of thumb says estab­lished fruit trees or berry bushes will need an inch of water a week. How do you mea­sure that? More impor­tantly how do you know your plants are get­ting that?

Of course, rain­fall is the nat­ural source. Typ­i­cally, ball park fig­ures assume light rain­fall is less than 0.10 inches of rain per hour. Mod­er­ate rain­fall will pro­vide between 0.10 to 0.30 inches of rain per hour. Heavy rain­fall is con­sid­ered over 0.30 inches of rain per hour. A  rain gauge is cal­i­brated to accu­rately tell you how much water accu­mu­lated dur­ing a rain shower.
When rain falls short of pro­vid­ing for your plants, you will need to sup­ple­ment the nat­ural rain­fall to the extent of the short­fall. In many areas, sum­mer may bring weeks of no rain­fall; in which case you will have to pro­vide all the needed water.
An inch of rain is pre­cisely that, water that cov­ers a given area to the depth of 1 inch. One square yard requires 4.7 or roughly 5 gal­lons of water to be cov­ered 1 inch deep. The sur­face area cov­ered by a small blue­berry or cur­rant bush could be roughly a square yard — 3 feet by 3 feet. A dwarf fruit tree might occupy more area, say 5 feet by 5 feet; 25 square feet or roughly 3 square yards. So, fig­ure that your tree would need 3 times as much or 15 gal­lons of water.
One way to sup­ply the nec­es­sary amount of water to your fruit would be via bucket; gen­tly pour­ing the equiv­a­lent of one or more 5 gal­lon buck­ets gen­tly around the root area and allow­ing it to drain into the soil. This method can require lots of heavy lift­ing and get old in a hurry if your fruit gar­den is exten­sive.
An alter­na­tive is to pro­vide water from a gen­tly trick­ling hose. To mea­sure what your hose is providing:

  1. Turn your hose on to a gen­tle trickle. Make a note of the rate of flow of your hose. Did you give the faucet a half turn, a full turn or what­ever cre­ates a gen­tle trickle?
  2. Using the hose and noz­zle set­ting that you will use for water­ing, fill a 5 gal­lon bucket, tim­ing how long it takes to fill the bucket.
  3. Now the math is sim­ple. If it took 2 min­utes to fill the bucket, it will take 2 min­utes at the same set­ting to pro­vide 5 gal­lons of water to a small bush. Water­ing your fruit tree will take 3 times that — 6 min­utes — to pro­vide 15 gallons.

You can pro­vide the water in sev­eral doses over the week or all in one dose. For deeper rooted trees and shrubs, one good deep soak­ing is bet­ter. It will encour­age growth of a deep root sys­tem that is more able to find mois­ture when the soil sur­face becomes dry. Nat­u­rally shal­low rooted bushes, such as blue­ber­ries, may do bet­ter with split appli­ca­tions of water that stay closer to the sur­face.
In extreme heat or drought, if may be appro­pri­ate to dou­ble the amount of water given to your gar­den since the plants may tran­spire more.

©2013. Adapted from the Back­yard Orchardist: A com­plete guide to grow­ing fruit trees in the home gar­den by Stella Otto.