A Guide for Watering the Newly Planted Shrubs, by Ian A.Reid
This article specifically refers to the 10 shrubs that were planted near the picnic tables in the spring of 2017. The results of the recommendations can be used for other nearby plants (shrubs) as well.
These shrubs evolved over centuries without human interference. So the question is when should humans interfere with Mother Nature?
People cannot control the amount of rain for this area or any other area. If the soil is waterlogged for an extended period, the plants die. e.g. when a reservoir is created, the trees in the reservoir die for lack of oxygen. Likewise. If the roots of shrubs are waterlogged for an extended period, the shrub dies for lack of oxygen. The other extreme condition is drought over extended periods of time. Here it takes a long time for the plants to die because through evolutionary mechanisms the plant prolongs its life. So people should only intervene with Mother Nature when the normal rainfall amounts for the area are in a deficit situation except for newly planted plants when extra water is beneficial.
So what is the normal rain fall amount for this area? For this, we find that the Environment Canada’s Macdonald – Cartier station is the closest weather station to the site where the shrubs are planted.
The Government of Canada lists the monthly precipitation data for the Macdonald – Cartier Weather station in millimetres (mm), are as follows:

Feb. 
Mar. 
April 
May 
June 
July 
Aug. 
Sept. 
Oct. 
Monthly
Precipitation (mm) 
54.3 
64.4 
74.5 
80.3 
92.8 
91.9 
85.5 
90.1 
86.1 
Average Weekly
Precipitation (mm) 
13.6 
16.1 
18.6 
20.1 
23.2 
23.0 
21.4 
22.5 
21.5 
This is how roots behave after, say, a 20 mm rainfall. Because of gravity the water table gradually lowers. As the water table lowers, the roots follow the water table down to obtain nourishment. This is the normal action of roots and this regime develops a strong deep root system. When gardeners water their plants every day, the roots stay near the surface because they have lots of water. This is not a normal situation, and the plant develops a shallow root system.
I’m going to plant a rain gauge in the middle of the newly planted shrubs. The gauge will be read Fridays of each week. If there is a water deficit compared to the normal precipitation as indicated from the table above. Water will be added to make up for the deficit. By following this regime the shrubs should develop a strong deep root system. This regime of watering to make up for any deficit is especially important during the first year after transplanting. It’s not so important in subsequent years because of the strong roots developed in the first year after transplanting. If in the second year after transplanting a mini or major drought occurs, the plants should definitely be watered to at least normal amounts of water as indicated by the table above.
Now, let’s solve a hypothetical example. The rain gauge reading on a Friday showed that there is a 5 mm deficit of rain when compared to the Macdonald – Cartier weather station. This means that 5 mm of water has to be added to each of the 10 shrubs to bring the water table up to the recommended level. Since Environment Canada lists precipitation in millimeters (mm), we’ll do the calculations in mm.
For each shrub, we must add the following amount of water by bucket or hose:
Each plant is planted within a circular area covered by mulch. This area is to be watered and we need to first determine the circle area. The area of a circle,
A, equals
Pi times the circle’s Radius,
R, squared.
Pi is a constant that is close to 3.1416. This is written
A =
Pi x
R x
R. The circle diameter was measured to be 4 feet (or 122 cm). Therefore the circle
radius is
half that (61 cm). Because rainfall is measured in millimetres convert this to 610 mm. The resulting circle area is 3.1416 x 610 mm x 610 mm = 1,700,000 mm2. We’re adding water, 5 mm in depth so the volume is 1,170,000 mm2 x 5 mm = 5,845,000 mm3 (cubic mm). Let us just say it is 5.8 million mm3. Now, 1 litre contains 1 million mm3. To determine how many litres of water are needed, take the amount needed, 5.8 million mm3, and divide it by 1,000,000 mm3/litre. Conveniently, the answer is 5.8 litres (notice, it is the same number of
litres as the number of
millions mm3). Further simplify buy rounding up 5.8 to 6 litres. The calculation indicates that 6 liters of water distributed equally within the circle has to be added to each shrub to bring the water table up to normal.
This water can be added by bucket (pail) or hose. If the water is added by a bucket, simply add 6 liters of water in the bucket and spread it carefully to each shrub.
If the water is added by hose, the hose must be calibrated first as follows:
Step 1. Choose a close by hose and stretch it out as it will be used to water the shrubs. The same configuration must be used every time the shrubs are watered to maintain the same calibration. This calculation assumes that the water pressure at the source remains constant day after day. i.e. turn the tap the same number of full turns each time, or just open it to maximum each time.
Step 2. Record the time it takes to fill, say a 20 liter bucket (pail). Any watch that can measure seconds can be used to measure the time. Let us say that with our tap opened to the maximum it took 32 seconds to get 20 litres of water.
Now, from the example above, we must calculate the time it takes to fill a 6 liter container.
The calculation: 20 liters = 32 seconds (time to fill a 20 liter pail). That is a
rate of 32 seconds per 20 litres  this is 32s/20litre = 1.6 seconds/litre. If 6 litres are needed, multiply this number by the
rate. i.e. Time to get 6 litres = 6 liters x 1.6 sec/litre = 9.6 seconds. That is pretty close to 10 seconds, so say it is 10 seconds.
If the hose has a different configuration, even a slight kink in the hose makes a difference in the calibration, than in Step 1, the hose must be recalibrated. Hopefully, a nozzle will be on the hose that will deliver a gentle shower of water on the shrub, a hose without a nozzle under high pressure could damage the area around the shrub. This kind of watering is a NONO.
I must confess that I’ll probably add a little more water to each shrub as indicated by the calculations above to take care of evaporation.
When this planting and watering regime is followed, these shrubs should thrive for their whole life span that could be for up to 50 years.
Comments are welcome.
Take care,
Ian A. Reid BSc (f) UNB ‘49
NOTES:
Conversion factors:
1 inch = 2.54 cm
1 foot = 12 inches
1 cm = 10 mm
Reference:
Government of Canada weather station at the Macdonald –Cartier International Airport
Acknowledgement:
The author wishes to thank Craig Hamm for suggestions and assistance with the final edit.