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Irrigation Challenges For Residential Gardens

Here are some tips on how to water your garden the first time it is planted, the first weeks, the first year and later as well as special weather events.

Watering Mediterranean climate, low water or drought-tolerant plants

No plant is drought-tolerant when it is planted. Plants need time to develop their root systems. Deep roots is one of the features that makes plants drought-tolerant.

As a general rule, most shrubs take three years to fully establish. The common saying in the horticulture world goes as "First year they sleep, second year they creep, third year they leap" as in we will see root and width development first and height will come in later.

Always water when the soil temperature is cool. Try to water BEFORE heat waves instead of the middle of a heat wave to avoid the combination water and warmth that soil diseases like. I recommend watering at 5am as the soil has cooled and the sun has not started warming it again for the day by. (There will be another blog coming about common smart irrigation controllers if you need help deciding what to get.)

Day 1: Therefore, when any tree, shrub, groundcover or annual is planted, the first watering is critical. Water deeply to make sure that the surrounding soil is moist and the air pockets are eliminated. The best practice for months when the soil is dry would be to dig the holes first, fill the holes with water, let it drain, then re-fill hole with moistened soil that was dug up. Water again thoroughly after planting.

Week 1: Plants will need to be watered daily or every other day if there are no rains.

Week 2: If there is no heat wave, you might be able to able to reduce frequency of water to 2-3 times a week (or rain event).

Year 1: Depending on your soil, you might need to water once or twice a week. But to be more accurate, use a moisture meter and water until the moisture meter reads an 8 out of a scale of 10. Then wait to water the plants again until the moisture meter reads a 3. Do not let the soil get drier since the roots are not deep enough yet.

Year 2: Drought-tolerant plants might be able to go down to watering every other week. However, this cannot be a shallow watering. Make sure it is deep watering. On a slow, drip system, it can be over an hour of runtime.

Year 3: Most plants might be able to go down to watering once every 3 weeks. Again, deep watering is crucial.

Year 4: Once a month deep watering may be adequate, but also wash the leaves off once in a while to get the dust off as well.

This timeline works for plants that are adapted to summer-dry, winter-wet climates. Other plants might need weekly watering such as lawn grasses.

New grass lawns from sod

Lightly water the ground before installation. Since newly delivered sod is very perishable, keep the sod rolls misted while you are working the rolls out.

The first day make sure water is applied to go through the sod and the first two inches of the soil underneath since new sod does not have much of a root system yet.

For the first two weeks, to keep the sod and soil moist, water four to six times during the day for about five minutes each. Do not make the soil soggy however. If the water is standing in the soil after irrigation, it is too much water at a time.

In week three, reduce the frequency of watering (but you might need to keep the total run time the same). Check if root development is happening by tugging a corner of the sod and seeing if there is any resistance. After three weeks, once there is good root development, reduce the frequency gradually to once a day. Ideally we want deep, less frequent watering to get the roots to go deeper.

Do not water right before mowing. Let the soil firm up before cutting.

Note that CA native, lower water grasses might be able to go down to once or twice a week, deep watering as compared to conventional lawn grasses that will need 2-3 times in the minimum.

Watering new plants amongst old plants

All new plants need daily watering. When you are planting amongst established plants, the drought-tolerant plants will resent all the extra water.

Therefore, if the new plants are in the same area as the older plants, t is best if you can water the new plants by hand until the rainy season starts.

Better yet, try to wait untill rains start to do your planting if that is at all feasible.

Container Plants

Soils in containers dry out faster, especially in certain types of pots. Check the soil moisture daily in the summer. Water until soil is saturated. You can tell this by watering and stopping to see if any of the water on the top of the soil pools for at least 15 seconds or so. If the water is draining immediately, then the soil is not saturated yet.

Heat waves (mid 90s and 100 degrees F)

For lawns, mist the grass around 2pm to reduce heat by evaporation. Run the sprinklers for 1-2 minutes. This is to reduce surface temperature rather than watering the roots. This does not replace regular watering cycle. It is additional for the heat wave.

For tropicals, citrus, gardenias, non-native fuchsias, and ferns, again it is best to mist them in the middle of the day.

For CA natives and other low-water plants, it is better to look at the forecast and water plants BEFORE the heat wave hits, when the soil temperature is low. These plants (such as native oaks) do not like hot and wet at the same time since that is an environment for diseases to develop.

Frost Warning

Although it seems counter-intuitive, it is best to water the plants when you receive the frost warning to insulate the roots of the plants. If you have tropical plants, you might also have to cover them with burlap. However, try to avoid making direct contact with the leaves of the plants with the cover material by using stakes.

Additional resources on watering