A Garden Watering Guide for California Native Plants

Use this garden watering guide for your California native plants adapted to a dry summer climate. Such plants must not be given supplemental summer water after they are established. If you water them, THEY WILL DIE. Natives have a reputation for being difficult to grow in the garden, and summer watering is usually the reason they fail.

Good-intentioned gardeners, mostly veterans familiar with plants from Europe and Eastern United States are conditioned to water their gardens during the dry and hot summers. Immigrants brought plants from their native lands to be reminded of home. The bad reputation for natives was built up over time when California native plants adapted to a summer dry climate were mixed in with plants that required summer water. Upon supplemental watering, the exotics survived and the natives died.

The exception to the no summer water for natives rule is for those plants that are adapted to tolerate higher moisture levels in the summer. This applies to the aquatic plants, the riparian, the redwood, and the evergreen forest community plants.

For the other types of native plants, the problem with summer water is the growth of fungi in the soil that thrive in the presence of moisture and heat. These fungi affect the native plant's roots, slowly killing the plant. The reason these fungi do not affect most exotics is because the exotics evolved in a different soil ecology and they are adapted to and affected by different fungi that are not the same as Californian soil fungi. In fact, over time, the soil ecology changes to adapt to the exotics, causing more chaos to natives that require the beneficial micro-organisms in the soil. To learn more about soil ecology and soil biology, look in our resources webpage.

When choosing your plant design pay special attention to whether your lawn replanting area could be getting water from a neighbor's sprinkler or a spring uphill of this location. Check the moisture level of the soil in the summer by digging down a few inches or use a moisture meter to check the soil's condition. Moisture meters are available in garden stores and a good one should cost about $15-$30. This is well worth the price if you consider the cost of plants that can be saved by using one. And remember to come back to this guide to watering to help establish your natives.

In my yard I found that the soil next to the fence on one side stayed moist all summer from the sprinklers on the neighbor's side. I have D.G. (decomposed granite) at this location, and wanted to plant a Ceanothus 'Celestial Blue' that thrives in D.G., but the summer water would have been fatal to the Ceanothus. So I made a planting pocket with soil and put in an edible (non-native) fruit tree, Feijoa Sellowiana (Pineapple Guava). Although the Feijoa is drought tolerant, it does okay because the top of the tree gets the really hot (and bad) late afternoon sun in the summer. The extra water allows it to effectively combat this heat. And as an added bonus, thanks to the fence, the crown stays nice and dry. And if the sprinklers ever stop, since this tree is drought tolerant, it should do just fine, I reckon.

Pick the right plants, plant them with a little care, establish them with the right amount of water for the first one or two summers, weed around them, and then ignore them. This is the preferred treatment for most native plants. And neglect is so important that we will be repeating this mantra many times, so please bear with us.

How to Establish Your Young Plants

  1. After mulching, give each planting hole a good soaking with a hose.

  2. To establish deep roots, each watering session must allow for a deep soaking of the soil. Use a slow flow of water and for a longer period of time. For example, a low-volume overhead sprinkler or soaker hose for 6 to 12 hours might be appropriate.

    If you are watering by hand, set the water flow to somewhere between slow and medium, that is, adjust to allow the soil to absorb the water and prevent run-off. Then direct the hose at least 8" away from the crown, go further away as the plant grows larger.

    Water in a circle by walking around, or moving the hose every 15 minutes, and ensuring that all sides of the plant and its roots are well soaked. (And this is the reason that drip irrigation is usually not very compatible with native plants, a soaker hose wrapped around works a lot better). It may take an hour to water one plant, so I usually get an easy chair and a good book and settle down to read my favorite author. Alternately, if I am busy in the house, I set my kitchen timer and run out to change the position every 15 minutes.

    When the visible upper part of the plant is still very small the roots are growing and getting deeper, so don't compromise now. You can look forward to the fact that you won't need to do this very often, and not at all after the second summer. Another technique I use when I have a lot of young plants is to stagger the watering across my garden so that I water the front, sides, and back on different weekends so that at the end of 4 weeks, the cycle may start again or not as the weather dictates.

  3. During the first summer, the young plants will need water about once a week. Water sooner if they start to show signs of stress. Stressful conditions can be caused for example by exposure to late afternoon sun, reflected heat from concrete or stone, exposure to drying winds, not enough mulch, etc. Buy yourself a water meter and check often if you suspect your plants may be subject to conditions such as these. Signs of stress include drooping leaves, leaves turning yellow, and eventually dropping off.

  4. During the first fall and winter if rainfall is scant, the plants will need supplemental water. California native plants are accustomed to winter rain and they grow in the winter, so provide some water if natural rainfall is low. Watering about once a month is probably sufficient.

    For example, during the early dry weather of winter of 2008-2009 I watered twice, once in November, and a second time at the end of December since I had young plants that had gone in the ground in September. I have clay soil, which is excellent at moisture retention and about 3" of bark mulch.

  5. During the second Spring, provide deep supplemental water about once a month as the rains ease off and stop, for example, once end of March and then again end of April. Always check under the mulch to see how wet the soil seems before watering. Hold off watering if the top few inches of the soil seems moist.

  6. During the second summer, you should ease off from weekly watering to toughen up the plant and to get it used to drought. It continues to be super important that each watering session be deep to allow for the plant to establish deep roots. Water to keep the plant alive rather than to see extra growth. Be alert to the beginning signs of stress in the plant and water accordingly.

  7. The second fall and winter, observe and water only if the expected rainfall is low. You should not have to water more than once a month. This second growing season should help the plant establish even deeper roots, allowing it to prepare for the 20 or so years of dry summers ahead.

Watering Your Established Plant

Most plants are well established by the time they have gone through two summers and two winters with this garden watering guide to establish deep roots. After this period the plants should need no supplemental watering during summer. In the winter, if the rains completely fail, then continue to provide some water once a month or so to keep the plant healthy so that it can survive the coming summer handily. Some natives will go dormant earlier in the summer if they experience a drier than usual winter.

The plants will benefit from the dust being washed off their leaves in the dry summer months. So take a hose, walk around your garden and wash off the leaves when they look dusty, about once or twice a month. Do not do this more frequently, we mean the washing, not the walking. This keeps the leaves looking clean and green and those natives you planted will live for 20-30 years whether you want them to or not.

During the summer months, if a California native plant looks dead, then most likely it is dormant and it will start budding and growing again with the first rains. Check the description of the plant to understand what is normal for each plant in the summer. And do remember that many plants are topsy-turvy in California, they are adapted to grow in the winter and go dormant in the summer, unlike the plants from colder climate zones.

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