Watering Your Garden

Watering is one of the most meditative gardening tasks. You’re giving your plants their lifeblood while you admire, inspect, worry over, harvest from, and revel in your garden. (See our discussion of indoor watering, as well.)

Plants in our gardens need water and light and air. In a climate like ours in the Bay Area, with almost no rain from spring into fall every year, the need for watering is paramount. The end of summer may seem like a time when rain is around the corner, but with two warm months until the first soaking rains of November, you must check on the soil moisture and irrigation systems in your garden to make sure your plants continue to thrive.

Buy a hose
If you don’t have a hose that delivers water to all of your garden, get one. Consider installing an automated irrigation system. But you’ll still want a hose: for planting, showering off dusty plants, and spot-watering.

Frequency: No matter how drought-tolerant your plants, you’ll need to water your garden. Maybe not every day or every week, but you’ll want to find a rhythm that changes by the season. While fall days may be shortening, this season’s weather is sunny with low humidity: two conditions that make water demands on your plants – the sun accelerates photosynthesis, the which requires water, and dry air accelerates transpiration, a fancy word for plants’ leaves losing water through their pores.

Duration: It is best to water less frequently and more deeply. But that means watering slowly. It can take several minutes to soak even a small root ball. Automated irrigation systems’ clocks will take a little programming and then seasonal adjustment for watering duration and frequency.

Watering thoroughly at planting time and in the first couple of months afterwards is crucial. More on this below.

Soil conditions influence watering
Your soil conditions will determine how frequently you need to irrigate. Get your hands into the dirt all over your garden and make mudpies. The ones that fall apart immediately are made of sandy or gravelly soils. The ones that cling nicely together but can crumble like an unbaked cookie are made of loam or silt. The ones that are sticky, that you can really smack into a paddycake and, are, well, clay-like, are made of clay soil.

Sandy, rocky, or gravelly well-drained soils require more frequent watering to serve your garden plantings. Sticky, heavy clay soil retains moisture and thus requires less watering, but it poses two problems: It’s harder to re-wet once it’s dried out, and it can stay so soaked that it drowns the roots of your plants. Loam or silt demand less of you: less-frequent watering than sandy soils, and less worry about drowning your plants.

Watering is key at planting time and afterwards
When you plant, thoroughly soak the planting hole and then the planted rootball. (Thorough soakings and follow-up dousings are less important for planting agaves and cactus and many other succulents.) For the next couple of months, you’ll want to make sure those new plantings get a good soaking every week (depending on your soil type), or even more if it’s hot or windy.

Container plantings will require more-frequent and thorough watering. Root space is limited and potting mixes drain efficiently. Even drought-tolerant plants like olives will demand more of your attention, though the toughest succulents like Agave americana will endure long stretches of dryness.

A large plant in a small pot needs more frequent waterings than a plant with a large pot with lots of room for roots. A saucer under the pot can act as a reservoir for a few days – as long as the water in the saucer stays in contact with the drainage holes.

These plants have lowest summer water needs:
Cactus (besides jungle cactus); agaves & furcraeas; succulent euphorbias; many aloes; fall-planted California natives like ceanothus, manzanita, grasses, annuals, Guadalupe palms, iris, dudleyas, and eriogonum; many Mediterranean-climate natives planted in fall, like leucadendrons, proteas, olive, rosemary, bearded iris, banksias, Mediterranean fan palms; bulbs from Mediterranean climates like daffodils, freesias, and naked ladies

Plants that need moderate water:
Ornamental grasses; cordylines, coprosmas, phormiums, tea trees, and many other New Zealand natives; some penstemons, calylophus, pelargoniums, artemisia, kangaroo paw, crinum, and certain other perennials; echeverias, sedums, kalanchoes, and many soft succulents; pindo, windmill, and queen palms; bromeliads; many conifers; oaks

Plants that need plentiful summer water:
amboos; many palms like pygmy date, king, lady, and chamaedorea; Japanese maples, magnolias and many other deciduous trees; ferns; redwoods; many summer annuals; acorus, asarum, ligularia, and lots of other perennials

Good-looking gardens need watering, even it’s careful and parsimonious. Oh, are we repeating ourselves? It’s because one of the key causes of plant failure is watering failure, especially in the planting and establishment phase, but also in the late winter and spring when rains cease. If you’re very planful and lucky – by planting natives in the fall before a classically rainy winter, for instance – you may only need to water the first couple of weeks after planting. But that’s the laudable exception.

In some years, like 2013, winter rains do not provide enough moisture to serve newly planted Mediterranean-climate-adapted plants, including California natives. It’s important to supplement those rains with irrigation when they fail. Winter is the time of the year when these plants from the Mediterranean Basin, southwest South Africa, southern and southwest Australia, central Chile, and California must have moisture to thrive and to survive the following summer drought.

Get attentive to your soil and your plants so you can respond to your garden’s need for water. You’ll be richly rewarded.