Monthly Archives: August 2019

California Native Plants, irrigation, perennials, shrubs, watering

Make Every Drop Count:Best Watering Practices

Low water-use leucospermum or Pincushion.

Water is our most precious resource. One of the Apollo 11 astronauts recently said that the look back from the moon at our planet and blue oceans to be even more impressive than the moon itself. Life can?t exist without water. You are the steward of your own piece of planet earth. How you water can make it thrive and you can save water at the same time.

With summer water bills arriving this is a good time to re-visit how often and how much to water that landscape you?ve spent so much money to create. Basically, you?re wasting water if you water too shallow or too often. Here are some guidelines.

Photosynthesis is one of the most remarkable biochemical processes on earth and allows plants to use sunlight to make food from water and carbon dioxide. At temperatures about 104 degrees, however, the enzymes that carry out photosynthesis lose their shape and functionality. A garden that provides optimum light and water but gets too hot will be less vigorous.

California native Fremontodendron

Plants have natural systems that respond to heat problems. Plants can cool themselves by pumping water out through the leaves for a kind of swamp cooler effect. They can also make ?heat-shock? proteins which reduces problems from over heating. All these strategies can take resources away from a plant?s other needs like growth, flowering and fruiting.

So how much water do different types of plants need during the heat of summer?

Be sure that you water trees and shrubs deeply checking soil moisture first with a trowel. Established small to medium shrubs should be watered when the top 3-6″ is dry, large shrubs and trees when the top 6-12″ is dry.

As a rule of thumb, trees and large shrubs need deep but infrequent watering. They should be on a separate valve than your smaller shrubs and perennials. Water ornamental trees 1-3 times per month depending on the type and soil. Tree roots grow 12-36? deep and require 10 gallons of water per inch of trunk diameter.

Apply water with a soaker hose, drip system emitters or hand held hose with shut off and soft spray attachment according to your water district?s restrictions. Don?t dig holes in the ground in an effort to water deeply. This dries out roots even more. Be sure to water the root zone to the indicated root depth every time you water. Watering deeper than the root zone only means you are wasting water. You can test how deep you watered by pushing a thin, smooth rod into the ground soon after you irrigate. The soil probe should easily slide through the wet soil but become difficult to push when reaching dry soil.

The roots of smaller shrubs are 12-24? deep in the soil. Established native shrubs may need only monthly waterings to keep them looking their best while other shrubs may need watering every 7-10 days during the heat of the summer. Perennial roots only go down 12? or so and may need watering once or twice a week depending on type.

grevillea lanigera ‘Mt. Tamboritha’ groundcover

When is the best time to water? Watering in the morning is the most efficient whether you water by sprinkler, drip system, soaker hose or by hand. The water soaks deep in the soil without risk of evaporation. It bolsters the plant for the day and has dried from leaves by evening reducing the risk for foliar diseases like mildew. Plant roots are also more receptive to watering in the morning.

Is it true that water droplets will scorch leaves in the midday sun? According to a study, fuzzy-leaved plants hold water droplets above the leaf surface and act as a magnifying glass to the light beaming through them so there is a very slight chance of scorch. The study also reported that water droplets on smooth leaves, such as maples, cannot cause leaf burn, regardless of the time of day.

Crape myrtle, Dog Days of Summer, gardening tips, late summer to-do's

The Dog Days of Summer

A swallowtail visits a butterfly bush

Just when I thought this summer wasn?t going to be as hot as last, the weather changed. With so many different microclimates in our area, one can always find a cool spot, though. Where did the term ?Dog Days of Summer? come from?

The Romans associated the hot weather from 20 days before to 20 days after the conjunction “the dog days of summer” because it coincidentally fell at the time of year when it was very hot. This falls between July 24th and August 24th.The Old Farmer?s Almanac uses slightly different dates but the Dog Days of summer are definitely here.

The name “dog star” comes from the ancient Egyptians who called Sirius, the dog star, after their god, Osiris. His head in pictograms resembles that of a dog. When the Dog Star rises in conjunction with the sun some felt the combination of the brightest luminary of the day – the sun – and and brightest star of the night – Sirius – was responsible for the extreme heat experienced during the middle of the summertime. Since Sirius is the brightest star in the night sky it’s reasonable to guess that it adds some heat to the earth but the amount is insignificant.

We now know the heat of summer is a direct result of the earth’s tilt, but now you know? the rest of the story.

As summer rolls along you may become more aware of the different microclimates in your garden. With the drier and hotter weather some of your plants that used to get along just fine might be showing signs of stress. Taking note of these changes in the performance of your plants is what makes for a more successful landscape. When the weather cools towards the end of September you will want to move or eliminate those plants that aren?t thriving. Be sure to keep a thick layer of mulch on the soil around your plants to conserve that precious water you do allocate to each of your irrigation zones.

Deadhead flowering annuals and perennials as often as you can. Annuals like marigolds, petunias, zinnia and cosmos will stop blooming if you allow them to go to seed. The same is true of repeat blooming perennials like dahlia, scabiosa and lantana.

Lagerstroemia ‘Purple Magic’

One of my favorite plants of summer is Crape Myrtle. They bloom in the summer when we are outside more. Their fall foliage is spectacular and the bark is beautiful during the winter. Plant growers have hybridized new varieties that are more mildew resistant and smaller in size. I have my eye on a variety called Purple Magic that grows 6-10 feet tall and as wide. You can keep it as a multi-stemmed shrub or select several stems to train as a small tree. I also like Rhapsody in Pink, a slightly taller variety and Dynamite with its red flowers and orange-red fall color.

Swallowtail butterflies are regular visitors to the garden at this time of year. They especially like butterfly bush as well as zinnias and many other flowers. They are easy to photograph if you move slowly.

Fertilize shrubs lightly one last time in August or early September. All shrubs, especially broad-leaved evergreens such as rhododendron, pieris, camellia, hebe, need to calm down, stop growing and harden off to get ready for the winter cold. Some plants have already set next year’s buds.

Angel Face rose

Roses especially appreciate a bit of fertilizer now, encouraging them to bloom another round in September and October. To keep them blooming make a habit of pinching and pruning off old flowers. Always cut back to an outward facing branchlet with five leaves. There are hormones there that will cause a new rose to grow much sooner than if you cut to one with only three leaves.