By Kate Frey
Special Contributor
In our summer-dry climate most of us have to water our gardens. The frequency ranges from several times a week in hot inland areas, to once a week in cool coastal areas, or even less frequently if we have planted very drought resistant plants. Plants that require little water are referred to as drought resistant, and gardens that feature them exclusively as xeriscapes. Plants vary greatly in their ability to withstand or evade drought and many from dry climates have developed a number of morphological and physiological strategies to aid in survival. Other factors influencing the drought resistant qualities of each garden depend on plant types, the garden’s location, weather, soil type, depth, exposure, soil organic matter content and mulch.
Plants take up water through root hairs, most of which are in the top fifteen inches of soil. Plants from desert regions like cacti and succulents often have extensive, shallow, fibrous roots to capture water from light rainfalls. Leaves are reduced to spines and water is stored in swollen leaves and stems. Spines don’t just function as deterrents to predators but serve to break up air currents and minimize transpiration (evaporation of water from plants) across the leaf surface – minimizing water loss.
Spiky Agave leaves help minimize water loss.
Hairs on plant leaves perform the same function as spines to break up air currents and limit water loss across leaves. Some plants have large noticeable hairs such as “Clary Sage”, and others are covered with fine wool like Lamb’s ears, Mulliens like Verbascum olympicum and V. bomyciferum, and French lavender (Lavandula dentata).
Annual plants from summer-dry climates avoid drought by germinating, growing, flowering and setting seed during the rainy season – dying at the end of it. Seed reserves remain dormant until rains allow germination when suitable conditions return. Most California annual wildflowers are in this category and germinate and grow during cool weather when soil is moist, and finish their lifecycles as temperatures warm and the soil dries. Exceptions are the tarweeds (Hemizonia and Madia) that follow this pattern but remain small until spring annuals die, then grow and flower when this competition for space is minimized.
California native wildflowers Gilia tricolor ‘Bird’s Eyes’, Eschscholzia californica ‘Alba’ and Nemophila menziesii “Baby Blue Eyes”.
Summer-dormant bulbs like Daffodils and Narcissus evade drought by developing large underground storage units (we call bulbs) during the rainy season to store water and carbohydrates. They weather the dry season in a dormant state. Other examples are our many native bulbs, Freesias, Sparaxis, Ixia, Squill, Tulips, Grape Hyacinth and Crocus. “Naked Ladies” grow abundant foliage during the rainy season that dies in summer. Flower stalks are sent up in summer using the large reserves contained in the huge bulbs.
Some plants have white or silver foliage to reflect light and heat. We often grow them for their strikingly colored foliage. Artemisia, Lambsears, Calocephalus brownii, Santalina, Dusty Miller, Russian Sage, Lavender, some Milkweeds, and Teucrium fruticans have beautiful silver leaves.
Plants like Manzanitas, Olives, many Oaks, Myrtle, Italian Buckthorn, Strawberry Tree, California Buckwheats (Eriogonum sp.) and others have leathery or waxy leaves with the stomata (where respiration and water transpiration occurs) recessed in the bottom of the leaf in deep stomatic crypts. Recessing the stomata in deep crypts limits transpiration. Thick, leathery leaves help reduce water loss.
Other plants have reduced leaf size to minimize water loss. Rosemary, Thyme, Lavender, Olives, Broom, Junipers and Teucrium are examples. These plants may grow slowly due to reduced leaf area for photosynthesis.
Leaves on plants like some Manzanitas turn parallel to the sun to avoid solar interception.
Resinous oils found on the foliage of plants like Sage, Lavender, and Rosemary acts not just to deter animals that eat plants, but these oils evaporate on very hot days and cool plants. These are the resinous odors so apparent to us on warm afternoons.
Some plants drop a portion of their lower leaves as the weather warms. The ground under Madrone trees (Arbutus menziesii) may be littered with dried leaves, though the trees themselves are lush and green. Other plants such as Jerusalem Sage (Phlomis) have juvenile leaves that are shed as the season progresses.
California buckeye (Aesculus californica) and California polypody fern (Polypodium californicum) are drought deciduous and go completely dormant in summer even with regular water.
The Olive tree and many Manzanitas combine the strategies of silver foliage, reduced leaf size, and leathery leaves to resist drought. Lavender plants combine reduced leaf size, silver, and wooly foliage plus resinous oils to resist it. What other examples do you see in your garden?
Soil type is a big factor in developing watering schedules. As sandy soils have large pores and high porosity, water moves through these soils quickly and is not retained. Increasing the organic matter content by either incorporating compost and/or mulching with it increases the water holding capacity of sandy soils tremendously. Clay soil particles are tiny and evenly dispersed. These soils have a high water holding capacity, and poor drainage. Incorporating compost and gypsum helps these soils to aggregate so water will penetrate more easily and be held in the soil in beneficial quantities and ratios with air (oxygen), necessary for plant roots and soil micro and macroorganisms. Mulch will also increase porosity in soils over time. Make sure to use compost or composted greenwaste/manures rather than woodchips. Woodchips rob the soil of nitrogen as they break down. Loam soils generally have good water holding capacity, but this is also helped by compost. Compost is a key factor in developing soils that aid in your plants ability to resist drought.
These themes and much other practical information designed to help you create successful, healthy beautiful gardens is what we are teaching at our new garden school – The American Garden School.
The American Garden School was created to address a growing need in the U.S. for quality garden education. Many of us do not have the time or desire to commit to a formal series of horticulture-based classes at a university, yet wish to gain quality education to better our landscapes, convert our lawns, or develop a kitchen garden.
Our goal is to be the go-to garden school for comprehensive, quality, tested and fun garden education for homeowners, garden enthusiasts, landscape practitioners, school gardens and very small farmers. Our courses are designed to help you generate a successful and beautiful garden, with themes pertinent to the West such as drought tolerance, ecology, sustainable practices, and time saving. We believe in systems, efficiency, technology, science based practices, and most importantly, that a garden should bring you joy.
These intensive courses are a remarkable opportunity to learn practical and tested methods for creating successful gardens. Two-time Chelsea Flower Show gold medal winner, educator and renowned horticulturist and designer Kate Frey and local landscape manager and designer, Christa Moné, will share their expertise developed over many years in Northern California and internationally. Kate and Christa bring a wealth of information in educating people on how to create gardens that are remarkably beautiful, healthy, productive, creative and efficient to care for.
Upcoming Classes:
THE EDIBLE GARDEN-FALL/WINTER
@ CORNERSTONE SONOMA
SEPTEMBER 28, 2017
9:30AM-12:30PM
This ain’t your grandma’s veggie garden! We want to raise the bar on the concept of how we plan and plant our edible gardens, and show you that they can be just as beautiful as any other- and filled with delicious things to eat all year round!
Whether you like precise rows, or an impressionistic composition of verdant plants, this intensive, practical course will get you on the right track with simple principles and techniques to consistently generate a multitude of healthy, delicious vegetables (and flowers!). Seasonal focus will be fall and winter.
FALL OPEN GARDEN DAY & WORKSHOP
@ KATE FREY’S GARDEN
OCTOBER 7, 2017
HOPLAND,CA
Back by popular demand! Please join us for this great opportunity to see the principles and practices of The American Garden School expressed and demonstrated in Kate and her husband, Ben’s unique experiential and flower-filled garden in scenic Hopland, inland Mendocino county this fall.
Profusely planted, full of flowers, bees, bird song, and rustic structures created from wood Ben has resuscitated, it has many unique seating areas, and places to explore. Visitors call it an instant sanctuary. It is eight years old and is composed of native plants and habitat plants that attract and support a wide variety of insects and birds as well as delighting our senses. There is a vegetable garden, many rustic structures, a hermit’s hut, chicken palace (with the cutest chickens ever), bar, wood library, Swiss Chalet house, and whimsical gateposts. Surprises abound! Bring a lunch!
The Workshop will cover design, site preparation, building health soil, weed control, bees and wildlife in the garden, plant care, and will look at some great plant varieties. It will end with an irrigation system demonstration.
The Open Garden is available for people to wander and enjoy the unique and relaxing spaces of the garden.
PRACTICAL SOILS & IRRIGATION
@ CORNERSTONE SONOMA
OCTOBER 20, 2017
9:30AM-12:30PM
Why do so many plants and gardens fail to thrive despite our best efforts and intentions? Soil health and irrigation are too often overlooked in our garden planning and maintenance, and can feel overwhelming to take on. Healthy soil creates healthy plants, yet what is healthy soil and how do we create it? Irrigation is essential to any garden or landscape, but how does it all work? Do we till, or can we choose not to? Different plant categories such as vegetables, annuals, perennials, shrubs, and trees each require different approaches to soil development and watering.
Design Intensive
@ CORNERSTONE SONOMA
November 6, 2017
10:00AM-2:30PM
Details will follow soon! Please Check website
Contact us: https://americangardenschool.com/contact/
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