Plants for Clay Soil: Annuals and Bulbs

In this post I am adding annuals and bulbs to the list of plants that thrive in clay soil and partial sun, and are native/Mediterranean, drought-tolerant, and deer-tolerant. Annuals grow for one season, but often reseed themselves and return season after season. Bulbs, corms, and rhizomes typically bloom for a season, then go dormant and store up food for their next blooming cycle. In either case, this is my kind of plant! Their flowers are often showy and colorful.

Bulbs

• Colchicum (Autumn Crocus, Meadow Saffron) – 4-12 inches, with 6 inch spread. Bold pink flowers that resemble crocus, with broad strap-like leaves. Some bloom in spring, others in fall. The fall blooming types frequently grow leaves in spring. Propagates from bulbs. No summer water. Native to the Mediterranean and central Asia. Colchicaceae family (but has been reclassified to the lily family).
• Dietes (Fortnight Lily) – 2-3 feet, with 2-3 feet spread. White flowers that resemble iris, with patterns of yellow and lilac; evergreen, iris-like leaves. Grows in sun or part shade, with little to no water. Deer resistant. Native to Africa. I have several clumps of these and love their blooms. They can grow with very little water, but produce more blooms with some water. Propagates from rhizomes. Iridaceae family.
• Freesia (Freesia) – 6-12 inches, with 6 inch spread. Spikes of fragrant, tubular flowers on wiry stems, with leaves in a fan similar to iris. Hybrid flower colors range from white, to yellow, lavender, purple, pink, red, bright yellow, or orange. Propagates from corms. They like full sun, and do not need water. Native to South Africa. I have a patch of these that have reverted from strong yellow, to very pale yellow. They have a heavenly scent, and bloom with Muscari. Iridaceae family.
• Hyacinthoides hispanica, sometimes sold as Scilla campanulata (Spanish Bluebells) – they grow in clumps as the bulbs divide, with blue (sometimes white or pink) flower bells well-spaced on strong upright stems to 18 inches. Blooms in March and April, with winter sun and often after a good rain. Grows under deciduous trees and shrubs, and propagates freely from bulbs and seeds. This Mediterranean plant is native to the Iberian Peninsula. In my garden, they bloom in early spring, then dry up and disappear during the dry summer months. Asparagaceae family.
• Muscari spp. (Grape Hyacinth) – they grow in clumps as bulbs divide, with blue or white flowers that resemble hyacinth on 8-12 inch spikes, with slim, fleshy leaves. Blooms in early spring after the first rains. Full sun to part shade with winter light, no summer water. Native to Mediterranean and Asia. In my garden, they require no care. They start blooming in early February, giving hope to the winter-weary gardener! Asparagaceae family.

 Muscari

 Spanish Blue Bells

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Annuals

• Clarkia spp. (Clarkia) – 12-30 inches, with 12-18 inch spread. Pink, white, purple, or red flowers (single and double) that resemble California poppy. Small lanceolate leaves are distributed on the stems. Propagate from seed in the fall to take advantage of winter rain. Tolerates clay soil. Native to North and South America, including California. C. rubicunda (herald of summer) is from the Central Coast. Species is named after Captain William Clark, of Lewis and Clark fame. Onagraceae family.
• Gilia tricolor (Gilia, Bird's Eyes) – 6-12 inches, with 8 inch spread. Small, blue-violet flowers with five petals and pale blue pollen; and feathery palmate leaves. Blooms in spring and into summer. Propagate from seed in the fall to take advantage of winter rain. Self-sowing. Does well with occasional water. Native to western North America, including California. Polemoniaceae family.
• Lupinus microcarpus var. densiflorus (Yellow Bush Lupine, Coastal Bush Lupine) – 1-2 feet, with 1-2 feet spread. Clusters of yellow, lilac, or white flowers on tall spikes, with evergreen leaves. Blooms in spring. Does well with occasional water. Native from California to British Columbia. Fabaceae family.
• Nigella damascena (Love-in-a-Mist) – 12-18 inches, with 12 inch spread. Blue flowers and distinctive papery seed pods. Blooms in spring, and then dies back to the ground during the summer. Threadlike leaves, similar to dill. Self-sowing. My gardening buddy, Ruth, gave me seeds from her garden. No water. Native to Mediterranean. Ranunculaceae family.
• Phacelia campanularia (California Dessert Phacelia) – 6-18 inches, with 6-18 inch spread. Deep blue, bell-shaped flowers in spring, with narrow, coarsely-toothed, gray-green leaves. Flowers grow on one side of a coil-shaped stem - resembling a scorpion tail. Attracts butterflies and bees. Native to the California desert, so adapted for dry conditions (but does not like frost). Hydrophyllaceae family.

Good Sources:

• Annie’s Annuals and Perennials: http://www.anniesannuals.com/
• Las Pilitas Nursery (Santa Margarita): http://www.laspilitas.com/
• Telos Rare Bulbs: http://www.telosrarebulbs.com/

Plants for Clay Soil: Perrenials

In this post I am adding perennials to my list of plants that can thrive in clay soil, and partial sun. This is part of my quest to create a native/Mediterranean, drought-tolerant, deer-tolerant entrance to our home, with seasonal interest, low maintenance, and consideration for its Asian heritage. Perennials are herbaceous plants that live two or more years. Some die back to the ground after blooming for a period of dormancy, and then re-emerge the next season; others are evergreen throughout the year. I have included a few plants that are already growing in our planters. Most are not California natives, but they are solid performers that thrive where they are planted, on little water. Why rip them out?

• Agapanthus africanus (Lily of the Nile) – 2-3 feet tall, with 2-3 feet spread. Deep purple or white rounded flower umbels grow on 4 feet stalks, with glossy, strap-like leaves (monocots, with parallel veins). They are extremely drought tolerant, and flourish in sun or part sun. They are native to South Africa, which is home to some very tough, beautiful plants. We have quite a few Agapanthuses growing in our planters. I love their shiny leaves, and floating flower globes through the summer months. Amaryllidaceous family.



Agapanthus africanus (Lily of the Nile)

• Heuchera spp. (Coral Bells or Alum Root) – 1-2 feet, with 1-2 feet spread. White or pink flowers; leaves are basal, dark green, and somewhat hairy. Variations include H. micrantha (Crevice Heuchera), and “Martha Roderick” with pink flowers. Compatible with oak. Saxifragaceae family.
• Iris douglasiana (Douglas Iris) – 1-2 feet, with 1-2 feet spread. Colors range from pale blue, lavender, and mauve to deeper shades of blue and purple. Also in yellow, copper, cream and white. Dark green leaves, usually evergreen. Starts blooming in January or February near the coast, and continues through May. Compatible with oak. We have a patch of deep blue iris that comes back faithfully every spring. I’d like to add white. Iridaceae family. 
• Juniperus spp. (J. procumbens or J. horizontalis) – 12 inches, with 3-4 feet spread. Blue-green to green carpet. Small, white flowers in spring, and glaucous blue fruit in the fall. Drought tolerant once established, and deer tolerant. We have several of these attractive, low-growing evergreen plants in the planter area. I may decide to relocate them, or encourage growth in a new direction. Cupressaceae family.

• Lithodora diffusa  – 6 inches high, with a 2 feet spread, mat forming. Masses of deep purple, five-lobed flowers, with deep green lanceolate leaves. Summer flowering, but ours seems to bloom throughout the year. Requires well-drained soil, but is doing fine in our planter. Deer resistant. Boraginaceae family.
• Mimulus spp. (Bush Monkey Flower or Sticky Monkey Flower) – 1-3 feet, with 1-3 feet spread. Tubular flowers in shades of orange, apricot, yellow, and red. They are short-lived perennials, so need to be replaced every few years. Attracts hummingbirds. Scrophulariaceae family.
• Monardella villosa (Coyote Mint) – 1-2 feet, with 1-2 feet spread. Lavender to rose flowers that bloom July through August. Aromatic gray-green leaves. Attracts butterflies. Needs sun or part sun. Drought tolerant to moderate water in heat. Requires well-drained soil. Deer tolerant. Good for dry slopes, rock gardens, and containers. Compatible with oak. Lamiaceae family.
• Penstemon heterophyllus (Foothill Penstemon) – 1-2 feet, with 2 feet spread. Tubular flowers on spikes in many colors. Evergreen foliage along stems. Attracts humming birds. Variations include P. heterophyllus “Margarita BOP" (Bottom of the Porch) in purple, and “Blue Springs” in deep blue. Scrophulariaceae family.
• Unidentified (snapdragon?) – 1 foot, with 1 foot spread. White blossoms with traces of yellow, resembling violets. Woody stem and lanceolate, notched leaves. This is a tough, tenacious perennial that blooms through neglect and drought, despite the clay soil. I don’t know its name, but we purchased one from Annie’s Annuals in Richmond, CA five or six years ago. Possibly from the Scophulariaceae family.



Unidentified snapdragon (and tough performer)

• Unidentified (Scotch heather?) – 1 foot, with 2-3 feet spread. Tiny bell-shaped flowers on branch tips in shades of pale pink, lavender, and purple. Scale-like dark green leaves. Blooms mid-to-late summer. Requires moderate water, but thrives on little water where planted. A native of Scotland, Ireland, Russia, so may appeal to my family roots. Ericaceae family.

Good sources:

• Annie's Annuals and Perennials:  http://www.anniesannuals.com/
• California Flora Nursery (no mail order, but an hour north of Oakland/Berkeley): http://www.calfloranursery.com/  

Plants for Clay Soil: Low Shrubs

As mentioned in a previous post, I’m on a quest to create a native/Mediterranean, drought-tolerant, deer-tolerant entrance to our home, with seasonal interest, low maintenance, and consideration for the garden’s Asian flavor. In this post I have compiled a list of low shrubs that can thrive in clay soil, and partial sun. Shrubs are woody plants with multiple trunks or branches growing from the base; they range from ground covers, to almost 15 feet tall.

My selections are in the Coast Live Oak tree palette, using Bob Perry’s classification in Landscape Plants for California Gardens. In nature, they are found in close proximity, and have similar requirements. Most native plants require good drainage, and typically do not require a lot of organic amendment. Here are some favorites that meet my criteria. Some are on the fringe, but might work with careful placement.

• Arctostaphylos “Emerald Carpet” (Emerald carpet manzanita) – 12” high, with 4-6 feet spread. Pale pink, urn-shaped flowers and attractive vertical leaves. Use as a low shrub with training, or ground cover. Does not like heavy clay soil. Attracts pollinators. Requires little water once established. Compatible with oak. Ericaceae family.
• A. hookeri (Hooker manzanita) – 2-3 feet high, with 4-8 feet spread. White to pale pink urn-shaped flowers. Forms dense mounds. Attracts pollinators. Requires little water once established. Compatible with oak.

Arctostaphylus hookeri ssp. franciscana (Hooker manzanita) - photo by Stan Sheps taken at the
Regional Parks Botanic Garden, Berkeley, California, taken April 2007. Creative Commons.

• Artemesia spp. (California sagebrush) – low rounded form, 2-4 feet high, with 3-6 feet spread. Silver-gray, fine textured foliage with pungent aroma, and insignificant yellow-green flowers. Compatible with oak. Asteraceae family.
• Ceanothus maritimus “Valley Violet” (Maritime ceanothus) – low mounded form, 1-3 feet high, with a 3-8 feet spread. Pale white to pale lavender flowers from February to June (dark lavender for some cultivars). Shaping can improve appearance; prune in late summer or fall. Requires little water once established. Compatible with oak. Rhamnaceae family.



Ceanothus maritimus "Valley Violet" (Maritime ceanothus) - photographer unknown.

• Galvezia speciosa “Boca Rosa” (Island snapdragon) – 3-4 feet, with 5-7 feet spread. Scarlet, tubular flowers bloom throughout the year, especially in spring. Does not tolerate frost. Shaping can improve appearance. Scrophylariaceae family.
• Gaultheria shallon (Salal) – 1 ½ feet tall, with 4 feet spread. Pink and white urn-shaped flowers April – July, and then dark blue, edible berries. Leaves have a hint of red, and branches are deep red. Use for erosion control, ground cover, hedge, or low shrub. Requires little water once established. Attracts pollinators. Ericaceae family.
• Rhamcus california “Sea view” (California coffeeberry) – 2 feet high, with 4 feet spread. Inconspicuous flowers in spring, with showy berries. Leathery, dark leaves. Dioecious. Rhamnaceae family.
• Rhododendron occidental (Western Azalea) – 3-10 feet high, with 3-10 feet spread. Delicate white bloom, tinged with pink and orange, sweet fragrance. Sometimes fussy; prefers acidic soil, so does well with organic matter. Attracts pollinators. Prefers shade, and is riparian, so requires more water (may not be a good fit). Ericaceae family.
• Rhus ovata (Sugar bush) – 4-10 feet high, with 4-10 feet spread. Reddish fruit with sugary coating, and fire-resistant dark green leaves. Can be clipped as a hedge. Compatible with oak. Anacordiaceae family.
• Rosa californica (California rose) – 3-6 feet high, with 5 feet spread. Can be kept low by pruning right after blossoming. Large pink flowers have a rose fragrance, and bloom from spring to summer; brightly colored rose hips. Attracts pollinators. Prefers full sun near the coast, or shade inland, so place accordingly. Deer eat flowers but not the leaves. Rosaceae family.

Good sources:

• Bay Natives: http://www.baynatives.com/
• The Watershed Nursery : http://www.watershednursery.com/
• Berkeley Horticultural Nursery: http://berkeleyhort.com/index.html

 

Plants for Clay Soil

I have been threatening to redo my front planters for several years now, and never seem to get around to it. Too busy exploring the wide world of gardening to actually do some! For these two planters, I want to do more than pick up a few attractive plants from the nursery. I have a purpose – to create a native (or Mediterranean), drought-tolerant, deer-tolerant entrance to the house, with seasonal interest, low maintenance, and consideration for the garden’s historical roots.

Ceanothus spp. - I love the blue flowers of this Ceanothus that thrives down by the beach in Alameda, but the plant is five feet tall, with a 15 feet spread! It would cover both of my planters in no time. I'm on a quest for something similar but shorter. 

A previous owner of our house established the garden, working with her friend and neighbor sharing plants and ideas; and planting the maples, Chinese elm, and oak tree that are now mature. Our garden has an Asian feel to it, being under the care of a wonderful gardener who excels in “big bonsai.” I’d like to retain that feel, but start using plants that require less water than plants in the Asian palette, and that can thrive in the clay soil and partial shade of the south-facing aspect. I realize that native plants often take several years to become established, and are often picky about where they thrive, so my plan must take the long view. Plant the bones (such as shrubs and woody perennials) first, and then plant a succession of plants to fill in while they become established.

Arctostaphylos spp. - we discovered this low, shrubby Manzanita in Bryce a couple of years ago. I love the way the light filters through the upright leaves, and am searching for something similar for the Bay Area.

With these goals in mind, I will be researching several categories of plants over the next few weeks, including low shrubs, perennials (both woody and herbaceous), annuals, and bulbs. I am also looking for local nurseries that specialize in native plants that thrive in the San Francisco Bay Area. Native plants are sometimes scarce and difficult to find in stock, so Fall and Spring Plant Sales held by local botanical gardens are a good source. The upcoming San Francisco Garden Show is another good source for native plants. I will be ready, with plant lists in hand.

Plant Diseases: Wrap Up

Delve into all the things that can go wrong with your plants via diseases of all types (bacteria, parasites, water molds, nematodes, fungi, and viruses), and the built-in arms race between predator and prey that keeps balance.

Plant distortions and diseases

Getting Started

Diagnose sick plant symptoms, and figure out what to do about it.

Sick Plant Symptoms
Sick Plant Resources
Sick Plant Clinic
Back to School – Plant Diseases (Aug 2012)
Plant Diseases Update (Oct 2012)
Finished Plant Diseases! (Dec 2012)

Plant Diseases

Learn about the main categories of plant diseases, and deep dive into examples of them all.

Plant Diseases – Bacteria Fire Blight   Crown Gall
Plant Diseases – Flowering Plant Parasites Mistletoe   Lichen (not a disease)
Plant Diseases – Water Molds Downy Mildew   Sudden Oak Death
Plant Diseases – Viruses Tomato Leaf Curl Virus (TYLCV)   Grape Leafroll Associated Virus (GLRaV)
Plant Diseases – Nematodes Root Rot Nematodes   Spiral Nematodes
Plant Diseases – Fungi Black Spot of Rose (Ascomycetes)   Cedar-Apple Rust (Basidiomycetes)

Plant Diseases in Action

Head into the field to experience plant diseases all around us in the garden and nature.

SOD Blitz 2013
SODMAP App
SODBlitz Partnership
Mushrooms
Mistletoe in Bend
Clear Lake Plant Diseases
Discriminating Squirrels (Feb 2016)
Summer on the Iron Horse Trail (July 2019)

Books and Movies

Read about plant diseases and plant pathology, and enjoy films where plant diseases play a role.

Five Kingdoms
Essential Plant Pathology
All That the Rain Promises and More ...
Winter Movies 2013: Nausicaa of the Valley of the Wind
Rosemary & Thyme: And No Bird Sings (Jan 2019)

Crown Gall

Crown gall is another bacterial disease common in the San Francisco Bay Area. Crown gall is caused by the Agrobacterium tumefaciens bacteria, and is named because masses of galls grow on the roots or root crown of infected plants. Crown gall has a wide host range including 93 families of pome and stone fruits, nuts, ornamental plants, and vines and canes. It was first studied in grape vines in Italy by Fridiano Cavara in 1897. Lack of vigor and poor growth above ground, may indicate a plant is infested with crown gall below ground. You can dig carefully around the root crown to look for evidence.

The A. tumefaciens bacteria can live in soil as a saprophyte (living on nonorganic matter) for a short time, and then invades a host plant through a wound. The bacterium transfers a piece of its plasmid DNA into a plant cell; the genetic code integrates with the plant cell’s genome. Genes on the tumor-inducing (Ti) plasmid cause the cell to divide over and over, forming a tumor. The tumor, or gall, provides shelter and a food source for the bacteria, which live and multiply between the cells of the gall. When the gall deteriorates or breaks off in the soil, the bacteria are released back into the soil. Galls typically form on plant roots, but may grow above ground on trunks and stems.

Bacterial gall growing on root

Crop rotation is an important management tool to break the disease cycle. Other measures include planting crown gall resistant plants, treating the roots of transplants with A. radiobacter (an antagonistic strain), and removing infected plants. Some experts recommend disinfecting tools used for pruning and grafting, but others dispute its effectiveness. To learn more, about crown gall, visit the IPM website: http://www.ipm.ucdavis.edu/PMG/GARDEN/PLANTS/DISEASES/crowngall.html and http://www.ipm.ucdavis.edu/PMG/GARDEN/FLOWERS/DISEASE/crowngall.html.

I was fascinated to learn that this mechanism of using the Ti plasmid of A. tumefaciens to introduce genetic code into a plant’s genome is used to introduce desirable genes into plants and provides the foundation for genetic engineering. This method is used to breed plant strains that are resistant to specific diseases, accelerating the process of selective breeding that humans have been practicing since the beginning of cultivation. This is controversial for many, but lifesaving in areas of the world, like Africa, where plant diseases devastate food crops.

 

Fire Blight

One bacterial disease common in the San Francisco Bay Area is fire blight of the Rosaceae family, which attacks fruit trees, including apple, cherry, apricot, and pear. Fire blight is caused by the Erwinia amylovora bacteria. Its common name reflects that an infected tree looks scorched and blackened as though by fire. Note that bacteria are typically host-specific, so that each tree species has its own E. amylovora pathogen variation (pathovar).

This small stand of Pyrus calleryana ‘Aristocrat’ (Aristocrat Pear)
street trees in Dublin, California looks to be infected with fireblight. 

Fire blight bacteria are spread to flower buds and nectaries in early spring, in humid warm conditions, either through splashing rain or pollinators. The bacteria invade the tissue, causing the blossoms to wilt and collapse. A brown sticky exudate is produced from the damaged tissue and spreads to young shoots. The shoots become infected, blackened, and deformed in a characteristic “shepherd’s crook” shape. The bacteria overwinter in cankers that form in the bark and wood. In the spring, when the temperature and moisture levels are favorable, the cankers ooze with bacteria, and the life cycle begins again. The exudate is splashed onto nearby blossoms, or attracts pollinators, which pick up the bacteria and carry it to new blossoms.

Aristocrat pear blossoms, with fireblight symptoms	Characteristic "shepherd's crook" fireblight symptom
 Bud with symptoms of new fireblight infection	Blossoms with no apparent fireblight infection

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The best treatment is prevention, which includes planting resistant fruit trees and keeping trees healthy and vigorous to ward off infection. You can spray the tree in the spring with copper-based applications, designed to provide a barrier that prevents bacteria from reaching the blossoms, but timing is critical.  The IPM has some guidelines and references for determining the best time to spray, typically based on temperature and humidity. Several sprayings may be needed, since blossoms do not all open at once, and conditions favorable to the bacteria may persist over several months. Once infected, pruning infected limbs or branches 8-12 inches below visible injury can help stop the spread of infection. Some experts advocate sterilizing pruning equipment between cuts; others disagree.

To learn more about fire blight, visit the IPM website: http://www.ipm.ucdavis.edu/PMG/PESTNOTES/pn7414.html. You can also search the site for your specific crop: http://www.ipm.ucdavis.edu/PMG/crops-agriculture.html