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Home > Resources> Garden Solutions > Growing Protea in California Gardens


Growing Protea in California Gardens

 

Proteas for the California Garden & How to Maintain Their Vigor
Dennis Perry
San Marcos Growers Field Day - October 2, 1998

In 1998, at the San Marcos Growers Field Day, nurseryman and protea specialist Dennis Perry gave a talk on plants in the Protea family that are good for southern California Gardens. His talk, then titled, "Growing Protea in California Gardens" covered the best cultivars and how best to grow them given our climate, soil and water limitations. Dennis made a handout for his talk. Much of the information below is from this handout but in 2003 Dennis edited this document to include additional information he has learned since and new cultivars that have become available in the subsequent 5 years. We have also linked to our database any of the plants that we continue to grow. Click on these plant names for more information and images.

Genera to be discussed and major desirable characteristics

Banksia – Exotic flowers and foliage
Leucadendron – Foliage form and color (i.e. bracts)
Leucospermum – Pincushion flowers
Protea – Exotic flowers

Genera in the Proteaceae that San Marcos Growers lists but was not discussed in this talk

Adenanthos
Grevillea
Hakea
Isopogon
Stenocarpus

Garden Maintenance

            Drainage – MORE IS BETTER
            pH – ACID IS BETTER
            Nutrition – SECONDARY & MICRONUTRIENTS
            Pruning – PRUNE, PRUNE, PRUNE
            Mulch – MULCH, MULCH, MULCH!!!
            Temperatures - Requirements vary:
                        Generally warm days & cool nights best
                        Only a few selections survive below 20 degrees Fahrenheit
            Containers – GREAT!
                        Create Drainage using Perlite & Scoria
                        Use Stable Potting Mix
                        Mineral soils
                        Long Term Organic Components
                                    Peat & Bark
                        pH - 4.5 to 5.5
                                    Add Sulfur to lower pH
                        Nutrition N,K no P! Secondary Nutrients & Micronutrients are most important

Future Trends

            Selections
            Grafting

pH, Total Alkalinity, Lime & How Much Sulfur Should I Use?


1.      Get a soil test!

2.     How much Lime (calcium carbonate & bicarbonate) is there in addition to actual pH of the soil?

3.      Usually some Lime is present, so the acid amendment, Sulfur, must:
a)     overcome the Lime in the soil to lower the pH
b)     act on the soil to lower the pH

Without Lime it takes the following, in pounds of Soil Sulfur, to effect these changes in a loam soil to a depth of 12 inches:

                                   pH                                         Soil Sulfur

                                   8.5>6.5                           11.5     #s/100 ft2
                                   8.0>6.5                             7.0     #s/100 ft2
                                   7.5>6.5                             3.7     #s/100 ft2
                                   7.0>6.5                              .7      #s/100 ft2

Gypsum should be avoided unless Calcium is not present.  Calcium along with Phosphorus can be detrimental at even ‘normal’ levels to proteas.  

Notes on Nutrition

  • Proteas feed at 1/8 - 1/4 the rates of general ornamentals.
  • Magnesium, Iron and Sulfur are the key amendments for our soils.
    Sulfur, Magnesium & Iron should be present at moderately high levels for this group of plants & exceed general plant nutrition practices
    Iron and Magnesium can be toxic so do maintain moderation.
    Magnesium is important, as important as Iron. Use epsom salts(magnesium sulfate)to amend soils
    Sulfur may take six months to alter the soil pH - both Iron Sulfate & Magnesium Sulfate can quickly drop pH.
    Iron sulfate is highly recommended.
  • Primary Plant Nutrients are usually present in adequate amounts
  • Micronutrients may be unavailable to proteas in non-acid soils, so add them
  • Gypsum should be avoided unless Calcium is not present.
  • Calcium along with Phosphorus can be detrimental at even 'normal' soil levels to Protea

    Plants Discussed at San Marcos Field Day

    Banksia integrifolia (San Marcos Growers no longer grows this plant)
    Tree with Contrasting Foliage, Yellow Flowers, 30’+x 12’ - Phytophthora Resistant, Lignotuberous, Eastern Australian species
    pH Tolerance: 8-5.0
    Nutrition: Forgiving – Moderate Feeder
    Drainage: Heavy Loam or Better
    Prune: To Shape or Ground In Late Winter
    Climate: Frost to Low 20’s F., Hot Summers w/ Cool Nights

     
    Banksia speciosa
    Easiest Western Australian Species with Serrate Foliage, Chartreuse Terminal Flowers, 20’x15’

    pH Tolerance: 7.5-5.0
    Nutrition: Forgiving – Light Feeder
    Drainage: Mounded Loam, Clay Loam Slope or Better
    Prune: To Shape or >1/2 Size In Winter
    Climate: Frost to Mid 20’s F., Warm Summers w/ Cool Nights

    Banksia spinulosa 'Schnapper Point' (Cultivar not discussed at the 1998 San Marcos Growers Field Day)

    Leucadendron argenteum
    Silver Foliage, Silver Tree - Beautiful, Difficult Can Be Short Lived (7-10 years)

    pH Tolerance: 6.3 - 5.0
    Nutrition: Light Feeder
    Drainage: Cool, Moist, Well Drained
    Prune: To Shape or >1/2 Size In Late Winter
    Climate: Light Frosts, Cool Summers, North Slopes & Coastal

     
    Leucadendron 'Cloudbank Ginny' (New Cultivar not discussed at the 1998 San Marcos Growers Field Day)

    Leucadendron floridum cv ‘Pisa’
    Silver Foliage, Silver Cones, w/Yellow Bracts February-April, 7’x4’ - Attractive Shrub, Fairly Adaptable

    pH Tolerance: 7.0-5.0
    Nutrition: Forgiving – Light Feeder
    Drainage: Mounded Sandy Loam or Better
    Prune: To Shape or >1/2 Size In Late Winter
    Climate: Frosts to Mid 20’s F., Warm Summers w/ Cool Nights

    Leucadendron galpinii
    Adaptable Selection with Silver Cones and Fine Gray Foliage 8’x 6’

    pH Tolerance: 7.8-5.0
    Nutrition: Forgiving – Light Feeder
    Drainage: Heavy Loam or Better
    Prune: To Shape or >1/2 Size In Late Winter
    Climate: Frosts to Low 20’s F., Hot Summers w/ Cool Nights, South Slopes

    Leucadendron 'Perry's Red' (Cultivar not discussed at the 1998 San Marcos Growers Field Day)

     
    Leucadendron 'Red Gem' (Cultivar not discussed at the 1998 San Marcos Growers Field Day)

    Leucadendron ‘Safari Sunset’ (salignum x laureolum)
    Vigorous, ColorfulSelection with Red Bracts August – February, 7’x5’

    pH Tolerance: 7.5-5.0
    Nutrition: Forgiving – Light Feeder
    Drainage: Mounded Loam or Better
    Prune: To Shape or >1/2 Size In Late Winter
    Climate: Frosts to Low 20’s F., Hot Summers w/ Cool Nights

     
    Leucadendron 'Safari Sunshine' (Cultivar not discussed at the 1998 San Marcos Growers Field Day)

     
    Leucadendron salignum selection (San Marcos Growers no longer grows this plant)
    Fine Foliage, Red Bracts August-February ,5’x5’ – Forgiving, Widespread Lignotuberous Species

    pH Tolerance: 8.0-5.0
    Nutrition: Forgiving – Light Feeder
    Drainage: Mounded Loam or Better
    Prune: To Shape or To Ground In Late Winter
    Climate: Frosts to Low 20’s F., Hot Summers w/ Cool Nights

     
    Leucospermum cordifolium (San Marcos Growers now grows the selections of this species noted below)
    Gray Foliage, Orange Flowers in Spring, 4’ x 6’ -  Free Flowering, Disease Resistant Selection

    pH Tolerance: 7.6-5.0
    Nutrition: Forgiving – light feeder
    Drainage: Mounded Loam – Clay Loam Slope
    Prune: To Shape After Flowering
    Climate: Flowers to Upper 20’s F, Foliage to Mid 20’s F, Hot Summers w/ Cool Roots

    Leucospermum cordifolium 'Flame Spike'
    Salmon Red Flowers

    Cultural requirements: Same as L. cordifolium
    Leucospermum cordifolium 'Red'
    Deep Red Selection – For Pots or Dry Locations
    Cultural requirements: Same as L. cordifolium (Some Disease Problems in Moist Climmates)

    Leucospermum cordifolium 'Yellow Bird'
    Yellow Sprawling Selection, Disease Resistant 4’ x 7’

    Cultural requirements: Same as L. cordifolium

     
    Leucospermum cuneiforme
    Yellow Flowered Lignotuberous Selection w/ Good pH Tolerance for the Species  - Long Bloom Period in Spring

    pH Tolerance: 7.0-5.0
    Nutrition: Forgiving, light feeder
    Drainage: Mounded Sandy Loam or Better
    Prune: To Shape or to Ground After Flowering
    Climate: Foliage to low 20’s F, Flowers to upper 20’s F.  Hot Summers w/ Cool Roots.

    Leucospermum reflexum var. luteum
    Yellow Flowered Variant of L. reflexum, Gray Small Foliage, 10’ x 6’ - Early Spring Flowering, Inland Selection

    pH Tolerance: 7.7-5.0
    Nutrition: Forgiving – light feeder
    Drainage: Mounded Sandy Loam or Better
    Prune: To Shape or > ½ Size after flowering
    Climate: Foliage to Mid 20’s F, Flowers to upper 20’s F.  Hot Summers w/ Cool Roots.

     
    Leucospermum 'Scarlet Ribbon' (L. glabrum x L. tottum) - (Cultivar not discussed at the 1998 San Marcos Growers Field Day)

     
    Leucospermum 'Veld Fire' (L. conocarpodendron? x L. glabrum)
    Long Lived Small Tree w/ Yellow on Red Spring Flowers, 12’+ x 8’ - Coastal, Compact, Slow Growing, Disease Resistant

    pH Tolerance: 7.5-5.0
    Nutrition: Forgiving, moderate feeder
    Drainage: Mounded Loam or Better
    Prune: To Shape or Lightly After Flowering
    Climate: Foliage to mid 20’s F, Flowers to low 30’s F.  Warm w/ Cool Roots.

    Protea laurifolia 'Rose Mink' (Cultivar not discussed at the 1998 San Marcos Growers Field Day)

    Protea ‘Pink Ice’
    The Easiest, Best Selection of the Genus Protea

    Flowers: Pink Flowers Fall-Spring 12’ x 12’
    pH Tolerance: 7.5-5.0
    Nutrition: Forgiving – Light Feeder
    Drainage: Mounded Loam, Clay Slopes or Better
    Prune: To Shape or >1/2 Size In Late Winter
    Climate: Frost to Mid 20’s F., Hot Summers OK w/ Cool Nights

     
    Protea 'Sylvia' (P. susannae x P. eximia) (Cultivar not discussed at the 1998 San Marcos Growers Field Day)