Category Archives: Horticulture Reports

January 2012: Horticulture Report

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Plectranthus ecklonii is a sub-tropical plant from Africa which can be grown outdoors in Zones 9-11, but in colder climates it’s grown as a house plant.

P. ecklonii is an attractive fast growing plant which flowers profusely the first season after planting. The plant should be pruned back hard in mid-winter after its flowering season.

P. ecklonii is easily propagated from cuttings or seed.

The best time to take cuttings is spring or summer. Cuttings should be about 7 inches to 10 inches long, keeping the top leaves. Place cuttings in a shady, but well lit area, keeping them moist as rooting is rapid. Cuttings can be rooted in sand or other appropriate cutting medium.

P. ecklonii seeds can be planted in a shallow standard seed tray in standard soil. Cover with a thin layer of sand and keep moist. Keep in a shady, but well lit environment. Germination is rapid. The seedlings can be planted in individual pots as soon as they are large enough to handle.

There are three P. ecklonii cultivars:

1. P. ecklonii ‘Medley-Wood’, which is the common garden cultivar with blue flowers

2. P. ecklonii ‘Tommy’, with white flowers

3. P. ecklonii ‘Erma’, with pink flowers

Read more here:
http://www.plantzafrica.com/plantnop/plectranecklon.htm

November: Horticulture Report

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The fall colors are still on the trees and there’s snow on the pass, but it is not too late to do some garden winterizing.

It’s time to cut perennials to the ground, clean up the debris and fertilize.

Fertilize!

You might be asking, “Why fertilize, isn’t everything going dormant?”
“Won’t fertilizer just make plants grow and get killed by the frost?”

Here are some strategies for fall fertilizing.

  • Lawns are coming back before they take a winter snooze. Fertilize them to give them strength for their winter nap and spring flush. Give them plenty of nitrogen in the fertilizer made for lawns. That means a little more mowing before you put it away for the winter.
  • Perennials are dying above ground, but it is important to feed the roots. Fertilize for next year’s growth.Fertilize the roots not the shoots.Phosphorus (the 2nd number on fertilizer boxes) is the important one. A fertilizer like 0-20-0 triple super phosphate would be good.
  • Observe Shrubs and Trees, if they are not yellowish or have undersized leaves they probably do not need fertilizer.Wait until early spring before adding a slow release nitrogen and micro nutrients.It is best to clear out dropped leaves and replace with mulch to keep the roots protected against winter freezing.
  • Bulbs being planted need some phosphorus and lots of potassium. A handful of super phosphate and kelp meal would be good to add in the hole with new bulbs.I am staying away from bone meal now as it might attract small vertebrates and deer. For established and naturalized bulbs lightly cover area with compost.

Now is the time that I think about adding natural and micro nutrients for the spring growth. Remember the plant is not dead, but slowly taking up nutrients in preparation of spring.

  • Greensand is a natural source of iron and potassium.
  • Kelp increases root absorption.
  • Hold off on cottonseed meal and alfalfa, they are nitrogen rich and should be applied in the spring.


Gena Goddard
AGC Horticulture Chair

Blackspot on Roses

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Diplocarpon Rosae is a devastating fungal disease commonly known as backspot, and this year’s wet spring followed by the hot weather created perfect conditions for this disease to thrive on our roses.

Blackspot easily spreads from plant to plant by water droplets. The fungus starts on the bottom leaves in the spring and moves its way up the plant as the season progresses. If left unchecked, this fungus can completely defoliate a rose which not only causes fewer flowers, but also reduces the roses’ ability to survive the winter.

Prevention:
Prevention, of course, is the first step toward controlling blackspot, and the first step for prevention is to buy disease-resistant plants.Keep in mind “resistance” is based on nationwide plant trials, so roses shipped to our nurseries from other states may not perform as well in our area.Consulting local rose growers and/or the Rogue Valley Rose Society can help determine which roses are considered disease-resistant for our climate. For instance, Rogue Valley Roses’ online catalog list disease resistant roses. https://www.roguevalleyroses.com

Also, an article on the OSU Extension website list roses known to be resistant to blackspot in the Pacific Northwest. Those include the hybrid tea roses: Electron, Keepsake & Las Vegas, the floribundas: Europeana, Liverpool, Echo & Play Girl, and the climbers: >Dortmund & Dublin Bay.

The American Rose Society also publishes information on which roses are susceptible to or resistant to rose diseases and you can research this information at: http://www.ars.org. They also post contact numbers for your local American Rose Society.

The next steps toward prevention are proper growing conditions and maintenance. Blackspot needs a wet environment for germination, so you can lessen wetness by providing plants with sun and airflow. Providing roses with suitable nutrients also helps reduce their susceptibility to blackspot by strengthening them.

Prune roses so air can flow among the leaves.
Plant rose bushes with plenty of space between them for air flow.
Plant roses in sunny locations so morning dew evaporates quickly.
Water early in the day, so there’s plenty of time for water to evaporate. Don’t water overhead roses, they just don’t like it!
Plant in well drained soil.
Fertilize properly.

For rose diet click here: https://ashlandorgardenclub.org//rose_diet

Control:
If you are seeing telltale black spots on your roses, then corrective steps should be taken immediately.First, cut off affected plant parts, then rake up all the fallen leaves and discard all of these in the trash in a plastic bag. Diseased leaves should never be composted because blackspot winters over on the leaves, not in the soil; therefore if you compost the leaves you will be dispersing blackspot throughout your garden next year when you spread your compost!

As stated above, air flow is important for controlling blackspot, so while cutting off affected canes, prune to increase air flow through the leaves and between plants. Diseased leaves and canes can be burned, but of course burning is often prohibited in the Rogue Valley,so first call (541) 776-7007 to see if burning is permitted, and remember you will need to obtain a burning permit from the Fire Department.

Treatments:
Sulfur is considered a natural fungicide and it’s readily available in liquid, wettable powder or in dust form. Sulfur does not kill blackspot spores, but prevents a new generation of spores from germinating, so it stops spores from adhering to new emerging leaves. To treat with sulphur, start by pruning off all the affected areas, then spray or dust ALL the leaves and canes. Repeat this treatment every 7-10 days. Sulfur washes off easily, so you will need to re-apply after it rains. Do not spray if temperatures are above 80 degrees and do not use any oil-based product within two weeks of using sulfur. These practices can damage the plant.

When roses go dormant in the fall, spray plants with a mixture of sulfur and horticultural oil. Horticultural oil mixed with sulfur should only be used when the plants are dormant. The oil helps the sulfur cling to the canes during the rainy season, plus it kills overwintering pests. Repeat spraying in the spring before new leaves appear.

Bicarbonates:
Spraying roses with a bicarbonate creates an alkaline environment on the plant which fungus can’t tolerate. This it what makes bicarbonate an effective fungicide. An old home remedy uses sodium bicarbonate (baking soda) mixed with water for treating blackspot,so baking soda has been used as a fungicide for several decades. But recent research shows baking soda is ONLY effective when combined with horticultural oil, and in due course the sodium in baking soda can build up in your soil making it toxic to all plants!

So if you treat your roses with baking soda, you should confine your spray to the plant and avoid overspray. This would help reduce the potential for sodium building up in the soil.The recommended mixture is 4 teaspoons baking soda, plus 1 tablespoons of all-season horticultural oil in a gallon of water. Mix thoroughly and spray on plants early in the morning. Repeat application every 7-10 days. Re-apply after a rain.

Other bicarbonates which can be used are ammonium bicarbonate or potassium bicarbonate. These bicarbonates have the added benefit of providing nitrogen and potassium to the soil which roses need, plus they eliminate the sodium concern. Ammonium bicarbonate has become difficult to obtain and it’s costly, but potassium bicarbonate is available online and at gardening stores. The formula for spraying potassium bicarbonate is 4 teaspoons of powder plus 1 tablespoon of all-season horticultural oil mixed into one gallon of water. Spray lightly on afflicted roses. This solution can be used for powdery mildew and other fungal diseases too, but check the manufacturer’s safe plant list before using on other plants. Spray roses every 10-14 days. Re-apply after a rain.

Warning: Repeated use of horticultural oil over several weeks can cause leaf burn or plant hytotoxicity, especially in warm weather

Organic Remedies:
There are several pre-made organic and natural fungal disease-control products on the market these days, products like Safer Brand, GreenCure, Eco-Smart, Rose Pharm and Serenade. You should consult your local supplier to determine which of these earth-friendly products works best for blackspot on roses. These pre-made products usually contain a sulfur/soap combination or a potassium bicarbonate/oil solution. Just remember even though these products are organic and/or natural they can still be hazardous if not used properly, so always follow the product label’s directions.

Neem oil:
Neem oil is made from the native Indian tree, Azadirachita indica. This oil is considered an organic product and has been gaining popularity with home gardeners.Research shows that Neem oil is successful at killing powdery mildew spores, as well as numerous insects and their eggs, but Purdue Extension reports it is less effective against blackspot. Most Neem oil products that boast blackspot prevention on roses also contain sulfur or potassium bicarbonate.

Chemical Fungicides:
Systemic fungicides are a chemical treatment and therefore they are not organic. There are many brand name systemic fungicides on the market, so consult your local nursery person for recommendations. Systemic fungicides are not sprayed on rose plants, but are mixed with water and poured into the soil. The plant then “takes up” the fungicide through the roots and up through the canes to the leaves preventing the leaves from becoming infected with blackspot.Because systemic fungicides are a preventive it is best applied at the beginning of the growing season when buds begin to swell, then re-applied every 6 weeks. Be aware that some plant specialists state over time plants can become resistant to chemical fungicides.

There are also several chemical fungicides you spray on the plants for treating blackspot on roses, and of course, these are not organic either. These fungicides are also preventative, so don’t wait until you see black spots covering your roses, start spraying your plants at the beginning of the growing season. These sprays are usually applied every two weeks, and as with all toxic chemicals, follow the label’s directions carefully. Do not spray when the weather is hot, as this can burn the leaves. In addition, plant specialists recommend you alternate your fungicides, because over time blackspot can build up a resistance to the one fungicide you’re using.

submit by, Carlotta Lucas

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References:
Rogue Valley Roses https://www.roguevalleyroses.com/

Oregon State University Extension Service
“http://extension.oregonstate.edu/gardening/”>http://extension.oregonstate.edu/gardening/
Purdue University Cooperative Extension “http://www.ag.purdue.edu/extension/Pages/default.aspx”>http://www.ag.purdue.edu/extension/Pages/default.aspx

University of Georgia Extension Service www.caes.uga.edu/extension/habersham/documents/Fungicide.pdf

1.Scott, Judy. (date unknown) Choose disease-resistant plants.
Retrieved from: extension.oregonstate.edu/gardening/node/1072
2. Janna Beckerman (9/07) Black Spot on Roses.
Retrieved from: www.ces.purdue.edu/extmedia/BP/BP-139-W.pdf

Winter Flowers

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Mahonia eurybracteata – Soft Caress Mahonia

Broadleaf evergreen shrub with bamboo-like leaves. Fast growing. Height 4 feet spreading to 3-4 feet with a rounded shape. Blooms mid-fall through mid-winter with yellow flowers forming in upright clusters in the center of the foliage. Flowers are long lasting, lightly fragrant and produce silvery-blue berries. Plant in partial shade and in a sheltered area; it’s only hardy to 0°F. USDA zones 7-11.

Fall Color

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Asters (Asteraceae)
Perennial. Asters come in a variety of colors and heights, and can provide a late-season source of pollen for bees and other pollinators. Plant in full sun. USDA All Zones.

 

Chrysanthemums
Perennial. Varieties can be daisy-like, pompons, spoons, singles, decorative, anemones and standard. Flowers range in colors from white, off-white, yellow, gold, bronze, red, burgundy, pink, lavender and purple. Plant in full sun. USDA Zones 3-9 , hardiness varies with cultivar.

Pansies (Viola tricolor)
Annual. Pansies come in a wide range of colors and are a perfect flower for the winter landscape. This plant is durable and winter-hardy. Plant in full sun or partial shade. USDA Zones 4-8.

Russian Sage (Perovskia atriplicifolia)
Herbaceous Perennial. Woody multi-stemmed plant 3 to 4 foot tall with silver-grayish leaves. Small tubular flowers bloom on tall spires in blue or lavender. Drought tolerant. Plant in full sun, it likes heat! USDA All Zones.

Heavenly Bamboo (Nadina domestica)
Evergreen or semi-deciduous shrub. Leaves turn fiery crimson in the winter and has shiny red berries. Plant in sun or shade, but leaves color better in the sun. USDA Zones 4-10.


Witch Hazel (Corylopsis)
Deciduous shrub. For winter flowers, the Witch Hazel shrubs like those at the entrance to Lithia Park, put on a glorious display in Jan/Feb. Slow growing 8 to 20 feet tall, and as wide. Fragrant flowers bloom on bare branches. Flowers in yellow, bronze, orange, red-orange, copper-red or red. Plant in full sun or part shade, protect from wind. USDA Zones 4-8.

Burning Bush (Euonymus Alatus)
Deciduous shrub. Slow growing to 15 feet tall, and as wide; it can be pruned to be maintained as a shrub. Dwarf varieties grow 6 to 8 ft. Inconspicuous flowers in the spring. Leaves turn a brilliant flaming red in the fall. Plant in full sun. USDA Zone 4-9

Japanese Barberry(Berberis thunbergii)
Deciduous shrub. Grows 4-6 feet tall with equal spread if not sheared. Flowers appear in May. Fruits are red oblong berries persisting on the plant into winter. Leaves turn attractive shades of red and orange in the fall. Plant in full sun. USDA Zones 4-8

Note: Japanese Barberry has been labeled an invasive species on the East Coast.
Please read the following for possible alternatives for Japanese Barberry: http://perrysperennials.info/articles/barberry.html

Hypericum Mystical Orange™ (Hypericum inodorum)
Deciduous shrub. Grows multi-stemmed upright spreading branches. Height 3 feet. Produces bright yellow flowers early spring to mid-summer. Forms striking orange berries which last through the fall. The berries have become a mainstay in floral arrangements. Plant in full sun. USDA Zones 5-9.

Other Mystical series: Mystical Beauty™/ pink berries, Mystical Red Star™/red berries, Mystical Black™ / black berries.

Flowering Kale (Brassica oleracea)
Annual, cool season. Attractive ruffled foliage in variations of green & white, pinks, purples, and reds. Height 18 inches. Grows well in pots, group with other winter-hardy flowers. Plant in full sun or partial shade. USDA All zones.

Calendulas
Annual. Calendulas are a very prolific, easily grown flower. Also known as “Pot Marigolds”. They can provide blooms late in the fall and early winter.

Snapdragon are also an easy to grow annual, and while most varieties are early summer bloomers, they often bloom again in cooler fall weather and provide blooms into winter.

Hardy Cyclamen
Perennial. A showy small autumn flowering hardy type of Cyclamen
USDA zones 5-7.

Helleborus (Christmas Rose) is also winter bloomers. USDA zones 4-9.
Both Hardy Cyclamen and Helleborus prefer a shady spot in the garden.

Berried bushes make a splash of color when planted in pots and one that comes to mind is the Beautyberry (Callicarpa), although be aware it will out grow its pot quickly. Plant in full sun or partial sun. USDA zones 6-10.

There are more, but this should get you thinking about fall color and winter flowers!

Gena Goddard
Mary Ann Wallace
Horticulture Committee

For more winter flower suggestions read AGC Article, “Mid-Winter Madness” :
https://ashlandorgardenclub.org//2011/02/mid-winter-madness.html

Happy Saint Patrick’s Day

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May the Luck of the Irish be with You…..Lucky Shamrocks!

Irish folklore tells that in the 5th century Saint Patrick used the shamrock to explain the Trinity to the Druids. The word shamrock is derived from the Celtic word, “trefoil”, three-leafed, or “little clover”. Trifolium repens is the small white clover that is found in lawns and is used as a green manure cover crop. The Irish consider this to be the true shamrock, and is not the same shamrocks sold in nurseries for Saint Patrick’s Day.

Nowadays, the shamrocks sold for St. Patrick’s Day are members of the Oxalidaceae family. Oxalis are bulbous fibrous- rooted perennials which readily multiply, the genus has over 500 varieties and are native to South Africa and South America. Oxalis plants have photonastic movement which means they respond to light, so on a cloudy day and at night their leaves fold down. Their delicate clover-like leaves range in color from soft green, dark green, purple or a variegated mixture of these colors. Flowers come in a variety of colors: white, cream, yellow, pink, purple or red. The most common Oxalis Shamrocks sold for St. Patrick’s Day are:

Oxalis regnelli (Lucky Shamrock):
Exposure: Indirect sun, light shade
Hardiness: Zones 6-10, anywhere indoors
Height: 6″-8″
Foliage Color: Green
Flower Color: White

Oxalis triangularis (Purple Shamrock):
Exposure: Indirect sun, light shade
Hardiness: Zones 6-10, anywhere indoors
Height: 7″-10″
Foliage Color: Purple
Flower Color: White to light pink

Oxalis deppei (Iron Cross Shamrock):
Exposure: Indirect sun, light shade
Hardiness: Zones 8-10, anywhere indoors
Height: 10″-12″
Foliage Color: Soft Green with purple cross-shaped markings
Flower Color: Rosy pink flowers

Outdoor Care: Oxalis regnelli and Oxalis triangularis are hardy in zones 6-10. There are hardier varieties that can be grown outdoors as a ground cover. These plants are invasive and considered a weed in some areas. Many people grow them as houseplants to maintain control. Pots can be set outdoors in the summer then brought indoors in the fall before frost. Plant shamrocks in 2 parts peat moss to 1 part loam to 1 part sand and grow in bright indirect sunlight. While growing fertilize weekly with a balanced fertilizer. Shamrocks require a dormant period, so let them rest when they start dying back. Restrict all watering and fertilizing. Let the leaves die back naturally and remove them only after they have all turned brown. Let the plant stay dormant for 3 to 4 weeks, then start watering and fertilizing again.

Indoor care: Keep plant in a well-lit location (east or west window) away from hot and cold drafts at temperatures of 60-70F during the day and 55-65F at night. They should be kept barely moist at all times and not allowed to stand in water as that will cause root rot. Fertilize every 2 -4 weeks with a houseplant fertilizer. After bloom, if the plant dies back, allow it to go dormant for 1-3 months. The corms should be kept cool and dry. After dormancy, repot and or divide the corms (optional). When signs of new growth emerge, begin to water, fertilize and move to a sunny spot. For most indoor-grown shamrocks this dormant period occurs 2 to 3 times a year.