How to Grow Roses in Your Garden?
Roses have always added beauty and it to gardening, and in 1986 the rose became the official national floral emblem in the United States. For the most enjoyment, the following tips are offered.
PLANTING
Select a site that gets good air circulation and at least 5 to 6 hours of sun. Dig a hole 24″ wide and 18″ to 24″ deep, amending the soil from the hole with generous quantities of organic materials such as garden compost, shredded fir bark mulch, or redwood soil conditioner. Put back enough of the amended soil so that the soil level in the pot will sit slightly above ground level on the outside. For rose in a FIBER POT, make holes in the sides and bottom of the pot.
Place the pot in the hole and fill in the remaining soil mixture in the sides and tamp into place. (The only difference for a rose in PLASTIC POT is to remove the pot immediately before planting. Build a tall basin around the rose, about 20″ to 24″ in diameter.
Place a 2″ to 3″ of organic mulch on top of the soil, but leave at least a 1” gap around the stem. This helps to keep the soil from crusting and aids in water penetration. (Avoid using peat moss as a mulch on top of the soil as it can pack and repel water.) Make sure that the graft is above the ground when planted. The water rose immediately. Fill them to the brim!
WATERING, FERTILIZING AND PROMOTING FLOWERS
Roses need regular, deep irrigation. Vary watering frequency according to the weather and soil conditions as well as the maturity of the plant. The best time to water is in the morning. Soaker hoses and bubbler systems work well. Always be sure to fill the basin each time you water.
For maximum flower production, roses should be fed throughout the growing season with a well-balanced, high nitrogen content fertilizer about every 4 weeks. To promote new flower buds, remove all spent blossoms. When cutting, be sure to cut the stems 1/4” above an outside leaf with at least five leaflets.
PRUNING TOOLS
The tools used most often are heavy-duty hook and blade type shears, hook & blade type Toppers, and fine-toothed, curved pruning saws. Wearing heavy-duty gloves will protect your hands. Avoid tools that have anvil type blades as they can crush and shred the canes. To ensure clean and even cuts, the blades should always be sharp. The best choice is to select shears that have replaceable parts. For difficult to reach interior growth, a keyhole saw may also prove useful.
PRUNING BUSH AND TREE ROSES
January is usually the best time of year to prune bush and tree roses. Remove any dead, damaged, or extremely weak growth. Also, remove any branches which cross another branch or which pass through the center of the bush. Encourage vigorous new growth by removing some of the oldest canes each year. When removing a cane, be certain to cut it flush with the bud union.
Cut back remaining bush by 1/3 to 1/2 of the height of the bush, being careful to make the cuts 1/4 ” above an outside facing bud. Tree roses are also pruned this way but above the top bud union. Seal pruning cuts with Seal & Heal. One time blooming varieties should not be pruned until the plant has finished flowering for the season.
TRAINING CLIMBING ROSES
Except for the removal of dead, dying, damaged, diseased and/or crossing canes or extremely weak twiggy growth, climbers should not be pruned at all during the first two to three years. During the third year, retain only 3 or 4 vigorous young canes, and lightly shorten them to force lateral branches.
Since some climbers flower on laterals formed on two to three-year-old wood, ask a salesperson for the appropriate pruning season for each variety. Seal pruning cuts with Seal & Heal. Avoid using tar-like compounds. Tying the main canes to a fan shape will direct the lateral cane to grow vertically which will flower.
DORMANT SPRAYING AND CLEAN-UP
Each January, any remaining leaves on rose bushes, rose trees, and climbers should be stripped off and discarded, not composted. Clean up all leaves and debris from the surrounding soil. Spray the entire area – plants and soil – with Disease Control.
DISEASES
The most common diseases are powdery mildew, rust, and black spot. Either Funginex or Orthenex can be used to provide effective control. Downy mildew can be treated with Aliette.
MOST COMMON PESTS
Aphids and spider mites can be controlled with contact sprays such as Natures Pest Fighter or systemic sprays such as Orthene. Fertilizers that contain systemic insecticides need to be reapplied frequently and are not as effective in cool weather… Cane borers can be controlled by sealing the ends of cut canes before eggs are deposited.
Seal & Heal works very well. Hoplia beetles are often found on light-colored flowers for several weeks in spring. These can be controlled with Orthene. Thrip damage can cause the blackening of the outer petals and prevent buds from opening. Use Orthene.
Disease and Pest Management in Roses
A 5-acre garden on the University of California at Davis campus holds 400 of the most commercially important rose varieties. Researchers are maintaining these plants as samples that are tested and shown to be disease-free. Some rose varieties can carry the rose mosaic virus without showing symptoms. In the past, some rose stock has even failed to show disease symptoms in the temperate California climate but has later shown rose mosaic symptoms after being shipped to the eastern United States.
“We do a bioassay of these plants by grafting a bud onto an indicator variety and growing it for two years to make sure symptoms do not show up,” says Mike Cunningham, rose program manager at Foundation Plant Services. Cunningham made his remarks to rose experts from around the world as they toured highlights of California’s floriculture industry following the recent Fourth International Symposium on Rose Research and Cultivation held in Santa Barbara, California, United States.
Before looking at rose research facilities at the University of California at Davis, tour participants also visited the new potted rose program at Greenheart Nursery in Arroyo Grande, the Fioli Gardens in San Francisco, Rose Gene Technology in Watsonville and the ha of hydroponic roses a few miles away from Rose Gene Technology at California Pajarosa Floral.
In addition to their 2-ha repository of disease-free roses, University of California Foundation Plant Services researchers do extensive research to learn how important diseases like rose mosaic virus are transmitted.\”We think that rose mosaic virus is transmitted among the roots of the plants,” said Deborah Golino, director of Foundation Plant Services at the University of California at Davis.
To test this theory, researchers are growing one healthy plant and a second virus-infected plant together in the same opt. The healthy plant will presumably contract the rose mosaic virus through root contact with the diseased plant.
At another location on the Davis campus, tour participants heard about the latest developments in greenhouse cut rose integrated pest management.
The three major pest problems with cut roses are powdery mildew, two-spotted spider mites, and western flower thrips. Recently University of California researchers have discovered a tribe of ladybug beetles that feed on the fungus that causes powdery mildew on cut roses. Work has begun in an attempt to learn if releasing this type of ladybug can be used as an effective part of a mildew control program in commercial flower greenhouses.
The predatory mite persimillis already provides effective biological control of spider mites. And this beneficial insect is widely available to greenhouse growers near the California coast because many coastal-area strawberry growers use it in their integrated pest management programs.
But there are no known effective biological controls for western flower thrips. To control thrips, while maintaining biological control of mites, researchers developed a unique system of spraying insecticides only on the areas of the roses where thrips are likely to congregate. “By spraying just around the bud we can reduce the water by 75% and lower the impact on the biological control in the lower part of the plant,” says Michael Parella, the University of California at Davis professor of entomology.
A decade ago the California Pajarosa Floral cut rose nursery outside of Watsonville, California began working on biological control of spider mites, which are high on the list of cut rose pests. Their approach requires unusually vigilant scouting to discover the spider mites when they are still at low enough levels for the predatory mite persimillis to keep them under control.
To maintain this biological control for spider mites, the insecticides that are used to control thrips are sprayed at the lowest possible levels and are directed high on the plant. Blue tape is also stretched prominently throughout the greenhouses to attract and trap western flower thrips.
The jury is still our, however, on the effectiveness of this particular control tool. “My feeling is that when you have millions of thrips coming into the greenhouse, and you have a few thousand go to the blue tape, it mainly makes you feel good,” said Steve Tjosvold, University of California Cooperative Extension farm advisor in Watsonville, California. California Pajarosa also has a head start in satisfying water-quality regulators because the water from the 17 acres of hydroponic roses at the facility is already recycled.
Irrigation sets are calculated to leach 20% of the water out of the bottom, to prevent excess salts from building up in the medium. After water leaches from the bottom of the pots, it is captured and sent to a retention pond on the nursery grounds. From the retention pond, the water is sand filtered and then mixed with fresh well water to irrigate the roses.
In 1993 he converted to hydroponics and began growing his roses in Rockwool on rolling benches. Today there is no Rockwool in the California Pajarosa greenhouses, as the firm has continued to evolve its methods and now grows in a mix of 50% coconut and 50% perlite.
Coconut has proven to be better for cut rose production than Rockwool, and costs about the same. Production increases 20 to 30% by bending the weaker limbs downward. And the firm also increases its productivity by investing in a relatively quick turnover of the plants, as the roses are replaced in just five to seven years.
Between 140 and 150 varieties of roses are grown at California Pajarosa. This extensive variety count includes around 50 varieties of spray roses, another 50 or more varieties of hybrid tea roses and the remainder in miniature roses. “We are not growing as many cut flowers as before, but we are growing more nursery plants, colorful bedding plants,” says Tjosvold. Not long ago growers in Monterey and Santa Cruz counties grew $75 million in cut roses annually.
That figure has dropped to just $20 million, as lower-cost South American imports have taken the market, and production cut flowers of all types are down to $75 million. But as the cut flower trade has declined, local growers have taken advantage of the temperate coastal climate to build a $300 million nursery industry.
“The industry left here, so all the cut flower varieties are coming out of Europe,” said George Marciel, sales director at Rose Gene Technology. “We go to the Netherlands every year and bring back the varieties we like.” Every year Marciel brings back 12 to 15 new cut rose varieties that look like they would fit in the North American market.
These varieties are then grown on natal briar rootstock in the Rose Gene greenhouses to learn how they fare under California coastal conditions. There has not been a dominant red rose variety in the United States market since Kardinal reigned supreme more than a decade ago. The red rose market today is fragmented among six and eight popular varieties, according to Marciel.
And tastes in cut roses are different in the United States, where cut flowers are usually occasion gifts; by contrast, cut flowers are frequently purchased to decorate homes in Europe. “In the United State, it is about how it looks, not how long it lasts, because it is still mostly gift-giving,” Marciel says.
The Rose Gene Technology complex outside of Watsonville used to be a rose research facility. But circumstances have forced the company to diversify and today the complex is divided among a cut flower business, s starter plant nursery for cut rose growers and a potted plant breeding facility for garden roses. And Marciel believes the march of low-wage production could eventually impact the Netherlands.
There are between 61 and 81 ha of cut rose greenhouses in the United States and Canada, which is down from a peak of 202 and 304 ha. The Netherlands, by way of comparison, has 809 to 911 ha of cut rose greenhouses. “Africa is starting to encroach on what they are doing in the Netherlands,” Marciel says. “You can see the long-term trend. I feel kind of like a blacksmith at the turn of the last century.”
