‘Roi de Siam’ is an Old Climbing Tea rose which produces large, semi-double rich pink flowers. In general, roses are a large group of flowering shrubs, most with showy flowers that are single-petalled to fully double petalled. Leaves are typically medium to dark green, glossy, and ovate, with finely toothed edges. Vary in size from 1/2 inch to 6 inches, five petals to more than 30, and in nearly every color. Often the flowers are very fragrant. Most varieties grow on long canes that sometimes climb. Unfortunately, this favorite plant is quite susceptible to a variety of diseases and pests, many of which can be controlled with good cultural practices.
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CharacteristicsCultivar: Roi De Siam
Size: Height: 0 ft. to 0 ft.
Width: 0 ft. to 0 ft.
Plant Category: climbers, shrubs,
Plant Characteristics: high maintenance,
Foliage Characteristics: deciduous,
Flower Characteristics: double, erect, showy,
Flower Color: pinks,
Bloomtime Range: Mid Spring to Mid Fall
USDA Hardiness Zone: 7 to 9
AHS Heat Zone: Not defined for this plant
Light Range: Sun to Full Sun
pH Range: 5.5 to 7.5
Soil Range: Sandy Loam to Some Clay
Water Range: Normal to Moist
FertilizingHow-to : Fertilization for Established Plants
Established plants can benefit from fertilization. Take a visual inventory of your landscape. Trees need to be fertilized every few years. Shrubs and other plants in the landscape can be fertilized yearly. A soil test can determine existing nutrient levels in the soil. If one or more nutrients is low, a specific instead of an all-purpose fertilizer may be required. Fertilizers that are high in N, nitrogen, will promote green leafy growth. Excess nitrogen in the soil can cause excessive vegetative growth on plants at the expense of flower bud development. It is best to avoid fertilizing late in the growing season. Applications made at that time can force lush, vegetative growth that will not have a chance to harden off before the onset of cold weather.
LightConditions : Full Sun
Full Sun is defined as exposure to more than 6 hours of continuous, direct sun per day.
WateringConditions : Moist and Well Drained
Moist and well drained means exactly what it sounds like. Soil is moist without being soggy because the texture of the soil allows excess moisture to drain away. Most plants like about 1 inch of water per week. Amending your soil with compost will help improve texture and water holding or draining capacity. A 3 inch layer of mulch will help to maintain soil moisture and studies have shown that mulched plants grow faster than non-mulched plants.
PlantingHow-to : Planting Roses
Plant roses where they will receive full sun (at least 6 hours) and ample moisture and nutrients. Allow adequate spacing (3 to 6 feet apart depending on the climate) as good air circulation will inhibit foliar diseases. Before planting, soak bare root plants in water for several hours to ensure they are well hydrated. Select a soil site that is well drained. For clay soils amend the soil with organic matter or prepare raised beds. Dig a planting hole big enough to spread out the roots completely, once the center of plant has been set atop a mound. Fill hole with water before planting. Remove broken canes or roots and plant the bush so that the graft union (swollen knob from which the canes grow) is just above the soil level. Fill hole with amended soil and water well. Mound rich soil over the graft union to protect it from the sun. Remove this once leaves have appeared. Container grown roses can be planted almost anytime of year and would be done just as if planting a shrub.
ProblemsPest : Thrips
Thrips are small, winged insects that attack many types of plants and thrive in hot, dry conditions (like heated houses). They can multiply quickly as a female can lay up to 300 eggs in a life span of 45 days without mating. Most of the damage to plants is caused by the young larvae which feed on tender leaf and flower tissue. This leads to distorted growth, injured flower petals and premature flower drop. Thrips also can transmit many harmful plant viruses.
Prevention and Control: keep weeds down and use screening on windows to keep them out. Remove or discard infested plants, keep them away from non-infested plants. Trap with yellow sticky cards or take advantage of natural enemies such as predatory mites. Sometimes a good steady shower of water will wash them off the plant. Consult your local garden center professional or county Cooperative extension office for legal chemical recommendations.
Pest : Spider Mites
Spider mites are small, 8 legged, spider-like creatures which thrive in hot, dry conditions (like heated houses). Spider mites feed with piercing mouth parts, which cause plants to appear yellow and stippled. Leaf drop and plant death can occur with heavy infestations. Spider mites can multiply quickly, as a female can lay up to 200 eggs in a life span of 30 days. They also produce a web which can cover infested leaves and flowers.
Prevention and Control: Keep weeds down and remove infested plants. Dry air seems to worsen the problem, so make sure plants are regularly watered, especially those preferring high humidity such as tropicals, citrus, or tomatoes. Always check new plants prior to bringing them home from the garden center or nursery. Take advantage of natural enemies such as ladybug larvae. If a miticide is recommended by your local garden center professional or county Cooperative Extension office, read and follow all label directions. Concentrate your efforts on the undersides of the leaves as that is where spider mites generally live.
Pest : Whiteflies
Whiteflies are small, winged insects that look like tiny moths, which attack many types of plants. The flying adult stage prefers the underside of leaves to feed and breed. Whiteflies can multiply quickly as a female can lay up to 500 eggs in a life span of 2 months. If a plant is infested with whiteflies, you will see a cloud of fleeing insects when the plant is disturbed. Whiteflies can weaken a plant, eventually leading to plant death if they are not checked. They can transmit many harmful plant viruses. They also produce a sweet substance called honeydew (coveted by ants) which can lead to an unattractive black surface fungal growth called sooty mold.
Possible controls: keep weeds down; use screening in windows to keep them out; remove infested plants away from non-infested plants; use a reflective mulch (aluminum foil) under plants (this repels whiteflies); trap with yellow sticky cards, apply labeled pesticides; encourage natural enemies such as parasitic wasps in the garden; and sometimes a good steady shower of water will wash them off the plant.
Pest : Aphids
Aphids are small, soft-bodied, slow-moving insects that suck fluids from plants. Aphids come in many colors, ranging from green to brown to black, and they may have wings. They attack a wide range of plant species causing stunting, deformed leaves and buds. They can transmit harmful plant viruses with their piercing/sucking mouthparts. Aphids, generally, are merely a nuisance, since it takes many of them to cause serious plant damage. However aphids do produce a sweet substance called honeydew (coveted by ants) which can lead to an unattractive black surface growth called sooty mold.
Aphids can increase quickly in numbers and each female can produce up to 250 live nymphs in the course of a month without mating. Aphids often appear when the environment changes - spring & fall. They're often massed at the tips of branches feeding on succulent tissue. Aphids are attracted to the color yellow and will often hitchhike on yellow clothing.
Prevention and Control: Keep weeds to an absolute minimum, especially around desirable plants. On edibles, wash off infected area of plant. Lady bugs and lacewings will feed on aphids in the garden. There are various products - organic and inorganic - that can be used to control aphids. Seek the recommendation of a professional and follow all label procedures to a tee.
Fungi : Powdery Mildew
Powdery Mildew is usually found on plants that do not have enough air circulation or adequate light. Problems are worse where nights are cool and days are warm and humid. The powdery white or gray fungus is usually found on the upper surface of leaves or fruit. Leaves will often turn yellow or brown, curl up, and drop off. New foliage emerges crinkled and distorted. Fruit will be dwarfed and often drops early.
Prevention and Control: Plant resistant varieties and space plants properly so they receive adequate light and air circulation. Always water from below, keeping water off the foliage. This is paramount for roses. Go easy on the nitrogen fertilizer. Apply fungicides according to label directions before problem becomes severe and follow directions exactly, not missing any required treatments. Sanitation is a must - clean up and remove all leaves, flowers, or debris in the fall and destroy.
Pest : Caterpillars
Caterpillars are the immature form of moths and butterflies. They are voracious feeders attacking a wide variety of plants. They can be highly destructive and are characterized as leaf feeders, stem borers, leaf rollers, cutworms and tent-formers.
Prevention and Control: keep weeds down, scout individual plants and remove caterpillars, apply labeled insecticides such as soaps and oils, take advantage of natural enemies such as parasitic wasps in the garden and use Bacillus thuringiensis (biological warfare) for some caterpillar species.
Fungi : Black Spot
A known rose disease, Black Spot appears on young leaves as irregular black circles, often having a yellow halo. Circles or spore colonies may grow to 1/2 inch in diameter. Leaves will turn yellow and drop off, only to produce more leaves that will follow the same pattern. Roses may not make it through the winter if black spot is severe. The fungus will also affect the size and quality of flowers.
Prevention and Control:Plant resistant varieties for your area. Always water from the ground, never overhead. Practice good sanitation - clean up and destroy debris, especially around plants that have had a problem. When pruning roses, even deadheading, dip pruners in a bleach / water solution after each cut. If a plant seems to have chronic black spot, remove it. A 2-3 inch thick layer of mulch at the base of plant reduces splashing. Do not wait until black spot is a huge problem to control! Start early. Spray with a fungicide labeled for black spot on roses.
Diseases : Blight
Blights are cause by fungi or bacteria that kill plant tissue. Symptoms often show up as the rapid spotting or wilting of foliage. There are many different blights, specific to various plants, each requiring a varied method of control.
MiscellaneousHow-to : Winter Protection for Roses
F. Start off by keeping your plants healthy and vigorous going into the winter - continue to water them properly until the ground freezes. Stop feeding at least 6 weeks before the first frost date as this is the time to start hardening off the plants for the winter. In really cold climates, after a couple of hard freezes, mound soil or heavy mulch 1 foot over the base of plant to protect the graft union. Cut back long canes to 4 foot lengths and bind them together to prevent injury in the winter. Remove soil mounds after all danger of hard frost has passed in the spring.
In milder climates, this process is not necessary, but a good layer of mulch and continued watering up to frost and periodically through winter is a good idea. The best time to prune no matter where you live is at the end of the dormant season, when buds are beginning to swell.
Glossary : Viruses
Viruses, which are smaller than bacteria, are not living and do not replicate on their own. They must rely on the cellular mechanisms of their hosts to replicate. Because this greatly disrupts the cell's functionality, outward signs of a viral infection result in a plant disease with symptoms such as abnormal or stunted growth, damaged fruit, discolorations or spots.
Prevention and Control: Keep virus carriers such as aphids, leafhoppers, and thrips under control. These plant feeding insects spread viruses. Viruses can also be introduced by infected pollen or through plant openings (as when pruning). Begin by keeping the pathogen out of your garden. New plants should be checked, as well as tools and existing plants. Use only certified seed that is deemed disease-free. Plant only resistant varieties and create a discouraging environment by rotating crops, not planting closely related plants in the same area every year.