Hydrangea macrophylla Shamrock - Shamrock hydrangea has lacecap-type inflorescences with double-type sterile flowers of pink colored becoming dark red
Hydrangea macrophylla Shamrock also called as Shamrock hydrangea, is a cultivar in the genus Hydrangea. This cultivar was discovered by Corinne Mallet in a controlled environment in Varengeville Sur Mer, France.
DESCRIPTION OF HYDRANGEA MACROPHYLLA SHAMROCK - SHAMROCK HYDRANGEA
Hydrangea macrophylla Shamrock is a cross between 2 unknow selection of Hydrangea macrophylla. Asexual reproduction of the plant by softwood cuttings taken in Varengeville Sur Mer, France since the spring of 2000, has shown that the unique features of this plant are stable and reproduced true to type in successive generations.
It is a bushy perennial shrub which reaching 60 cm tall by 50 cm spread in 4 years with vigorous growth, upright and outwardly spreading plant habit. When pinched, the plant is freely branching, about 24 lateral branches per plant. The leaves are opposite, about 20 cm long by 8.5 cm wide, ovate, acute apex, attenuate base, crenate to serrate margin, green colored.
Shamrock hydrangea blooms in mid-summer on the 6 cm long by 19 cm in diameter, flattened terminal clusters in a lacecap formation with about 7 double-type sterile flowers and 137 fertile flowers per terminal cluster. The flowers are pink-colored becoming closer to dark red. Pink flowers can be changed to blue by acidifying soil and maintaining the pH in the 5.0 to 5.5 range. Adjusting a soil’s pH will need to be done annually in order to achieve and maintain proper results. The results from a soil pH test kit will determine existing pH levels and the need to add lime or sulfur in order to adjust the soil accordingly. Tap water may alter test results; therefore, it is important to use deionized water with a soil testing kit. Sulfur should be added in order to lower a soil’s pH. Lime should be added in order to raise a soil’s pH. Elemental sulfur, also called flowers of sulfur, or iron sulfate are better alternatives to using aluminum sulfate because aluminum can reach toxic levels in the soil. While aluminum is a key element to lower a soil’s acidity and change the color of hydrangea flowers, it can also become toxic at high levels.
HYDRANGEA MACROPHYLLA SHAMROCK - SHAMROCK HYDRANGEA CARE AND CULTURE
Cultural information should only be used as a guide, and should be to be adapted to suit you. Your physical location; where you grow your plants, how much time you have to devote to their care, and many other factors, will need to be taken into account. Only then can you decide on the cultural methods that best suit you and your plants.
Light:
Hydrangea macrophylla Shamrock love the warm morning sun, but they dislike the heat of the afternoon. The best place for the plant is in a sheltered location with sunny mornings and shady afternoons. Avoid planting directly underneath trees, which can lead to competition for water and nutrients. High winds can rip and damage leaves and destroy the flowers. Although they can be successfully grown in full shade, they will not bloom well.
Temperature:
Shamrock hydrangea prefers a cool location, from 18° to 24°C. The plant may suffer from considerable branch dieback during the cold months and will benefit from winter protection. Winter protection can be provided by constructing a wire framework around the plant and filling the space with shredded leaves to a depth of approximately 10-12” for insulation. Cold winters and late spring frosts can often kill flower buds, preventing plants from blooming in the spring. When unexpected cold weather is predicted in late spring or early summer after winter protection has been removed, it may be necessary to cover tender plant with cloth, burlap, or heavy paper to protect flower buds. Plastic should never be used as winter protection because it may damage tender plant tissue.
Substrate, growing media:
Hydrangea macrophylla Shamrock are best planted in well-drained, moist soil, preferably a fertile sandy or silt loam with greater than 1% organic matter. The plant can also grow in clay soils with proper water management. When grown in container, the plant needs a well-drained substrate with sphagnum peat moss to increase substrate water holding capacity, and perlite or pumice to maintain adequate air space.
For pink flowers, try to maintain media pH in the 6.0–6.2 range, especially during the finishing stage of production. Higher pH can be maintained by amending the potting media with sufficient levels of calcitic or dolomitic limestone.
For blue-purple flowers, try to maintain media pH in the 5.0–5.5 range, especially during the finishing stage of production. To maintain the media acidity, drenches of aluminum sulfate solution are applied to the media at regular intervals.
Humidity and Watering:
Shamrock hydrangea prefers consistent moisture but dislike wet feet. The plant should be watered thoroughly at least 3 times a week. Always water the plant all the way around the container, not just in one place. Water should come out the bottom of the pot. Never let it sit in water which will cause the roots to rot away. Mulch to help conserve moisture and cool the root system. A two- to three-inch layer of mulch will help to conserve moisture.
Fertilizer:
Fertilizing is generally not recommended unless a nutrient deficiency is observed. The plants may need little fertilizer in rich soil with organic matter applied yearly. Avoid using too much nitrogen, too much nitrogen can produce excessive green growth at the expense of flowers. If you do fertilize, do a little research to find out exactly what your plant might need, and always apply as directed and read and follow all label directions.
Pruning:
The plant bloom on last year’s woody stems. Late heavy pruning will remove your blooms for the year! Instead, prune out one half to all of the older stems (they have side branches) at ground level in June and July when you are cutting flowers for arrangements or drying. This pruning method will allow more light and air circulation within your plant for disease control, while at the same time reducing size and increasing flower cluster size. Prune in late winter if you missed the opportunity in summer. Remove dead branches or frost-damaged leaves and stems as soon as you notice them. Wait to prune new plants until they are 5-6 years old.
Propagation:
Hydrangea macrophylla Shamrock is mainly propagated by softwood cuttings. The cutting should be taken from non-flowering green woody stems and cut at the base. Each cutting should have at least one leaf node or terminal bud. It is important not to damage the buds while obtaining the cuttings. Dip your cutting into your rooting hormone, then place into the sterile media that should consist of one part peat and one part medium to fine grade perlite, vermiculite, or sand. Spray the plant until wet but dont over water it. Watering is important for the first week, three times a day is recommended for the first week when top soil feels dry. Dont place the plant in direct sunlight or wind. After a few weeks you should see growth from your cuttings.
Pests and diseases:
Shamrock hydrangea are almost trouble-free. However, certain pests and diseases can attack. The most common time for them to do so is in the summer months. They most commonly suffer from powdery mildew, aphids, spider mites, yellow leaves and leaf spots. All of these are common to spot and treat, providing you catch the disease or pest early.
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