Poinsettia is an important ornamental flower in the garden because of its bright color and long flowering period.
For ground planting, flower beds, flower fences or foundation planting can be arranged; It blooms at Christmas and New Year's Day, so it is a very popular potted flower.
Poinsettia is an evergreen shrub with a plant height of 6-7 meters, smooth stems and milk.
Leaves alternate, elliptic to lanceolate, 10 ~ 20 cm long, obtusely serrate or even split or entire, with soft hairs on the back.
The leaves under the inflorescence at the top of the stem are narrow, bract-like, usually entire, and scarlet when flowering, which is the main part of appreciation.
Terminal cups, arranged in cymes, with light green involucres.
Flowering period is 65438+February to February of the following year.
At present, the main horticultural varieties cultivated are Yipin Bai, Yipin Powder and Double Poinsettia.
Poinsettia prefers cold and warm weather to frost.
When the sunshine is sufficient, the growth is best at 20 ~ 30℃, and it stops when it is lower than 12℃. The optimum temperature for flower bud differentiation is 15 ~ 19℃, and flower bud differentiation cannot be carried out below 15℃.
It grows vigorously under strong light and is a typical short-lived plant.
The requirements for soil are not strict, but the fertile sandy loam with slight acidity (pH 5.5 ~ 6.5) is the best.
Not dry, because its leaves are thin and wide. If the environment is too dry or under the scorching sun, the leaves will scorch and curl.
Not resistant to water and humidity, too much water will lead to root rot.
Poinsettia grows fast, its internodes are long, and its plant shape is often ugly. In order to make plants shorter, with symmetrical branches and beautiful posture, methods such as pinching, pruning and bending, and applying growth inhibitors are often used for dwarfing and shaping, so as to achieve the effect of plump shape and beautiful dwarfing.
Poinsettia is a flower bud differentiation type with terminal buds, and the top of each branch forms a large inflorescence. Therefore, in order to cultivate the multi-flowered plant shape, it is necessary to promote the growth of lateral buds and form multi-branches.
There are four kinds of coring methods: forced coring, middle coring, weak coring and weak coring with young leaves removed.
Strong core removal refers to picking until the leaves are fully unfolded, generally about 6 ~ 7 cm; Moderate coring refers to picking until the upper two leaves are completely unfolded, usually about 3 ~ 4 cm; Weak enucleation only removes the center of terminal bud, which is generally less than 2 cm. Weak core removal and young leaves removal can make more branches and more compact and complete plant types.
With the increase of denucleation intensity, the obtained plant shape will be wider and the branch length will be more tidy.
The number of coring times will affect the number of flower branches, and the number of coring times for cultivating plants with large pot diameter is usually more than 2 times.
The first coring after planting should be carried out when the plant grows 6 leaves, and each plant can grow 3 ~ 6 lateral buds.
Only two leaves are needed for the second coring.
It takes 4 ~ 5 weeks for each coring to resume growth, and the time and times of coring should be determined according to the controlled plant type and the expected flowering time.
The poinsettia that blooms at Christmas should be picked before mid-September at the latest, otherwise the ideal plant type cannot be achieved.
During the plant growth period, it bends in time with the growth of branches.
Every new shoot length 15 ~ 20cm will bend 1 time.
Branches should not be bent strongly, so as not to break and cause "dead bending", usually in the afternoon when branches have less water.
Soften the branches before bending.
Pay attention to the uniform distribution of branches and keep the same height when making bends.
Bend in the same direction.
Put the strong branches around and the weak branches in the middle. Strong branches bend more than weak branches to balance their growth.
Tie it with a plastic rope when bending.
The last bend should be about 20 days before flowering, so that the branches can be about 15 cm long before flowering.
If you bend too early, the branches will grow too long, swing easily, and the plant state is not beautiful; It's too late, the branches are too short and the ornamental value is not high.
The plant shape control of poinsettia can also be treated with growth regulators.
After coring, it is effective to spray dwarfing agents such as CCC and paclobutrazol on the leaves when the lateral buds grow to 3 ~ 4 cm.
Its concentration varies with cultivated varieties, treatment time and treatment temperature, and each variety should be tested for efficacy before use.
When the temperature is higher than 28℃, dwarfing agent should be avoided, and it is best to use it on cloudy days or before sunset in the evening.
It is suggested that poinsettia should not be treated with dwarfing agent 6 weeks before flower bud differentiation, so as not to affect the flowering quality.
After poinsettia blooms, it is pruned after leaving the house in early spring, combined with changing pots.
First, cut off the old roots and withered, sick and weak branches. In order to concentrate nutrition and make new branches grow sturdily, 1 ~ 2 buds are left at the base of each lateral branch for short cutting, and new buds are removed at any time except the remaining buds.
During the growing season, 1 ~ 2 coring can be carried out to promote the growth of lateral branches.