Key Techniques for Summer Cuttage of Woody Flowering Plants
In summer, the temperature is high and the humidity is low, the leaves of the cuttings transpire heavily, and the water absorbed at the cut end of the stem base cannot balance the water lost from the upper part, which is the key factor making summer cuttage of woody flowering plants difficult to survive. However, the cambium meristem of summer cuttings is highly active, and under conditions of high temperature and high humidity, especially with the action of rooting media such as ABT rooting powder or naphthaleneacetic acid, the wounded cuttage site heals and roots easily, and the rooting time of the cuttings can be greatly shortened (spring cuttage generally roots in about 40 days, while summer cuttage roots in 10-15 days), and the survival rate is also greatly improved. Especially for some species that are difficult to root in spring cuttage, such as camellia, osmanthus, banana shrub and purple magnolia, it is an effective propagation method.
I. Requirements for the cutting bed
The cutting bed should be located in a ventilated, shaded spot with good drainage and irrigation, away from direct western sun. The cutting bed should be made in the style of a raised bed that is slightly higher in the middle and slightly lower around the edges; the bed surface should have fine soil, firm on top and loose below, and be level. The bed furrows should be deeper than 20 cm to prevent waterlogging from causing rot at the base of the cuttings. For precious woody flowering plants propagated in small numbers, pot cuttage can also be used. The bed soil is the substrate for the survival of the cuttings, and the cutting bed soil must be clean and free from infection by pests and diseases. Therefore, when leveling the cutting bed, use 0.5% potassium permanganate solution or 500-fold dilution of 50% carbendazim or 58% mancozeb to spray the bed surface evenly for disinfection, and remove underground pests such as cutworms. Before cuttage, cover the bed surface with a 3 cm thick layer of uncontaminated fine loess and a 2 cm thick layer of fine river sand, or either one alone. Before cuttage, spray the bed surface several times with 1% to 2% fungicide (such as carbendazim, thiophanate-methyl, chlorothalonil, etc.) to ensure the soil layer is soaked to more than 3 cm; the fungicidal water can be sprayed while cutting.
The type of substrate soil can be selected according to the different species of woody flowering plants being propagated. For example, for camellia, osmanthus, banana shrub, Chinese rose, Oyama magnolia, rhododendron and purple magnolia, yellow subsoil is most ideal; for littleleaf box, golden-edged privet, rose of Sharon, Boston ivy, oleander and Chinese euonymus, sandy loam is better; for gardenia and mahonia, plain sand as the substrate is best for cuttage; for hibiscus, Chinese lantern flower, hydrangea, Chinese snowball and bougainvillea, humus soil is suitable as the substrate.
II. Cuttage methods
Cuttage is divided into root cuttage, leaf cuttage and stem cuttage. Greenwood cuttage refers to the cuttage of current-year semi-lignified new shoots.
Summer cuttage can be carried out from late May to mid-July. For osmanthus, camellia, hibiscus and hydrangea, cuttings of slightly stronger semi-lignified degree root most easily, and summer cuttage should be done earlier. For box (both large and small species), French holly, golden-edged privet, purple magnolia, banana shrub, Chinese rose, rubber tree, gardenia and Chinese euonymus, fully lignified cuttings root easily, and summer cuttage should be done somewhat later. Cuttings should preferably be shoots from the middle and upper part of the crown that are well developed, robust, have buds and are free from pests and diseases.
Excess leaves on the cuttings should be cut off as much as possible to reduce leaf transpiration. For osmanthus, camellia, hibiscus, gardenia and banana shrub, 2 leaves can be retained; for box, golden-edged privet, Chinese euonymus, forsythia, winter jasmine, serissa, oleander and littleleaf gardenia, several leaves can be retained; for rubber tree and purple magnolia, only half a leaf is retained; for Chinese rose, Boston ivy, Oyama magnolia and monstera, no leaves need be retained. When thinning leaves, the cortex must not be torn.
The cutting is inserted into the substrate to a depth of about 1/2 or 2/3 of the cutting length (10-15 cm), and the cuttage density should be such that the leaves do not overlap each other. For camellia, osmanthus, banana shrub and Oyama magnolia, after cuttage water once thoroughly, set up bamboo arches on both sides of the cutting bed (height greater than 40 cm), cover with light-transmitting plastic film to retain warmth, and add a shade shed (shade shed height greater than 60 cm), or cover with a shade net with a light leakage rate of 50% to cover around the cutting bed, which can significantly increase the cuttage survival rate and shorten the rooting time; however, for most woody flowering plants, it is only necessary after cuttage to water thoroughly and build one layer of shade shed for shading, to prevent direct sunlight from hitting the film.
In addition, during cuttage it is also necessary to collect shoots, cut cuttings, treat with medicinal liquid (rooting powder, etc.), insert cuttings, water and shade in immediate succession, so as to reduce water loss from the cuttings themselves. Cutting collection can be combined with pruning of the seedlings; after the cuttings are taken from the mother plant, immediately sprinkle water to keep them moist to prevent water loss and wilting. The length of the cuttings is generally 4 cm to 10 cm, but it must be ensured that the cuttings have no fewer than 2 nodes, and the cuts at both ends of the cuttings should also be smooth, and must not be split or have damaged bark, etc.
III. Management after cuttage
Within one month after cuttage, check 1 to 2 times a day, mainly to control temperature and light, maintain moisture and shade, frequently spray water on the leaves and irrigate the cutting bed, keep the bed surface moist, lower the bed surface temperature, and create good rooting conditions for the cuttings.
If the shed film is found to be torn, repair it promptly with adhesive tape, and adjust the height of the shade net at any time to prevent the shade net from drooping onto the light-transmitting shed film.
After the cuttings have rooted, appropriately reduce watering and apply an appropriate amount of dilute liquid fertilizer to accelerate the rooting and growth of the cuttage seedlings. In autumn, pay attention to drought prevention, and transplanting can be carried out the following spring.