A Detailed Guide to Orchid Cultivation Methods and Fresh-Keeping, Storage and Transport Techniques

The medium for growing orchids very easily turns acidic. How can this be overcome?

　　

When sphagnum moss is used to grow orchids, after a few days the sphagnum moss becomes contaminated by organic-acid-producing bacteria and turns acidic, and then the orchid root zone easily develops black tips (Fusarium infection).

　　

When orchid-growing media are boiled in water or sterilized at high temperature in an autoclave, why can the problem of orchid black tips not be completely overcome?

　　

Some orchid nurseries boil sphagnum moss or sterilize it at high temperature before using it to grow orchids. Although this can temporarily kill bacteria and insect eggs, after planting the sphagnum moss still turns acidic, causing the orchid root zone to easily develop black tips. This is because after the orchids are planted they are still contaminated by organic-acid-producing bacteria.

　　

How can the black tip problem be reduced when growing orchids?

　　

Black tips in the orchid root zone occur mainly because the medium, such as sphagnum moss, is contaminated by organic-acid-producing bacteria, causing the medium to turn acidic and causing Fusarium to multiply in large numbers (Fusarium grows best at around pH 4). Therefore, raising the pH of the medium can reduce Fusarium infection.

　　

How can the black tip problem be effectively reduced?

　　

Applying small-molecule water-soluble chitosan and actinomycetes diluted 2000 times with water to irrigate orchids can effectively reduce the black tip problem in orchids. Media such as sphagnum moss should be soaked for 1-5 minutes in small-molecule water-soluble chitosan and actinomycetes diluted 1000 times, then drained before planting.

　　

What is small-molecule water-soluble chitosan? What benefits does it have for orchids?

　　

Chitin is extremely widely distributed in nature. For example, the shells of crustaceans (shrimp, crabs, etc.), the shells of insects (cockroaches, butterflies), and the shells (clams, oysters) and internal skeletons (squid) of mollusks all contain chitin. After acid and alkali treatment to remove calcium and protein, chitin is obtained. After chitin is treated with high temperature and strong alkali for deacetylation, chitosan is obtained. Chitin and chitosan are collectively called chitosan.

　　

Advantages of using chitosan on orchids:

　　

1. It allows the medium to be continuously cropped - chitosan can increase beneficial microorganisms in the medium, such as actinomycetes, reduce harmful bacteria such as Fusarium, and eliminate root-knot nematodes, reducing the troubles of continuous cropping obstacles in the medium.

　　

2. It promotes the healing and development of root wounds, increases root hairs, and increases nutrient absorption capacity. It promotes plant growth.

　　

3. It induces the production of phytoalexin in plants, improves crop disease resistance and antibacterial ability, thereby reducing the amount of pesticides used.

　　

4. It increases the calcium content of orchids, which can increase stiffness.

　　

5. It enhances the absorption of trace elements, thereby increasing the reducing sugar content of leaves, advancing harvest, improving quality, and extending the fresh-keeping period.

　　

Actinomycetes are Gram-positive bacteria that are extremely common in soil in nature. More than four hundred species are known. Because most have the ability to produce antibiotics, their application in crop disease control has continued for more than half a century since the earliest report by Waksman in 1943. Similar successful development cases have mostly focused on the production of antibiotic preparations. The best known is the application of streptomycin to the control of bacterial diseases in many fruits, vegetables and flowers. In addition, actinomycetes can also decompose organic matter and produce extracellular enzymes to break down proteins, cellulose, lignin, and chitin, so this property can be used against microorganisms with chitin cell walls. For example, adding chitin to soil can control Fusarium, mainly because the chitinase secreted by actinomycetes can cause the dissolution of pathogenic hyphae.

　　

What are the benefits for orchids of using small-molecule water-soluble chitosan and actinomycetes at the same time?

　　

When chitosan and actinomycetes are used at the same time to irrigate orchids, chitosan has an antibacterial effect and can promote the growth of actinomycetes, inhibit the growth of Fusarium, and promote wound healing. For example, it is very effective against anthracnose, which causes black leaf spots.

　　

What effect does ethylene have on orchids?

　　

Orchids are quite sensitive to ethylene. Just 0.01 ppm of ethylene can cause Vanda flowers to wilt. Next are those of Southeast Asia. Dendrobium, Phalaenopsis, and Paphiopedilum follow. Oncidium is not sensitive to ethylene. Phalaenopsis produced in the province, when treated with 0.09 ppm ethylene, can be induced to age, producing aging symptoms such as flower drop and dehydration-induced wilting. Ethylene causes orchid sepals to wither at the tips and the lip to turn red. The early symptoms of aging are transparent sepals and petals, followed by prominent veins and the formation of an abscission layer, leading to floret drop.

　　

In addition, as flowers mature or after dehydration, high temperature, or disease, their sensitivity to ethylene increases.

　　

Why do potted orchid seedlings in bud turn yellow in the leaves and drop their buds during storage and transport?

　　

Yellowing leaves and bud drop in potted seedlings in bud during long-distance transport are mainly caused by the effects of excessively high ethylene concentration and bacterial infection.