GREEN FINGERS
For some types of plants, pruning can be most helpful
NORMITA THONGTHAM
Don Rigby sent me an email saying that he has a plant called "wassana", which is now very tall. "I need to chop the top off. Please could you tell me how much I can chop off and if it is possible to re-grow the chopped off portion," he writes.
Don did not say exactly how tall his wassana (Dracaena fragrans) is, but yes, the start of the rainy season is the perfect time for pruning. And yes, he can propagate the cuttings if the wood is mature enough.
Wassana is a hardy plant and it won't suffer even if he cuts it in half. New buds will soon grow again, not just one or two but maybe even more.
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| Dracaena and other ornamental plants with woody stems can be propagated by cutting. — PHOTOS: NORMITA THONGTHAM |
When pruning, make sure to cut just above a bud or a good branch. If the cut is between two buds, leaving a stub, no nourishment will pass through the tissue below the cut and the stub above the cut will wither and die. It will then become a breeding ground for disease that can damage if not kill the whole plant.
If the chopped off portion is long, cut it into several pieces about one foot long. Dip the lower part of the cuttings in a rooting hormone, then insert in a pot filled with moist river sand and placed in a shady area. Or leave the cuttings to heal for a day or two before inserting the lower part in the sand. Keep the sand moist but not soggy until new leaves and roots develop, in about three weeks or so.
Once new leaves and roots have developed, move the pot in a place where there is filtered sunlight. Wait another week or two, then transplant the cuttings when the roots are strong enough. You can check this by gently pulling a cutting; if it resists, it means that the roots are well established and the plant is ready for transplanting.
The same method of propagation can be used for other ornamental plants with woody stems, such as schefflera, croton, hibiscus, plumeria or frangipani, rose, butterfly bush, giant Indian milkweed and hydrangea, etc.
Speaking of hydrangea, Pia Hutchinson sent me an email saying that she is having a problem getting her hydrangea to bloom. "Do you have any suggestion?" she asks.
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| Hydrangeas perform better where the climate is cold. |
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First of all, hydrangeas perform better where the climate is cold, such as on the highlands of Chiang Mai, Loei and Phetchabun. The potted plants with beautiful heads of flowers that you see in Bangkok plant markets were probably grown in nurseries in these provinces.
Hydrangeas may bloom in Bangkok, but this depends on many factors. First, the soil. Some nurseries use rice husk with just a small amount of soil as planting material for potted flowering plants. After the flowers have withered, the plants slowly die. Hydrangeas prefer well-drained, loamy soil enriched with compost and/or well-rotted animal manure.
Second, the variety. Some types of hydrangea like to be cut back after flowering, while in others only dead wood needs to be pruned, or pruning is done only every two years or so, or when they get very big. Some varieties have flowers that grow from old stems, so that if you prune the old stem you will also be cutting the flower buds. Others have flowers that grow from new stems.
Third, light. Some of our hydrangeas are planted in a plot where they get full sun, but in the summer when the sun gets too hot, some parts of the flowers tend to get sunburned. We have just planted another 200 plants, this time under a black straw roof called saran, which cuts the sunlight by half. We will see which plants will bloom better: The ones in full sun or those under filtered light.
You can place your hydrangea where it gets sun in the morning and shade in the afternoon, but never put it where it does not get enough sun, such as under a tree. Plants need at least four hours of sun in order to bloom.
Fourth, nutrients. Feed your hydrangea complete fertiliser (NPK 16-16-16) for general health, but to induce flowering, you will have to change the fertiliser to one with high levels of potassium, that is, the last number must be higher than the other two. Remember that feeding your plants a small amount every month is better than overfeeding them every few months.
Last but not least, water. Drench the soil to make sure that all the roots get moisture, then wait another day or two before watering again. Too much water is as destructive to the plant as too little water.
Post your questions on the http://www.thaigreenfingers.com/ forum, or send email to normita@ thaigreenfingers.com.
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