We have had thunderstorms and rain this month. Hopefully the summer heat will soon be a thing of the past as the rainy season starts.
Prosperous: Phosphorus is necessary for strong root growth and flowering of plants.
Gardeners, now is the time to get busy. Take out the pruning shears and trim your trees and shrubs. After you are done, bring out the shovel and cultivate the soil, then feed the plants.
There are two schools of thought about the proper time to prune trees. One advocates trimming after the rainy season, when the plants stop growing and become dormant. The other is for trimming the plants at the start of the rainy season, when plant growth resumes. I happen to subscribe to the latter, as plants recover from their wounds faster when they are growing.
An excellent pruning job is hardly noticeable. Thin, weak or dead branches are removed yet the tree looks untouched. There is no profusion of new growths as the initial branch has been cut back to the trunk or main supporting limb, thus leaving no stub.
Potty for potassium: Plants need potassium for more and better fruit.
On the contrary, there is nothing more noticeable than a poorly pruned tree. Leaving a stub when cutting off a branch does not only make the tree look ugly, but from every stub four to six new branches grow. Allowing these new branches to develop will necessitate more pruning in a year or two.
Once you have snipped off the dead branches and trimmed your tree, it is time to cultivate the soil. Cultivating aerates the soil and encourages the growth of bigger and healthier roots. However, don’t dig too deep in order not to disturb or hurt the tree’s root system. A wounded root is open up to a disease setting in, which could be fatal for the tree.
The start of the rainy season is also the perfect time for fertilising plants. Whether they are planted in the ground or in pots, plants are able to absorb and utilise fertilisers better during the growing period, that is, during the rainy season. After cultivating you can either topdress the soil with compost or well-decomposed animal manure, or dig in a chemical fertiliser around the perimeter of your plants’ outer leaves, where the tips of the feeder roots are located.
Manure and compost are organic fertilisers but, although they contain trace elements and small amounts of the major nutrients, their main function is to improve soil texture for better drainage. Organic matter also provides a healthy environment for the growth of soil bacteria and fungi, which are needed to break down chemical, or inorganic, fertilisers into soluble compounds that plants can absorb.
When buying plants, vendors’ advice on how much and how often the plants must be fertilised vary. For ornamental plants some say once a week, others every 15 days, while some say every month or every six weeks. Ordinary fertilisers dissolve quickly; after a month, very little remains. Where watering is frequent, regular fertilisers quickly leach out of the pot. Some plants, therefore, will benefit from feeding every six weeks.
Sticking out: There is nothing more noticeable than a poorly pruned tree.
How much to apply? Read the label for dosage. Usually it depends on the size of the plant. For small potted plants, use a teaspoon, and add more as they become bigger. For light feeding, apply a little but more frequent, with the fertiliser dissolved in water. A spoonful or two for every 20 litres of water, applied every 10 to 15 days should make your plants happy.
Most fertiliser applications are for the major elements, or macronutrients, namely, nitrogen, phosphorus and potassium. Nitrogen promotes vegetative growth; if the soil lacks nitrogen, plants become stunted and the leaves turn yellow. Phosphorus is necessary for strong root growth and flowering of plants; without it flowers are few or they may prematurely wither and fall. Potassium aids in cell division and in the manufacture of food; when it is deficient in the soil, the root system and stems become weak, and yield is subsequently reduced.
Some fertilisers are formulated to contain only one element, or the three elements are present in different amounts. NPK 46-0-0 (urea), for example, contains only nitrogen, which is needed most by all plants in the early stages of growth and development. It is also applied to leafy vegetables, and foliage plants like ferns and philodendrons, as these do not need fertilisers that promote growth of flowers or fruit.
Fertilisers which contain more phosphorus than nitrogen and potassium are formulated for flowering plants. For fruit trees, apply a fertiliser high in phosphorus and potassium, which aid flowering and fruiting more than vegetative growth.
Plants also utilise essential elements in very small amounts. Called trace elements, or micronutrients, these include boron, iron, molybdenum, manganese, zinc, copper and chlorine. Boron affects flowering and fruiting and other processes in the plant; when it is lacking, terminal buds die, and young leaves thicken, become leathery and turn yellow. Iron helps in the formation of chlorophyll, the green colouring essential for the plant’s manufacture of food. Iron deficiency shows up as yellowing of veins, known as interveinal chlorosis, in young leaves and in severe cases, leaves may become whitish. Manganese is crucial to photosynthesis, the process in which plants convert energy from the sun into food; when it is lacking in the soil, interveinal chlorosis shows up in young leaves, as in iron deficiency.
Micronutrients can be safely administered by foliar application, or spraying the leaves with fertiliser diluted with water. Again, the dose is on the label.
When fertilising plants, more does not mean better. If your plants are healthy and growing well, it means they are getting all the nutrients they need and do not need fertilising just yet. Excessive fertilisation is not only economically wasteful, but it allows the build-up of acidity in the soil which could adversely affect and even kill your plants. What’s more, it encourages leaves to be succulent, which insect pests find attractive.
Leafy love: Green vegetables and foliage plants benefit from fertilisers high in nitrogen.
This source first appeared on Bangkok Post Lifestyle.