Rough Guide:

Plants need four things to grow: Water, Light, Carbon and Nutrients.

Light for photosynthesis. It supplies the energy required to generate the chemical reactions involved.

CO2 for photosynthesis.

The plants require nutrients to grow, to improve strength, to flower and for defensive purposes. A well balanced “died” will produce strong healthy plants, less susceptible to pests, bacteria and fungi attacks. Deficiency in one or more nutrient or trace elements, can make a plant look sick. Nitrogen, Phosphorus, Potassium and Magnesium deficiencies can result in yellowing of the leaves (chlorosis) and eventual death of the leaves (necrosis).

Nobody ever studied the trace element requirements of orchids and how these assist the orchids in their growth. In nature, plants take everything they need from the ground and/or the air. Nutrients are mobile and can be translocated from older to new leaves. The translocation depletes older leaves of these essential nutrients and that leads to chlorosis and necrosis.

We divide Nutrients into two main groups:

The Macronutrients: Nitrogen, Phosphorus, Potassium, Calcium, Magnesium and Sulphur.

The Micronutrients: Iron, Manganese, Boron, Zinc, Copper, Molybdenum and Chlorine.

I divide the Macronutrients further into two groups: Nitrogen (N) and Phosphorus (P) + Potassium (K).

Nitrogen(N) is needed to stimulate leaf and stem growth. As Nitrogen migrates from the old to the new growth older leaves turn yellow and may fall. Deficiency results in poor plant growth and yellowing of the lower leaves (chlorosis). Excess results in very fast but weak growth.

The nutrient Phosphorus and Potassium work best together because the two complement each other in many ways.

Phosphorus(P) is important for the development of a healthy root system, and is very useful during blooming and seed setting. Deficiency causes plants to grow slower, leaves to drop early, and stems and leaves to look unhealthy and turn purplish. Lack of flowers can also be traced back to Phosphorus deficiency.

Potassium(K) is predominantly required to stimulate flowering and to increase disease resistance. Deficient plants can show marginal necrosis in the leaves, and in severe cases necrosis in the inter-veinal spaces. Excessive use of Potassium can cause Calcium and Magnesium deficiencies.

Calcium(Ca) is a major component in cell walls and important for root growth. A good root system is important for calcium uptake. Deficiency may result in slow growth and dieback of shoots.

Magnesium(Mg) is vital to chlorophyll production and plays part in most enzyme reactions.

Sulphur(S) is present in proteins and needed for chlorophyll formation.

The Micronutrients are vital to plant growth like vitamins to humans.

Copper(Cu) is acts as a catalyst for several enzymes and is required for root formation. Copper deficiency reduces growth and stunts root development. Deficiency can kill the plant.

Iron(Fe) is a key catalyst in the chlorophyll production. Deficiency can stunt vigour. The presence of lime can cause Iron deficiency.

Manganese(Mn) works with plant enzymes to reduce nitrates before producing proteins. It requires the right pH of the soil. Deficiency can stunt the vigour of the plant.

Boron(B) is needed for cell division, protein formation, pollination, and seed production. Adding Borax to the soil will correct the deficiency; however, be aware that Borax is an herbicide. Excessive use of magnesium sulphate will cause a boron imbalance. Deficiency causes poor development of new growth.

Molybdenum(Mo) is essential to nitrate enzymes. It assists in fixing nitrogen and helps in protein formation. Deficiency causes the leaves to turn pale with scorched looking edges, and is responsible for irregular leave growth. Excess is equally as harmful.

Zinc(Zn) if required for the production of proteins and affects plant size and growth. Deficiency causes yellowing and curling of small leaves.

Micronutrients are relative common. Some are found in drinking water (Fe, Cl, B, etc), other are present in pesticides (Cu, S, etc). The use of Dolomite adds Ca, Mg, Mn, Fe, etc into the soil.

How to use Macronutrients to your advantage:

Under normal circumstances the plants require equal amounts of Nitrogen and Potassium and half to one third less Phosphorus. Lets say: N:P:K: = 5:3:5

By changing the ratio 5:3:5 you change the plants behavior.

If you decrease the amount of Potassium and at the same time you increase the amount of Nitrogen, lets say 8:3:3, you practically force the plant to grow. The higher the amount of Nitrogen in relation to the other two the faster the plants will grow. That can be very dangerous because the stems of fast growing plants are also very weak and many times can not stand straight.

If you go the other way, decrease Nitrogen and increase both Phosphorus and Potassium, lets say 3:6:6 before the buds appear, will encourage the plant to flower; however, a stronger combination, lets say 0:10:10 before budding, you FORCE the plant to stop growing, and to flower. If you try to force the plants to flower, make sure that you go back to normal (5:3:5) as soon as the flower buds appear.