Soil
Soil, water and sun are the three most important things in gardening. Where I live, water is taken care of naturally and gardeners never have to worry about it. If plants do not like a lot of water, they will not thrive and there is nothing one can do about it, except keeping them undercover. Sun is another matter as there is not much to go around, not even in south facing gardens (not even if the sky is blue!). But most plants still do well with what is available. Although my garden is north facing, so I am always on the look out for plants who do not mind a bit of shade.
Soil can be more tricky. To begin with, there are different types of soil, according to the RHS:
Another important aspect of soil type is pH. Some plants thrive in acid soils, others in alkaline soils, and a lot are not picky about it as long as the soil does not fall into the extremes of the pH scale. However if the soil is very acid (below 5), it will be necessary to add lime to it to reduce acidity. If the soil is acid (between 5 and 6), it is perfect for ericaceous (lime-hating) plants such as rhododendrons, camellias and heathers, and lime will only need to be added to grow other plants. Moderately acid soils (between 6 and 7) are good for most plants and do not need to be treated for acidity. Alkaline soils are a problem as they are always poor in nutrients. Sulphur, iron sulphate and other acidifying agents can sometimes be added to reduce pH. Clay soils often require very large amounts of acidifying material, but soils with free chalk or lime are not usually treatable.
Organic matter can have many origins, but garden compost and farm manure are the most common. Unfortunately the term compost is commonly used to mean both garden compost and material used to fill containers. However, on the one hand, both compost and manure are too rich and too poorly drained to make good potting or growing media. On the other hand potting composts also are an expensive and not especially effective way of improving soil. In conclusion, they are two very different things with very different uses, that can be easily confused, not only because they share the same name, but also because they kind of look the same. Organic matter should be added in order to improve the soil. It can be either mixed in the soil to improve the texture and quality of poor soils, or simply used on top of it, like a mulch (the rain will wash the nutrients down to the soil). Late winter or early spring (February and March) is the ideal time to mulch (not only to enrich the soil, but in addition weeds will be prevented from germinating as the soil warms in spring).
Fertilizers: lots can be said about them. The most important thing to understand is their chemical composition. This is mainly based on the three major plant nutrients:
There are other important nutrients your plants need, for example (source):
Inorganic fertilizers are produced by the chemical industry, they are very "pure" in the sense that they will probably not contain the extra nutrients listed above and also they are more concentrated and act more quickly. They are also more aggressive (see below). Organic fertilizers are probably better for your garden. They are slower too act (slow release), because their molecules have to be broken down by soil organisms before the nutrients within them are released for plant use. Examples of organic fertilisers include: seaweed, hoof & horn, dried blood, fish blood & bone, bone meal, poultry manure pellets and liquid comfrey or nettle feeds. These can be used either as top dressing, base dressing (before sowing or planting) or mixed in the soil.
A word of caution: too much fertilizer can damage plants and even kill good bugs like earthworms. This is specially true of inorganic fertilizers. Note that fertilizers do not improve the soil, but, when used correctly, they boost plant growth, improving health and providing more flowers or better crops.
Soil can be more tricky. To begin with, there are different types of soil, according to the RHS:
- Clay soils
- are heavy, high in nutrients, wet and cold in winter and baked dry in summer
- Sandy soils
- are light, dry, warm, low in nutrients and often acidic
- Silt soils
- are fertile, light but moisture-retentive, and easily compacted
- Loams
- are mixtures of clay, sand and silt that avoid the extremes of each type
- Peat
- soils are very high in organic matter and moisture
- Chalky soils
- are very alkaline and may be light or heavy
Another important aspect of soil type is pH. Some plants thrive in acid soils, others in alkaline soils, and a lot are not picky about it as long as the soil does not fall into the extremes of the pH scale. However if the soil is very acid (below 5), it will be necessary to add lime to it to reduce acidity. If the soil is acid (between 5 and 6), it is perfect for ericaceous (lime-hating) plants such as rhododendrons, camellias and heathers, and lime will only need to be added to grow other plants. Moderately acid soils (between 6 and 7) are good for most plants and do not need to be treated for acidity. Alkaline soils are a problem as they are always poor in nutrients. Sulphur, iron sulphate and other acidifying agents can sometimes be added to reduce pH. Clay soils often require very large amounts of acidifying material, but soils with free chalk or lime are not usually treatable.
Soil improvement and fertilizers
As mentioned above, even the best soil needs regular treatment. Plants growing in a garden will feed of organic matter and nutrients available in the soil and these will need to be replaced. There are 2 main ways this is done: adding new compost or manure which are rich in organic matter regularly, feeding with fertilizers.Organic matter can have many origins, but garden compost and farm manure are the most common. Unfortunately the term compost is commonly used to mean both garden compost and material used to fill containers. However, on the one hand, both compost and manure are too rich and too poorly drained to make good potting or growing media. On the other hand potting composts also are an expensive and not especially effective way of improving soil. In conclusion, they are two very different things with very different uses, that can be easily confused, not only because they share the same name, but also because they kind of look the same. Organic matter should be added in order to improve the soil. It can be either mixed in the soil to improve the texture and quality of poor soils, or simply used on top of it, like a mulch (the rain will wash the nutrients down to the soil). Late winter or early spring (February and March) is the ideal time to mulch (not only to enrich the soil, but in addition weeds will be prevented from germinating as the soil warms in spring).
Fertilizers: lots can be said about them. The most important thing to understand is their chemical composition. This is mainly based on the three major plant nutrients:
- Nitrogen (N)
- For green leafy growth
- Phosphorus (P)
- For healthy root and shoot growth
- Potassium (K)
- For flowering, fruiting and general hardiness
There are other important nutrients your plants need, for example (source):
- Calcium
- helps control the way other nutrients move through the plant and, in the form of calcium pectate, it binds cell walls together.
- Magnesium
- is used to make chlorophyll, so without it there's no photosynthesis. Like calcium, it helps glue cell walls together in the form of magnesium pectate.
- Sulphur
- is used by the plant to make certain amino acids and vitamins.
- Boron
- is used to form healthy plant cells, and is especially important for flowering.
- Copper
- is used in photosynthesis and in some enzyme processes.
- Iron
- is important in photosynthesis because it's used in chlorophyll production and the functioning of some enzymes.
- Manganese
- activates important enzymes in chlorophyll formation and respiration.
- Molybdenum
- is needed for the synthesis of amino acids using nitrates
- Zinc
- activates many enzymes and allows the plant to “read” its genetic code.
Inorganic fertilizers are produced by the chemical industry, they are very "pure" in the sense that they will probably not contain the extra nutrients listed above and also they are more concentrated and act more quickly. They are also more aggressive (see below). Organic fertilizers are probably better for your garden. They are slower too act (slow release), because their molecules have to be broken down by soil organisms before the nutrients within them are released for plant use. Examples of organic fertilisers include: seaweed, hoof & horn, dried blood, fish blood & bone, bone meal, poultry manure pellets and liquid comfrey or nettle feeds. These can be used either as top dressing, base dressing (before sowing or planting) or mixed in the soil.
A word of caution: too much fertilizer can damage plants and even kill good bugs like earthworms. This is specially true of inorganic fertilizers. Note that fertilizers do not improve the soil, but, when used correctly, they boost plant growth, improving health and providing more flowers or better crops.
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