Fertilisers for succulent plants

Plants need at least thirteen elements from the soil for proper growth, in addition to carbon, hydrogen and oxygen which are obtained from air and water. Plants generally grow normally until they run out of one nutrient, which then limits growth. Deficiency or excess of nutrients often causes discoloured or deformed growth, which may be characteristic of that particular element, although there is a considerable overlap of symptoms.

Most succulent plants will grow better in the long term if additional nutrients are provided by application of fertilisers. Gross excess of some nutrients can induce deficiency of others. The moral is therefore to use balanced mixtures of nutrients in fertilisers, rather than applying a large amount of one element. Many fertiliser mixtures only specify their Nitrogen (N), Phosphorous (P) and Potassium (K) content on the label of the package, but unless especially pure ingredients were used in their manufacture, it is likely that some trace elements will be present fortuitously. Other fertilisers explicitly list their trace element content. The elements are identical whether inorganic or organic ingredients are used, but the source will affect the speed of their release and their availability.

Boron is the only element required by plants but with no function in animals, except that it may be toxic in excess. Borax is the active ingredient in some products designed to kill ants. In most cases, extreme measures have to be taken to induce boron deficiency in plants as such low levels are required. However, it has been suggested that cacti may benefit from higher levels of boron and some people add small amounts of borax when watering their cacti.

Silicon is also usually ignored as a micronutrient, and will be generally available in any gritty potting mixture suitable for cacti and succulent plants. However, significant amounts of silicon (as silica) may be present in plant tissues (especially in diatoms, grasses, sedges and horsetails) as a structural element. It must be translocated through the vascular system in solution and precipitated, often in crystalline form, under biochemical control to form precisely defined structures.

The N:P:K balance of some typical formulations are shown below, as quoted by the manufacturers, mainly using examples from the Chempack range which were readily available. This should not be taken as any special endorsement, as other brands will be equally suitable. I like to rotate between several brands to ensure a mix of micronutrients.
For succulent plants, a balanced NPK fertiliser such as Chempack No. 3 is suitable, but cactus growers may prefer a lower nitrogen content such as Chempack No. 8 to ensure that their plants remain compact. Chempak produce a specific cactus and succulent fertiliser with an even lower nitrogen content, in rather small packages. Leafy succulents such as Euphorbias may appreciate a high nitrogen boost (e.g. Chempack No. 2) in the Spring when they start growing, followed by the balanced mixture for the rest of the growing season. For comparison, a typical formulation to encourage tomatoes and other fruit has a very high Potash content as does Cactigrow.

Organic fertilisers may be mixed into a potting mixture for succulent plants when it is being mixed and provide sustained release of nutrients over a long time. The bulky constituents of organic fertilisers help to improve the soil structure. Many organic fertilisers contain essential trace elements and may also encourage beneficial soil micro-organisms. The role, if any, of beneficial mycorrhiza in the growth of succulent plants seems to be largely unknown, despite their demonstrated importance in culture of orchids and many woody plants. However, organic fertilisers will tend to encourage mycorrhyza in contrast to inorganic fertilisers which inhibit them.


Brand name	N : P : K	Comments

Cactigrow No longer available.	15 : 6.5 : 24.9	Trace elements: Boron 22mg/kg, Cobalt 16 mg/kg, Copper 16mg/kg, Iron 70mg/kg, Magnesium 120mg/kg, Manganese 42mg/kg, Molybdenum 14mg/kg, Zinc 14mg/kg Was sold at Holly Gate Cactus Nursery, West Sussex. UK.
Chempak Formula 2	25 : 15 : 15	High nitrogen boost for leafy succulents (e.g. Euphorbias) in the Spring.
Chempak Formula 3	20 : 20 : 20	Balanced general purpose feed - suitable for most houseplants.
Chempak Formula 8	12.5 : 25 : 25	Low nitrogen formulation - suitable for cacti.
Chempak Cactus & Succulent Fertiliser	8 : 34 : 32	Trace elements: Boron 44mg/kg, Copper 85mg/kg, Iron 168mg/kg, Magnesium 375mg/kg, Manganese 85mg/kg, Molybdenum 1.1mg/kg, Zinc 30mg/kg
Chempak tomato food	11 : 9 : 30	High potash formulation - may promote flowering / fruiting
Phostrogen	14 : 10 : 27	Trace elements: Boron 0.012%, Calcium 1.43%, Copper 0.0055%, Iron 0.04%, Magnesium 1.5%, Manganese 0.02%, Molybdenum 0.0016%, Sulphur 4.5%, Zinc 0.0055%
Phostrogen Tomato Food	12.5:5.0:24.5	Trace elements: Calcium 1.6%, Iron 0.4%, Magnesium 1.3%, Manganese 0.02%, Sulphur 8.6%

Organic fertilisers (typical values)

Pelleted chicken manure	6.0 : 5.0 : 3.0
Hoof and horn	13 : 0 : 0
Bone Meal	3.5 : 22 : 0
Seaweed meal	2.8 : 2.0 : 2.5
Well rotted manure	0.6 : 0.1 : 0.5
Well rotted compost	0.5 : 0.3 : 0.8	Free garden waste product - variable composition
Mushroom compost	0.7 : 0.7 : 0.3	Echevierias may dislike lime content
Wood ash	0.1 : 0.3 : 1.0	Traditional source of potash

The Elements Important to Plants
Macronutrients
Calcium	Ca	Major component of cell walls, important for root tips and growth. Deficiency: Poor root development with weak tips, distorted curled leaves with hooked tips. Excess: causes iron deficiency in sensitive plants.
Carbon	C	Major component of all organic compounds including carbohydrates such as starch and cellulose, fats and oils, proteins. Normally obtained from air. Deficiency: reduced growth rate. Excess: May be artificially increased in greenhouses to enhance growth of crops.
Magnesium	Mg	Essential for chlorophyll formation and a cofactor for many enzyme reactions. Deficiency: Leaf yellowing with brilliant colours. Excess: causes calcium deficiency.
Nitrogen	N	Essential for proper leaf and stem growth, protein synthesis. Deficiency: Reduced growth, pale yellow-green leaves starting with oldest. Excess: causes potassium deficiency.
Phosphorous	P	Important for germination and growth of seeds, growth of roots, flower and fruit production. Deficiency: Reduced growth, small bluish-green leaves becoming bronzy-purple or with scorched brown edges and falling off early, starting with the oldest. Excess: causes potassium deficiency.
Potassium	K	Promotes vigourous growth, disease resistance. Deficiency: Stunted growth with closely spaced leaves. Scorched brown leaf tips and edges, rolled edges starting with oldest. Excess: causes calcium and magnesium deficiency.
Sulphur	S	Essential for protein synthesis and chlorophyll formation. Deficiency: Slow growth with small, rounded brittle leaves.
Micronutrients - trace requirements only
Boron	B	Required for sugar transport, calcium metabolism, water regulation and reproductive functions. No known function in animals. Deficiency: Scorched, mottled discoloured and curled leaves, starting with most recent. Distorted and dead growing points, hollow stems, deformed fruit. Hard to achieve experimentally as requirements are tiny. Excess: scorched leaf edges (similar to potassium/magnesium deficiency).
Chlorine	Cl	Used to be thought to be metabolically irrelevant, but may affect carbohydrate metabolism and photosynthesis. Deficiency: stubby roots and wilting. Excess: scorched leaf edges (similar to potassium/magnesium deficiency).
Copper	Cu	Required for protein synthesis and reproductive functions. Deficiency: leaves become bluish-green, wither or remain folded. Yellow-edged tips of young leaves. Abnormal rosette formation at growing points. Excess: causes iron deficiency.
Iron	Fe	Required for chlorophyll formation and production of oxygen. Deficiency: Yellow leaves with green leaf veins, starting with most recent. May be caused by excess calcium. Excess: scorched leaf edges (similar to potassium/magnesium deficiency)
Manganese	Mn	Essential component of many enzymes and important for Chlorophyll formation. Deficiency: Yellow leaves with green veins, white or grey flecks, starting with oldest. Excess: causes iron deficiency and similar symptoms to manganese deficiency.
Molybdenum	Mo	Essential for nitrogenase (nitrogen fixing) enzymes and formation of root nodules in beans and peas. Deficiency: yellow mottling and dead spots on the leaves, distorted or dead growing points.
Zinc	Zn	required for synthesis of proteins and affects size and maturity Deficiency: Yellowing between leaf veins with purple/dead spots on the older leaves. Leaves small, deformed and closely spaced. Defective fruiting. Excess: causes iron deficiency.

The Fertiliser Page

Fertilisers for succulent plants