Fertilizers and Nutrients

Most commercial potting soils and soil-less mixtures are not very rich in nutrients. One way to give your plants a good start is to amend the commercial growing medium with compost, or other organic enrichments available at your garden store, in a ratio of three parts potting mixture to one part compost.

In a pot, you are responsible for providing all of the nutrients your plant needs to grow, so you will need to fertilize and add micro-nutrients on a regular basis. If you do not want to think about fertilizing, it is possible to add slow-release fertilizer pellets to the soil mix. Otherwise, a good quality water-soluble fertilizer should be used from time to time. Choose a “complete” fertilizer that provides the three basic nutrients needed by plants: nitrogen, phosphorus, and potassium. By law, fertilizers list three numbers representing the percentage of each of these nutrients in the mixture; for instance, 20-10-20 would be 20% nitrogen, 10% phosphorus, and 20% potassium. The rest of the fertilizer is filler.

Plants which do not have access to these basic nutrients will not thrive, and you cannot rely on standard potting soils or soil-less mediums to provide them. The main symptoms which may indicate a nutrient deficiency are listed on the next page. Choosing a complete fertilizer will address all of these weaknesses. Apply the fertilizer according to the directions on the package, paying special attention to whether the solution should go on the leaves (foliar fertilizer) or just into the soil. Apply fertilizer in small amounts, regularly, as large quantities of fertilizer have the potential to burn plants and are largely lost through run-off anyway.

Fertilizer and Nutrients

Minor Nutrients

Minor Elements
(Macro Nutrients)
Functional Uses In PlantDeficiency Symptoms
IRON (FE)Formation of chlorophyllInterveinal chlorosis of younger leaves
MANGANESE (MN)Helps in uptake of carbon dioxide which is used for photosynthesis.Mottled interveinal chlorosis of leaves
BORON (B)Development of shoot tips and leaf bud; formation and movement of sugars in plantTip growth die back and deformed buds
CHLORINE (CL)Stimulates photosynthesisWilting but rare because present in water
COPPER (CU)Formation of chlorophyll and converting sunlight into energy; also a fungicideLeaf chlorosis and shoot tip growth die back
MOLYBDENUM (MO)Helps production and use of nitrogenMarginal and interveinal chlorosis of older leaves
ZINC (ZN)Formation of growth hormonesMottled leaf chlorosis, little leaves; Rosetting

Major Nutrients

Major Elements
(Macro Nutrients)
Functional Uses In PlantDeficiency Symptoms
NITROGEN (N)Necessary for growth and development of green leaves and stems; component of most proteinsChlorosis (yellowing) of older, lower leaves; stunting
PHOSPHORUS (P)Promotes root growth and development; energy storage and transfer within plantPurple like coloration; stunted root growth
POTASSIUM (K)Improves cold hardiness, drought tolerance and disease resistance; promotes bloomsPoor flowering and fruit formation; brown leaf
SULPHUR (S)Component of 3 proteins and 2B vitamins; flavor of onion, garlic, and mustard; a fungicideChlorosis of younger leaves; stunting
CALCIUM (CA)Promotes cell division, strong cell walls, and sturdy structureCollapse of cell walls and structural failure; curled
leaf tips; stunting
MAGNESIUM (MG)Component of chlorophyll; essential for photosynthesisMarginal (edges) and interveinal (between veins) chlorosis of older leaves

Plant Specific Nutrients

Plant TypeNutrients NeededSome Recommended Fertilizers
BEDDING OUT PLANTSHigh phosphorous to promote flowering.Water soluble powder: Miracle Gro, Plant-Prod Flowering
promote flowering.
Liquid concentrate: Alaska MorBloom
Granular: So-Green Rose and Flower, Smartcote Annual Food
HANGING BASKETSTreat as a bedding out plant or use slow release fertilizer in the soil.Water soluble/liquid concentrate: see ‘Bedding Out Plants’
Granular: Smartcote Hanging Basket Food
Other: Jobe’s Plant Spikes
High phosphorous for root growth; a root stimulant is often requiredWater soluble: Plant-Prod 10-52-10
Liquid concentrate: Plant Starter 5-15-5 with rooting stimulant
Granular: Bone Meal, Root Grow
VEGETABLESLess emphasis on nitrogen except for leafy vegetables.Water soluble: Plant-Prod Tomato & Vegetable
Liquid concentrate: Schultz Tomato Food
Granular: So-Green Garden Food or Tomato Food, Vigioro Pink
All Purpose
WATER PLANTSOnly trace elements are required.Pond tablets in the water at the rate of one per month will
supply required. the necessary nutrients.
Relatively high phosphorous fertilizer to encourage roots & flowers.Water soluble: Plant-Prod Flowering, Miracle Gro
Granular: Bone Meal
Note: Bloodmeal helps keep some squirrels from feeding on
PERENNIALSNeed phosphorous for a strong root system and potassium for healthy growth.Water soluble: Plant-Prod Flowering, Miracle Gro
Liquid concentrate: Alaska MorBloom, Shultz All Purpose
Granular: Bonemeal, So-Green Perennial Food, Smarcote
Perennial, Miracle Gro Shake-n-Feed
TRANSPLANTINGHigh phosphorous to promote root
Water soluble: Plant-Prod 10-52-10
Liquid concentrate: Plant Starter 5-15-5 with rooting
Granular:Root Grow or Bone Meal, So-Green Super
VINESRequire higher levels of phosphorous.Water soluble: Miracle Gro, Plant-Prod Flowering
Liquid concentrate: Alaska MorBloom
Granular: So-Green Clematis & Vine, Bone Meal when planting
WINTERIZINGNever add nitrogen in fall as it encourages excess leafy growth.A fertilizer without nitrogen will strengthen plants for better
winter survival: Alaska MorBloom, So-Green Muriate of Potash
FOLIAGE PLANTSA balanced fertilizerWater soluble: Schultz All Purpose, Plant-Prod All Purpose
Liquid concentrate: Schultz All Purpose
Slow release: Jobe’s Houseplant or Fern & Ivy Spikes
FLOWERINGA moderately high phosphorous levelWater soluble: Plant-Prod Flowering
Liquid concentrate: Schultz All Purpose
Slow release: Jobe’s Flowering Plant Spikes, Myke Indoor
AFRICAN VIOLETSRequire phosphorous for bloom
Liquid concentrate: African Violet
ORCHIDSWater soluble: Orchid Food, Plant-Prod Orchid
CACTUSCacti need less nitrogenLiquid concentrate: Cactus Food