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.
Minor Nutrients
| Minor Elements (Macro Nutrients) | Functional Uses In Plant | Deficiency Symptoms |
|---|---|---|
| IRON (FE) | Formation of chlorophyll | Interveinal 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 plant | Tip growth die back and deformed buds |
| CHLORINE (CL) | Stimulates photosynthesis | Wilting but rare because present in water |
| COPPER (CU) | Formation of chlorophyll and converting sunlight into energy; also a fungicide | Leaf chlorosis and shoot tip growth die back |
| MOLYBDENUM (MO) | Helps production and use of nitrogen | Marginal and interveinal chlorosis of older leaves |
| ZINC (ZN) | Formation of growth hormones | Mottled leaf chlorosis, little leaves; Rosetting |
Major Nutrients
| Major Elements (Macro Nutrients) | Functional Uses In Plant | Deficiency Symptoms |
|---|---|---|
| NITROGEN (N) | Necessary for growth and development of green leaves and stems; component of most proteins | Chlorosis (yellowing) of older, lower leaves; stunting |
| PHOSPHORUS (P) | Promotes root growth and development; energy storage and transfer within plant | Purple like coloration; stunted root growth |
| POTASSIUM (K) | Improves cold hardiness, drought tolerance and disease resistance; promotes blooms | Poor flowering and fruit formation; brown leaf edges |
| SULPHUR (S) | Component of 3 proteins and 2B vitamins; flavor of onion, garlic, and mustard; a fungicide | Chlorosis of younger leaves; stunting |
| CALCIUM (CA) | Promotes cell division, strong cell walls, and sturdy structure | Collapse of cell walls and structural failure; curled leaf tips; stunting |
| MAGNESIUM (MG) | Component of chlorophyll; essential for photosynthesis | Marginal (edges) and interveinal (between veins) chlorosis of older leaves |
Plant Specific Nutrients
| Plant Type | Nutrients Needed | Some Recommended Fertilizers |
|---|---|---|
| ANNUALS | ||
| BEDDING OUT PLANTS | High 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 BASKETS | Treat 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 |
| SEEDLINGS/ TRANSPLANTS | High phosphorous for root growth; a root stimulant is often required | Water soluble: Plant-Prod 10-52-10 Liquid concentrate: Plant Starter 5-15-5 with rooting stimulant Granular: Bone Meal, Root Grow |
| VEGETABLES | Less 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 PLANTS | Only trace elements are required. | Pond tablets in the water at the rate of one per month will supply required. the necessary nutrients. |
| PERENNIALS | ||
| BULBS (SPRING & SUMMER) | 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 bulbs. |
| PERENNIALS | Need 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 |
| TRANSPLANTING | High phosphorous to promote root growth | Water soluble: Plant-Prod 10-52-10 Liquid concentrate: Plant Starter 5-15-5 with rooting stimulant Granular:Root Grow or Bone Meal, So-Green Super Phosphate |
| VINES | Require higher levels of phosphorous. | Water soluble: Miracle Gro, Plant-Prod Flowering Liquid concentrate: Alaska MorBloom Granular: So-Green Clematis & Vine, Bone Meal when planting |
| WINTERIZING | Never 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 |
| HOUSEPLANTS | ||
| FOLIAGE PLANTS | A balanced fertilizer | Water soluble: Schultz All Purpose, Plant-Prod All Purpose Liquid concentrate: Schultz All Purpose Slow release: Jobe’s Houseplant or Fern & Ivy Spikes |
| FLOWERING | A moderately high phosphorous level | Water soluble: Plant-Prod Flowering Liquid concentrate: Schultz All Purpose Slow release: Jobe’s Flowering Plant Spikes, Myke Indoor Plant |
| AFRICAN VIOLETS | Require phosphorous for bloom production | Liquid concentrate: African Violet |
| ORCHIDS | Water soluble: Orchid Food, Plant-Prod Orchid | |
| CACTUS | Cacti need less nitrogen | Liquid concentrate: Cactus Food |
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