Gardenias prefer a rich, moist soil that is slightly acidic. The soil must also be free draining as they will not tolerate waterlogging. If your soil is of poor quality then work in some compost and cow manure before planting. Apply gypsum to improve drainage in clay soils.
A well-draining, peat-based potting mix will make your Gardenia happy. They enjoy nutrient rich soil, so adding organic matter (like peat moss) to your potting mix is very important. To make sure your soil will drain well, mix in orchid bark, charcoal, or perlite.
Gardenias use a lot of nutrients to produce so many glorious blossoms. Feed your shrubs by applying an acidic, slow-release fertilizer such as an azalea or camellia fertilizer. For the organic gardener, blood meal, fish emulsion or bone meal work well.
Nitrogen deficiency shows as yellow between the veins at any time through the year. Aged fowl manure or Blood and bone meal applied at one handful per square metre and watered in well every eight weeks from Spring through Summer will address this deficiency.
Feeding and mulching Gardenias are fed during the growing season from spring to autumn with a complete fertiliser such as Seasol plus Nutrients Roses & Flowers. Water it in well after application. Plants also benefit from liquid feed such as PowerFeed PRO SERIES for Roses & Flowers during the growing season.
The thinking behind this practice is that the yellow leaves are a sign of magnesium deficiency. Adding Epsom salts, or magnesium sulfate, is supposed to replenish the missing magnesium, perking up the gardenia in the process. Some gardeners recommend a one-off dosing, others a feed at regular intervals.
Gardenias, along with roses, palms and podocarpus, need lots of magnesium. When the nutrient is in short supply, the older leaves turn yellow. Give the plant a boost (and maybe return some green to yellow leaves) by applying magnesium sulfate or Epsom salts.
It affects a range of plants including gardenias, rhododendrons, azaleas, camellias, roses and citrus. The solution is to get some Epsom salts. Take half a litre of water, and put in half a teaspoon of Epsom salts, then shake and stir. Either water it on plants or you can foliar spray it.
Because gardenias need all three essential macro-nutrients (nitrogen, phosphorus, potassium) and also a good dose of micro-nutrients such as iron and manganese, you should feed them with an organic fertiliser such as Dynamic Lifter. Do this every two to three months from spring through to autumn.
Are Coffee Grounds Good for Gardenias? Don't worry about adding more coffee grounds to your gardenia soil; these flowers absolutely love coffee. In addition to being an excellent source of nitrogen, the acid in coffee lowers the pH of the surrounding soil, stimulating the roots of acid-loving plants such as gardenias.
Osmocote is one of the most popular and well-respected fertilizer brands and when it comes to gardenia fertilizers you can't go wrong with this plant food. What you'll love about this product is that it is easy for beginner gardenia gardeners. All you need to do is apply it once every 6 months.
Though vinegar can be fatal to many common plants, others, like rhododendrons, hydrangeas and gardenias, thrive on acidity which makes a bit of vinegar the best pick-me-up. Combine one cup of plain white vinegar with a gallon of water and use the next time you water these plants to see some amazing results.
Choosing a good quality potting mix that drains well is the best way to grow gardenias in a pot. Gardenias do prefer an acidic soil from about 5 to 6.5. You can use a specialty product labeled for gardenias, but most potting mixes are slightly acidic so a general potting medium is all you need.
In addition to amending the soil with compost or aged manure, these acid-loving plants will appreciate coffee grounds, tea bags, wood ashes, or Epsom salts mixed into the soil as well. Since they are rich in nitrogen, magnesium, and potassium, coffee grounds are oftentimes a more favorable homemade gardenia fertilizer.
To acidify soil around the shallow roots of the plant, organic gardener Howard Garrett advises mixing one tablespoon of vinegar per gallon of water every time you irrigate the plant. While watering gardenias with a vinegar solution can lower the soil's pH level, the effects are short-lived.
Low on Magnesium
If your gardenia needs magnesium, this will cause the leaves to turn yellow. You can remedy this with a fertilizer high in magnesium, or you can add some Epsom salts to your soil. Mix one teaspoon to one gallon of water and apply every two to four weeks.
Young gardenia leaves turning yellow is likely from low iron. All can be fixed by giving your gardenia a dose of an acidic nitrogen fertilizer containing micronutrients. Once your gardenia leaves are green again, use the fertilizer twice a month from early spring to late summer.
Leaves that yellow in the spring may be a symptom of iron deficiency. Consider leaving them on the plant rather than cutting them, as cutting may also remove flower buds. Instead, fertilize your gardenia with an iron-rich fertilizer.
The yellowing is caused by a lack of magnesium. We suggest feeding with Tui Enrich Rose, Camellia, Azalea & Gardenia controlled release fertiliser in early spring and late summer, and applying Tui Organic Seaweed Plant Tonic regularly. Epsom salts will also help when there is a lack of magnesium.
Plants like azaleas, gardenias and blueberry bushes need acidic soil to thrive, that's why ACV with 5 percent acidity works well as a fertilizer for certain flora.
Fertilize Gardenias every 2-4 weeks during their growing season (March to October) with a dilute fertilizer for acid-loving plants. Do not fertilize from November to February. Cut off the faded Gardenia flowers, just below the leaf node, to encourage continuous blooming.
Spraying your gardenia with an antifungal agent (such as horticultural oil with baking soda and insecticidal soap) can reduce the risk of infection or infestation.