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.
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.
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.
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.
If you want to spread mulch around your gardenias, go for a woodchip or sawdust variety. This will also add acid to your soil to help growth.
Mulch around the base with organic mulch like bark chips, sugar cane or pea straw, keeping it away from the main stems of the plant.
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.
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.
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.
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.
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.
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.
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.
To revive your dying gardenias, remove them from the soil, amend the soil, replant them, and make sure that you water them correctly this time. You should prune your gardenias to help them grow bushy. To help drain water quickly from your gardenia pots, put stones in the pot before placing the soil or potting mix.
Phosphoric acid is the most acidifying phosphorus fertilizer. » Soil acidification due to use of sulfur fertilizers is also small compared to that attributed to nitrogen, due to the lower amounts of this nutrient used and the lower acidification per kg sulfur. Elemental sulfur is the most acidifying sulfur fertilizer.
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.
The best time of day to water gardenias is in the morning. If you're not sure what a good watering schedule looks like, it's usually around one-half cup of water every seven days or so. The soil needs to be moist but not saturated with moisture because if there are too many nutrients and they can lead to fungus growth!
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.
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.
Important note: Dynamic Lifter should not be used on Australian native plants that are sensitive to phosphorus.
Inhalation: Material may be an irritant to mucous membranes and respiratory tract. Skin contact: Repeated or prolonged skin contact may lead to irritation. Ingestion: Swallowing can result in nausea, vomiting and irritation of the gastrointestinal tract.
Apply Seasol regularly for several months before any fertilising is done. Once the tree is starting to respond to the Seasol treatment, apply an organic fertiliser such as Dynamic Lifter, blood and bone or slow-release tree tablets. Note: Sadly, some trees will be damaged beyond repair.