I first started to learn about gardenia plant care over 45 years ago. At the time I worked at an orchid nursery.
Across the street, Mr. Landrum grew thousands of grafted avocado, mango trees, and gardenia bushes. The gardenia was grafted on Gardenia thunbergia rootstock.
Old Mr. Landrum planted all his trees in gallon cans, set on bricks. He even made his own grafting knife from a hacksaw blade and a piece of conduit.
Oh, how I wish I still had the one his son gave me. That is where my first experience with the gardenia know as “Miami Supreme” began.
Great Gardenia plant care produces “Perfection in Nature!”
It happens when the beautiful waxy white fragrant flowers of the Gardenia plant fills the air with its intoxicating, unmistakable fragrance.
Myths abound on how difficult it is to grow Gardenias. Don’t be fooled!
We’ve put together a “how to” on growing and caring for gardenias. Soil, planting, pH and some video.
Do you find caring for Gardenias difficult? Let’s help demystify the myths of how to grow these acid-loving plants called Gardenias.
Gardenia Location An Blooming Advantage
Those who love the Gardenia and live in mild climates such as the southern part of California and warm southeastern states are fortunate indeed!
With little trouble, they can grow gardenias outdoors as hedges, as a specimen gardenia tree or as potted plants in the garden.
In addition, they can enjoy the almost ever-blooming gardenia flowers many days of the year.
How To Care For Gardenias
Gardenias will live for many years when given proper care. Although they are critical of a few things.
They are as easy to grow as roses once their requirements are understood.
It is best to start with young plants in spring or early summer.
One or two-year-old plants give the most blooms. Depending on climate and variety, flower buds may be had in May but the bulk of bloom will be in July and August with a few stragglers in December.
Gardenia Soil Mixture Important
The soil mixture is important for growing gardenias. They are acid-loving plants. Avoid heavy, alkaline clay with poor drainage, and coarse, sandy soils.
Related: What Is The Best Gardenia Soil?
The best mixtures are equal parts of a fibrous loam, peatmoss (or organic matter) and well-decayed manure, or one part each of loam, leafmold and well-decayed manure.
In loam or sandy soil, dig a hole about a foot deep and 2′ feet wide and fill with the soil mixture.
Where the soil is composed of heavy clay, dig a larger hole and use some coarse sand along with the above mixture.
Some growers also feel that in a heavy clay we should dig a hole about 3′ feet deep and fill the bottom foot with broken rock or gravel to give additional drainage.
Gardenia Care – Planting & Location
When planting, do not set the plants deeper than they were when originally planted. Gardenias resent being planted too deeply.
Bear in mind, too, when caring for gardenias they like plenty of root space and do best planted far apart and away from large shrubs.
Since they are surface rooting – annuals, perennials or ground covers should not be planted around them.
Gardenias need a location sheltered from the wind and never plant them against, or close to stucco walls or fences where there is a chance of the stucco finishing being washed down by rain or the hose. This would add lime to the soil. Not good for acid-loving plants.
The ideal location would be at the south side of a house, preferably where there is light shade in midsummer between the hours of 11 A.M. and 2 P.M.
The full sun burns the flowers when it is too hot and when coupled with low humidity.
A gardenia bush will benefit by syringing once or twice a day, except when they are in full bloom.
Since gardenia plants are native to tropical China where the atmosphere is warm and moist and naturally have acidic soil, we should try to duplicate these conditions in growing them.
Keep the soil moist. Too much moisture in the soil dries out the air and allows fungi to attack the roots. The dark green leaves may become yellow (chlorotic) and the plant may die.
Gardenias like humidity and all possible heat at the roots.
A mulch helps create humidity but often keeps the roots too cool. (It is surprising that the plants will stand 20° without damage; some varieties do not suffer at 15°.)
Whether to mulch or not will depend upon your climate. Where humidity is low a mulch is often helpful; where humidity is high a mulch may keep the roots too cool. When the soil is below 50° for any period of time the green leaves become smaller and turn yellow (chlorotic).
Growing Gardenias In Pots or Tubs
If growing gardenias in a tub or box, use a large container as gardenias do not like their roots crowded.
If you go the potted plant or tubbed route consider the Everblooming Gardenia Tree sold by Monrovia… they produce real sweet fragrant flowers… a true showpiece!
They make a wonderful potted plant for the pool, patio or deck area.
With the plants in containers, you have an added advantage that they can be brought into a warm and sheltered place during severe winter weather.
Gardenias can be planted out in the garden from the containers at any time, but the best time is in spring and early summer.
When transplanting, be sure to keep the roots moist and covered. Disturb them as little as possible.
Gardenias Growing Location Adjusting Soil For Acid-Loving Plants
Where acid-loving plants like azaleas and rhododendrons grow naturally, the soil will be acid enough for gardenias.
In many parts of the eastern United States the soil is perfectly suitable, but where this condition does not exist, or where the water is alkaline, corrective measures must be taken.
For best results, the soil pH should be between 5 and 6.
Where the soil needs more acidity, 1 ounce of iron sulfate to a gallon of water should be poured around the plant when necessary.
Soil sulphur may be worked into the soil at planting time, or in the top 1/2 inch of soil after planting; it is safe, but slow acting, taking about two or three months.
Symptoms of Too Acid / Too Alkaline Soil pH
A careful check of the soil acidity with a soil test should be made before using aluminum or iron sulphates as there is always the danger of burning the roots.
This shows up in a browning of the leaves, beginning at the tips, and the eventual loss of foliage.
When the soil is too acid. below pH 4.5, bud drop occurs since both iron and aluminum become too soluble and poisonous.
When the soil is alkaline, above pH 7, the leaves become chlorotic. Large amounts of organic matter such as peat will help keep the soil acid.
There are only a few soils in the United States so deficient in calcium that gardenias will not grow well. This deficiency causes the terminal buds to die as soon as they grow.
Gypsum added to the soil will rectify this condition, but first, consult your county agricultural agent for the amount needed and how to apply it.
The Right Gardenia Fertilizer Helps Produce An Abundance of Flowers
This evergreen shrub produces an abundance of fragrant flowers, the plants will need a liberal feeding of nitrogen and a moderate amount of potash and phosphorus; the latter two will be found sufficient in most soils.
Use a liberal tablespoonful to a gallon of water and let stand overnight. This amount is sufficient for an established growing plant.
An application should be made once a month during the growing season from April to October. Do not add any calcium to the soil unless it is known to be absolutely devoid of it.
Gardenias are nitrogen and iron-hungry plants and calcium ties these elements up, making them insoluble and causing the leaves to become chlorotic.
Learn more about: Yellow Leaves on Gardenia – Causes | Treatments | Prevention Tips
A chemical combination that has proven successful is a level tablespoonful each of ammonium phosphate and potassium sulphate to a gallon of water to make a foliar feed.
This supplies all three – NPK – nitrogen, phosphorus and potash. Pour a half-gallon around each plant every two or three weeks during the growing season.
Or, you may alternate by using ammonium sulphate at the rate of one level tablespoonful to one gallon of water. This supplies nitrogen and sulphur and leaves the soil acid. Do not use superphosphate as it contains calcium.
Cottonseed meal or a commercial organic liquid acid fertilizer may also be used. It is best to feed little but often, as overfeeding may cause bud drop.
Do not feed in winter and do not use sodium nitrate on gardenias as it has an alkalizing effect.
Growing Gardenia Indoors Breaking the Rules
Who would not enjoy the intoxicating fragrant gardenia blossom indoors? But can gardenia grow indoors?
How do you care for a gardenia plant indoors?
As with most plants, some have difficulty properly caring for gardenias indoors and others experience great success.
Most articles I’ve read on growing a gardenia bush in the home seems to discourage the reader. Don’t believe everything you read. You’ll hear statements like:
- You cannot have a large, flourishing gardenia plant without a southern exposure.
- The flower buds will fall off before they open
- A gardenia needs sun, but not full sun indoors.
- The plant must have high humidity
- Your plant will always be infested with mealy bugs.
By the time you’ve read that much, you’ve decided your gardenia is your enemy and in need of rescue.
How To Care For A Gardenia Plant Indoors
If you keep your gardenia outdoors, before the night temperatures drop much below 55° degrees Fahrenheit, bring the plant indoors.
How much sun do gardenias need? Read our article on Gardenia Sun Requirements.
Place your potted gardenia in a shallow pan or saucer in a location where the plant will get plenty of light but little or no direct sunlight.
When new growth starts, feed weekly with an acid fertilizer, mist the leaves daily and watch for insects, spraying as necessary.
An occasional or even weekly washing of the leaves with a soft spray of tepid water seems very beneficial to gardenias.
Keep the soil moist but never allow water to sit and accumulate in the saucer.
If the old leaves begin to turn yellow or the new ones whitish, the plant may be too wet or be in need of more acid conditions. Remember, gardenias are acid-loving plants.
Gardenias grow best in a soil with a pH of 5.0 to 5.5. “Acid” can be provided, only if necessary, by the addition of 1/2 teaspoon of sulphur sprinkled on the soil and dampened.
Protect the plant from drafts, and feed until buds are well matured.
Blooming usually occurs indoors in late winter, but may begin as early as late December and progress until summer.
After all danger of frost is over, remove the plant gently from the pot and examine to determine whether it is pot-bound.
Repot, if necessary using an azalea soil mix.
Video: Creating A Gardenia Bonsai Tree
When to plant gardenias?
Once you have your plants growing, they may be increased by taking gardenia cuttings about 3″ to 5″ inches long from fairly mature wood during the Winter months. Place these in an acid medium such as sand and peat moss or vermiculite.
The humidity of the air should be between 70 and 80 percent. They also should have bottom heat for quick rooting. Rooting hormone powders are a valuable aid in rooting cuttings, too.
Gardenia And Sooty Molds
Gardenia trees may be evergreen shrubs that flourish in a moist and well-drained soil. But, their fleshy foliage attracts feeding pests, often accompanied by sooty black mold.
Related: More on Gardenia Diseases
What Causes Sooty Mold?
The feeding insects suck on sap and secret what is called “honeydew.” The honeydew is scattered on the surfaces of the gardenia’s leaves, blooms, and stems.
Sooty mold looks just like the name implies… the plant leaves, twigs or branches will be covered in filthy, black soot. You might even think that someone has spilled ashes on your plants.
Effects of Sooty Mold on Gardenia plants
The sooty black mold doesn’t affect or infect the gardenia hedge directly. It is the moldy layer formed across the honeydew that prevents air and light from reaching the gardenia.
The lack of air and sunlight inhibits the gardenia’s ability to carry out the process of photosynthesis, which results in stunted growth and dieback.
Treating the Sooty Mold
You can wipe the plant surface using a clean cloth, water, and soap. However, if it’s a severe infection you have to treat the problem in a more aggressive way, using a horticultural oil, insecticidal soap, neem plant oil insecticide or malathion.
Related Reading: What Causes Sticky Leaves On Plants?
The Name and Gardenia Varieties
The gardenia shrub was named in honor of Dr. Alexander Garden and is a member of the madder family, not the jasmine plant family.
There are several species and varieties of Gardenia suitable for outside planting. Gardenia jasminoides (Gardenia grandiflora), or its near variety, Mystery, is a plant ordinarily up to 3′ feet in size and is very popular for outside planting.
Related: Cape Jasmine Growing and Care (Gardenia jasminoides)
Gardenia jasminoides, also known as Gardenia Florida, grows up to 5′ feet and has double flowers. Gardenia veitchii is a dwarf (dwarf gardenias), small winter-flowering variety of Gardenia jasminoides which can be grown outside; the flowers are double.
Gardenia augusta radicans is also a form of Gardenia jasminoides; it is a small plant, 12″ to 18″ inches tall, with small, double and highly perfumed flowers.
Gardenia brighamii – is a small tree which can reach at height of 15′ feet. Gardenia brighamii growing this size is rarely seen. It naturally grows in dry forests of Hawaii.
Gardenia taitensis – known as the Tahitian Gardenia, has large, pinwheel-shaped, single blooms with a sweet fragrance. Needs full sun and warm temperatures for best results.
On its own the gardenia plant is beautiful, add in the flowers with their intoxicating, fragrance, its nature at its finest.
Answer: Kansas Citians who see this will smile because in the lobby of my office is a gardenia plant nine feet high and eight feet wide.
Take tip cuttings that are three or four joints long, strip off the bottom pair of leaves, dip the cut end in Rootone, and set the cuttings in perlite or a mixture of perlite and peat moss.
You must have bottom heat and you must keep the rooting medium on the acid side for best results. Cuttings do best from December to March, but I have rooted them all year round.