How To Grow and Care For Gardenia Plants

The gardenia flower is a superb white flowering plant.  The scent of this beauty is incredibly captivating and inimitable. The Gardenia fills the air with its intoxicating, unmistakable fragrance from its beautiful waxy white flower. Myths abound on how difficult it is to grow Gardenias. Don’t be fooled!

The success of Gardenia care is enjoyed when its beautiful waxy white flower, fills the air with its intoxicating, unmistakable fragrance. Perfection in Nature!

The Name and Gardenia Varieties

The gardenia 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 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. It is also known as Gardenia Florida, grows up to 5 feet and has double flowers. Gardenia veitchii is a dwarf, small winter-flowering variety of Gardenia jasminoides which can be grown outside; the flowers are double.
• Gardenia augusta radicans is also a form of G. 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 and it’s nature at its finest. We have more on gardenia varieties.

Gardenia – Perennial or Houseplant

Most gardenias are hardy in zones 8-11, though a few varieties hardy to zone 7 have been developed (Kleim’s Hardy gardenia is one), and a few are only hardy in zones 10 and 11 (including Double Tahitian gardenia). So in northern hardiness zones, such as in Canada and northern states, indoor growth is the only option.

As perennials, gardenias can be grown outdoors as hedges, as specimen gardenia trees, or as potted plants in the garden. In addition, they can enjoy the almost ever-blooming gardenia flowers many days of the year.

Gardenia Care

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.

Gardenia Soil Mixture Important

The soil mixture is important for growing gardenias: avoid heavy, alkaline clay with poor drainage, and coarse, sandy soils. The best mixtures are equal parts of a fibrous loam, peatmoss 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.

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, that gardenias 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.

Give gardenias a location sheltered from wind but never plant them against, or close to stucco walls or fences where there is any chance of the stucco finishing being washed down by rain or the hose. This would add lime to the soil. 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 sun burns the flowers when it is too hot and when it is coupled with low humidity. A gardenia bush will benefit by syringing once or twice a day, except when they are in full bloom.

Soil and Water

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 barely moist. Too much moisture in the soil drives 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 high 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 leaves become smaller and turn yellow (chlorotic).

Planting In Pots or Tubs

If you plant 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 a gardenia tree… they produce real sweet fragrant flowering plants… a true show piece! 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.

Adjusting Soil For Gardenias Growing Location

Where azaleas and rhododendrons grow naturally, the soil will be acid enough for gardenias. For best results the soil pH should be between 5 and 6.

Where the soil needs more acidity, 1 ounce of iron sulphate 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 us 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.

Gardenia Plant Problems

We refer you to our sister article on gardenia plant problems.

Producing Abundance of Gardenia 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.

Blood meal, which contains principally nitrogen, is the first choice of fertilizer. Use a liberal tablespoonful to a gallon of water and let stand overnight. This amount is sufficient for an established growing plant. 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.

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.

Propagating Gardenias

Once you have your plants growing, they may be increased by taking tip 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 peatmoss or vermiculite. The humidity of the air should be between 70 and 80 per cent. They also should have bottom heat for quick rooting. Rooting hormone powders are a valuable aid in rooting cuttings, too.

Gardenia And Sooty Molds

Gardenias may be evergreen shrubs that flourish in a moist and well-drained soil. But, their fleshy foliage attracts feeding pests, often accompanied by sooty mold.

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 mold doesn’t affect or infect the gardenia 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

To treat sooty mold, you have to treat the source of the problem (plant scale) and control the scale insect on the gardenia excreting the honeydew. 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, neem plant oil insecticide or malathion.
Related Reading: What Causes Sticky Leaves On Plants?

Two Gardenia Care Videos