Gardenia Jasminoides


Gardenia jasminoides

If you're new to houseplants or lack confidence, Gardenia aren't the one for you. Not only do they require a LOT of maintenance, they'll award you with yellowing leaves and an absence of flowers if cultivated incorrectly. If you've just bought or received one of these beauties, have a read about how to offer the best care and how not to fall into the common traps...


Top Tips

  • Maintain evenly moist soil whilst in bloom, practicing the bottom-up method of irrigation.
  • High humidity is mandatory for Gardenia - do not situate it within three metres of an operating heat source as the risk of dehydration is high.
  • Bright, indirect light is best during the year's course, however, an hour or two of autumn & winter sunlight will bring great health.
  • Supplement fortnightly using a potassium-based feed whilst in bloom, reverting back to a general plant fertiliser at monthly intervals, soon after.
  • Scroll down to the 'Dormancy Care' section to learn about annualising blooms.
  • Repot ever three years using a houseplant compost during the spring months.

∙Water - 🔸🔸🔸

Firstly, a Gardenia isn't a fan of having dry feet - just a few days of drought will cause catastrophic damage for the rest of its life. Once the top quarter of the soil has dried out, rehydrate the soil using the bottom-up method to reduce the chance of fungal diseases associated with excess moisture on the foliage. Submerge the bottom quarter of the pot in a saucer of water until thorough absorption. Repeat this step weekly, especially with those grown in bright, warmer locations. Whilst the plant is in bloom, it's important not to use cold water as this will quickly shock the roots, causing multiple issues down the line. Under-watering symptoms include rapid flower or leaf loss and dry, sunken leaves or browning leaf patches; these issues are usually due to either forgetfulness, too much sunlight or too much heat. Over-watering symptoms include rotting lower leaves, yellowing leaves, a loss of buds or flowers, and root rot. Allow the majority of the soil to dry out in between waters, preventing a pool of standing water to accumulate beneath the pot. It's highly unlikely that you'll over-water a Gardenia due to their thirsty nature, but always be cautious of root rot if it stays in too saturated soil for extended periods of time. 


∙Humidity - 🔸🔸🔸

As high humidity is mandatory for all types of Gardenia, a weekly mist will help replicate its natural habitat in tropical Asia, preventing the browning of leaf-tips. If the plant is in bloom, be sure to use a humidity or pebble tray to counteract the dry air - click on this link to learn more. Do not mist the flowers as this will cause botrytis petal blight that can spread quickly if not dealt with accordingly. Never situate this plant within three metres of an operating radiator as it will cook both the plant and the surrounding air moisture, leaving you with a very unhappy specimen.


∙Location & Light - 🔸🔸🔸🔸

A location with a few hours of morning or evening sun is ideal for this species. Shady locations must be avoided at all costs due to the heightened chance of over-watering and root rot.

In terms of the ideal room around the house, on or within two metres of a north, east or west-facing window. Although situating a Gardenia in a south-facing window will provide a good amount of direct sunlight, you'll have to be very careful of sun-scorch. If the desired location melts a chocolate bar within half an hour, it'll be too much for the plant.


∙Fertilisation - 🔸🔸🔸

Use a fertiliser high in potassium to prolong its flowers during the festive period - an excellent example would be a Tomato Feed. Regular fertilisers, for instance, BabyBio or Miracle-Gro, will still do the job, but will favour foliar growth instead. For the rest of the year, a standard fertiliser can be used to supplement the plant to aid foliar and root growth. Once all of the flowers have elapsed, reduce supplements to every four to six weeks to allow the plant to regain its strength.


A developing bud that'll open in about ten days time, lasting up to two weeks.


Common Issues with Gardenia

Under-watering is the biggest issue when it comes to a Gardenia  Typical signs of this include wilting, sunken leaves, rapid flower or bud drop and stunted growth. Not only will you have to be mindful of persistent droughts, think about which plant parts to keep dry. Its foliage must also remain dry at all times to prevent the development of diseases and blights. Those situated in direct sunlight or within four metres of a radiator are more likely to suffer from under-watering related issues.

Too much sunlight will lead to sun scorch, with typical signs including browning or crispy leaves, dry leaf-edges, sunken leaves or stunted growth. Although too little light will cause over-watering issues, too much sunlight will be a detriment, too. Only allow up to five hours of direct sunlight a day, as the chance of cooking the foliage will become very high. If yours has fallen short of this, reduce the amount of sunlight to only an hour, and always be mindful of environmental shock (when too locations offer too different growing conditions). Remove some of the affected leaves and increase waters slightly.

Pests could also be an issue, most notably being whitefly and mealybugs. Especially before purchasing, have a quick scan over the plant's foliage and flowers, inspecting its cubbyholes for those white critters. If your specimen has fallen foul of pests, click on the appropriate links to learn more about treatment, as well as observing what they look like.

As mentioned before, powdery mildew and botrytis are major threats among heavy foliage plants due to the compact nature that aids the spread of the diseases. Watering above the foliage will allow excess moisture to sit in the cubbyholes of the stem, enticing harmful bacteria to thrive. Remove the affected areas and improve the growing conditions by situating the plant in a brighter location with the use of the bottom-up method of irrigation.

Never situate a Gardenia within four metres of an operating heat source, for instance a radiator or fireplace. Due to the heightened temperature, the plant will soak up far more moisture than those situated in cooler locations, increasing the chance of droughts and permanent damage. This species cannot cope with persistent dry soil - you're skating on thin ice if a Gardenia starts to wilt. 

Sudden flower loss can be caused by an array of different issues, including an change in location, too little hydration, too hot or cold temperatures or droughts and pests. Whilst the plant is in bloom, keep the soil evenly moist, to hydrate the thirsty work of producing flowers. Locations that are outside of the recommended temperature bracket, or have drastic fluctuations must also be kept off the cards, as Gardenia can be very sensitive to ambient change. The final issue could be to do with pests. Although it's highly unlikely that an infestation will cause a sudden change in health, have a quick inspection for whiteflyaphids, spider mite & mealybugs. For those that display signs of pest damage, click on the appropriate links or click here for more pests.

A lack of flowers is caused by a insufficient dormancy period, served in the winter months. Locations that offer near-similar temperatures all year round won't allow the plant to go dormant, resulting in poor spring growth. To achieve, situate in a location that dips to around 12°C  (54°F) with fewer waters. Allow the majority of the compost to dry out and provide a humidity tray while the radiators are operating.


The typical size of a Gardenia sold in garden centres. Maturity can be reached within five year, with the overall height only being 0.5m.


Dormancy Care & Annual Flowers

Trying to get a Gardenia to bloom again isn't the easiest of tasks, but those that have a cool room without artificial light at night in the winter months will be on the upper-hand. Repotting isn't usually mandatory if you want it to re-bloom - in fact, this may hurt the chances. Only repot every three years and after the blooming has finished. To get it to re-bud in the spring or summer, think back to its previous dormancy period served in the autumn and winter. The following steps should be done at the end of autumn, when a Gardenia enters its dormancy. 

Light

Be sure to provide a bright, sunny location with a few hours of direct light over the course of the year. In order for the Gardenia to fully become seasonised, avoid the use of artificial lighting during the winter months.

Hydration

Reduce irrigations so that around half of the soil becomes dry. Remember, they should only be watered from the bottom-up as rotting foliage are a common issue with cooler temperatures when saturated.

Occasional Feeds

While it's bloom, use a Tomato fertiliser to provide a nourishment of potassium. During the dormancy period, from late autumn to mid spring, only supplement once or twice to carry it through using a general houseplant fertiliser. 

Reduce Everything

This one is to remind you that everything needs to be reduced - especially the temperature.

Temperature

This is the most significant step - keep the temperature within 12 - 15℃  (54 - 59℉) throughout winter, until buds form in late spring. It'll be highly unlikely for a Gardenia to sufficiently bloom when the ambient temperatures are kept the same all year around, so we can't empathise the importance of temperature change!




Origins

Gardenia consists of 140 species with natural distributions across the world, most notably in Africa, Asia and many Pacific islands. The genus was described by Carl Linnaeus and John Ellis back in the mid eighteenth century, honouring Dr. Alexander Garden, a Scottish naturist at the time. The most popular Gardenia, the G. jasminoides, was brought over to England in 1761 from Eastern Asia. Georg Ehret queried whether the species was a Jasmine, later naming it in honour of the genus.


Temperature

8°C - 22°C   (46° - 72°F)
H1c - can be grown outdoors in spring and summer in a sheltered location, but is fine to remain indoors. If you decide to bring this houseplant outdoors, do not allow it to endure more than an hour of direct sunlight a day as this will burn the leaves. Regularly keep an eye out for pests, especially when retrieving the plant back indoors. 

Gardenia thrive in cooler locations and will generally flower better if a good dormancy is served in the winter when the temperature dips below 10°C  (50°F).


Spread

Up to 0.5m in height and width. The ultimate height will take between 4 - 6 years to achieve.


Pruning

Remove yellowed or dying leaves and plant debris to encourage better growth and improve the all-round appearance. Pruning must be done with clean scissors or shears to reduce the chance of bacterial and fungal diseases; remember to make clean incisions as too much damage can shock the plant.

Allow the flowers to fully elapse (usually in summer) before pruning the foliage back a third in time for their dormancy - this will promote vigorous new growth that'll house the future flowers.


Propagation

 Via seed or stem cuttings. To learn about the critical essentials with sowing seeds, be sure to click on this link - Seed Propagation Tips

For stem cuttings, use shoots that have a soft, bendy wooded base that haven't flowered; this propagation method can be taken in mid-spring. They should be at least 7cm in length and are found in the outer edge of the plant where the new growth takes place. Remove the lower half of the leaves, dip the wound in a rooting hormone and place in a well-draining potting mix - Seed & Cuttings Compost is advised. While the plantlet is still young, avoid direct sunlight or water-logging, and repot as necessary once the roots have surpassed 3cm in length. This method can be quite difficult, so be sure to take a few cuttings with differing variables to see which suits your skills the best.


Flowers

Gardenia flower between spring and summer if grown correctly with a good, cool dormancy in the winter months. Each individual flower will last up to two weeks, with the overall show lasting up to six weeks. Supplement the plant using a fertiliser high in potassium to prolong its flowers - Streptocarpus or Tomato feeds are an excellent choice. The Gardenia jasminoides is highly renowned for its oriental aroma and striking similarities to the true Jasmine.


Repotting

Repot every two or three years using Houseplant compost with added perlite or grit, during the spring and whilst the plant isn't in bloom. For matured specimens, introduce more grit to promote a stronger root ball as well as the reduction of potential root rot; click on this link for more information on how to perform the perfect transplant. Never repot whilst the plant is in bloom.


Diseases & Pests

Common diseases with Gardenia are root or crown rot, powdery mildew, leaf-spot disease, botrytis petal blight and powdery mildew. Keep an eye out for whitefly, spider mite, thrips, aphids & mealybugs. For more info on how to address any of these issues, hit this link.  Identifying Common Houseplant Pests & Diseases


Toxicity

Gardenia are considered slightly poisonous if consumed by pets and humans. If high quantities are eaten, it may result in vomiting, nausea and a loss of appetite.


Retail Locations

Some florists & Online Stores. Specimens are likely to be found in spring or summer at most garden centres. A small selection of Gardenia are sold during the festive period, but generally won't last as long as those sold earlier in the year. It's not advised to bring outdoor specimens inside as this could lead to environmental shock or the introduction of foreign pests into the home.

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