The following is a list of vegetables and herbs that  you can plant in January in Sydney, a temperate zone. Just click on the name for the growing guide for each vegetable or herb:

• Amaranth
• Beans (dwarf and climbing)
• Beetroot
• Carrot
• Chives
• Cucumber
• Eggplant seedlings
• Kohlrabi
• Lettuce
• Marrow
• Mustard Greens
• Okra seedlings
• Parsley
• Radish
• Rosella
• Silverbeet
• Sunflower
• Sweet corn
• Turnip
• Zucchini

Plant of the Month – The stunning Crown of Thorns (Euphorbia milii ) 

The unusual and beautiful Crown of Thorns comes from the high regions of Madagascar where it grows on areas of rocky granite. If grown in the ground it can reach 1.5m tall with many branching stems.  In the home garden it is usually grown in pots. With correct light it can also be grown indoors.

Description:

The Crown of Thorns or Euphorbia milii is a slow growing, evergreen semi-succulent with thick fleshy grey stems covered in large spines about 1-1.5cm long projecting from the stems. The stems are adapted to water storage.

The intimidating stems are hidden by masses of fleshy, narrow, obovate, smooth-edged, green leaves that are spirally arranged on the stem that naturally drop off as the plant gets older.  It has small brightly coloured bracts in red, salmon, pink, orange, yellow, white and bicolours that grow in clusters off a stem.

The flowers of the Crown of Thorns are deceptive to the eye. What most would consider petals are in fact typical euphorbian inflorences or bracts called cyanthia (that look like petals); cup like structures from which the flowers emerge. They function to attract pollinators.  The five yellow nectar glands you can see are attached to the bracts. In the centre is the female flower with three styles surrounded by male flowers with a style each. (click on the image to see more detail)

Many cultivars have been developed that vary in size and colour. It is a pretty plant that flowers for most of the year with good care. The image below shows the size of the dwarf variety (yellow) and the colour variations available.

Aspect and Soil Conditions:

Select a sunny, site for crown-of-thorns. This plant will tolerate a few hours of shade during the hottest part of the day but does require sunshine for at least two-thirds of the day.

Hazard Warning:

When selecting a site also remember to place the plant in a safe place away from children and pets. All parts of the plant are toxic and poisonous to cats, dogs, horses, sheep and of course humans. The sap can be irritating to the skin and dangerous to eyes, causing burns and even blindness. Rinse the eye immediately with water should an accident happen. When handling the plant always wear thick gloves and protect the eyes by wearing protective goggles.

The Crown of Thorns can thrive in poor soil but it is important that the soil be free draining as it doesn’t tolerate wet soil at its rootball. If planted out in the garden, raise the bed to ensure best drainage.

Crown-of-thorns grows best in neutral or acidic soil, below 7.0, although slightly alkaline soil, slightly above 7.0, is acceptable.

If growing in pots, ensure that the potting mix is free draining such as 1/3 cactus mix with 1/3 coarse sand and 1/3 perlite. Make sure the pot has adequate drainage holes to allow the water to drain through easily. The pot should not be too big but rather just little wider than the root ball to make sure that damp does not accumulate to create problems of rotting and disease. Place a crock over drainage holes to allow water to drain off. Finally, place pot in a site that has good ventilation around it with not too much crowding from other plants.

Use an inorganic mulch such as gravel or stones, keeping them away from the stem.

Temperature:

A Crown of Thorns plant likes to be warm in temperatures between 15.6°- 35°C. It may lose leaves if the temperature goes below 10º C.  It is not frost tolerant so if winters are harsh it may be best to move potted plants indoors near sunny windows.

In the hot climate of Sydney’s summers, my plants stand against brick walls for stability and in extreme weather I use medium light coloured shade cloth over a sunny patio to protect my plants from being singed by heat whilst still allowing light in. They continue to flower and grow whilst not suffering the effects of 40ºC+ days. In winter the brick walls radiate warmth to the Crown of Thorns plants so that is another benefit.

Watering:

The Crown of Thorns is drought hardy and as mentioned above, the stems are adapted to water storage. Like all succulents they can die easily of root rot if overwatered. In fact, aside from proper light, correct watering is the most crucial part of caring for these plants.

It is essential to let the plant partially dry between waterings but not to let it dry out completely.  Neglect can see the stem shrivel, the leaves yellowing and slowing growth. Depending on the location and the heat experiened watering requirements may differ. As a rule of thumb, the Crown of Thorns should be watered deeply when the top 5cm are dry.

Water the pot until a little water comes out through the drain holes. When watering take care to direct water to the pot and not to get the leaves wet as they are prone to mildew with too much moisture. Never allow the pot to stand in a saucer of water.

If the pots are small and are able to be lifted safely, soaking the pots in a large basin as is done for other cacti and succulents is an ideal approach to deep watering. Then allow the pot to drain fully. Place pot in a site that has good ventilation around it.

The rule is to make sure pots used have good drainage and water deeply when the soil is dry to the touch just below the top few centimetres.

Restrict watering in winter to prevent leaf loss and the plant suffering.

The Crown of Thorns is very forgiving and it grows and flowers well with a sensible approach to watering.

Propagation:

Spring and summer are the best times to take cuttings of the Crown of Thorns.  Select an undamaged stem that is the thickness of a finger and about 5-10cm long with a flower bud at the top.

Use thick  gloves to protect your hands, long sleeves and goggles to protect from the toxic sap and thorns.

Take a clean, sterilised, sharp cutting knife and cut across the stem taking care with the thorns. You can uses a newspaper made into a cuff to handle the stem. Dip the cutting in lukewarm water to stop the sap running, then dip in powdered rooting hormone and set the cutting aside to dry for a few days.

Prepare a pot with a sandy propagating mix of cacti potting mix, sand and perlite. Press the dried off stem firmly down into the slightly moist propagating mix and allow to stand in a warm place out of direct sunlight.  Check the soil for drying and add a little water as required whilst not allowing the soil to dampen off.

It will take about 6-8 weeks for the roots to develop.

In Conclusion:

With care and properly located, the Euphorbia milii is a stunning, easy to maintain plant that mixes the dangers of its toxic parts and thorns with the attractive leaves and flowers. I have enjoyed watching them grow and admired their beauty, so if you have a safe space it is a drought tolerant plant for warm climates.

Below are more images of some of the different cultivars available. In fact there a many more. You can click on the images throughout the post to enlarge for more detail.