What to Plant in December

Today is the first day of summer and this is the first planting guide of the season.

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

Plant of the Month – Philodendron hastatum (Silver sword)

Sometimes plants that we have taken for granted give us a lovely surprise.

So it was with our Philodendron hastatum. It had been given to us by a friend as a small climbing plant, the one in the image below, about 5 years ago. We didn’t even know what kind of plant it was. It grew happily outside on the shady side of our verandah, just one potted plant amongst the many, and to be honest, a little overlooked amongst the more showy plants around it..

After having been forced into Covid lockdown in another state for 2 years, I didn’t recognise it when I returned for it had changed completely.

In place of the small ovate leaves of the juvenile plant, were large sword shaped leaves and two interesting growths appeared on the petioles, or leaf stalk of two of the leaves.

To my utter amazement two beautiful flower like inflorescences grew and unfurled one at a time over couple of days and having done some research, I came to understand what an amazing plant the Philodendron hastatum really is.

Today I share some of the images with you and also information about it and its beautiful inflorescences.

Click on any image in this post to see further details.

(Please note that all the images on this post are copyright)

Juvenile plant with smaller leaves growing in a terracotta pot.

Philodendron hastatum is an aroid and member of the Araceae family. It is found endemically in the humid forests of southeastern Brazil. and in states of Minas Gerais and Rio de Janeiro the plant grows in its natural habitat.

The greyish green stem, 2-3cm in diameter with flaking outer layers is the central support of the  plant and divided by nodes and the stem sections or internodes 2-10cm long. Higher up the plant the stem is greener and thicker.

The originating part of the stem showing the nodes and internodes.

The nodes produce a leaf that comprises a blade and petiole (leaf stalk)and also produces aerial roots. This is also the site of the buds that can later develop as the plant matures. See the image below, where you can see a mature root as well as emergent roots and where the petiole has emerged at the node too.

The newer part of the stem with nodes developing and the stalk or petioles of the leaves and a mature aerial root.

These aerial roots will anchor the plant to a tree, rock or the ground where it can creep across the soil in its juvenile form.

The erect, spreading leaves arise from the nodes on the stem and grow outwards, moving towards the light. They emerge from protective bracts or modified leaves called cataphylls that are 20- 46 cm long. The leaf extends from petioles that are about 45cm long. 

The petiole is flattened toward the upper side of the leaf and rounded below as can be seen in the image below. This gives it more flexibility. Also seen in this image is how the petioles are emerging from a nodes on the stem along with roots.

The petiole arising from the stem.

The leaves of philodendron hastatus as the name suggests, are are “hastate” which means having a narrow triangular shape like that of a spearhead.

The sword shaped leaves of the mature plant are elongated, ovate- triangular with two lobes at the base and coming to a point at the apex. In fact the tip is curved downward like many forest plants to direct rain downwards.

The leaves can range in size from 20-60c m long and 10-30 cm wide.

They are a unique silver-grey green in colour with a slight sheen on their upper surface and are paler underneath. Details of the veins can be seen in the images of leaves on this post.

The main veins can be seen to be concave on the upper surface whilst being a thicker convex ridge on the underside of the leaf. the other veins are fine and close together.

The juvenile ovate leaves of the plant, shown below, are on cylindrical dark green stems which have longer internodes of 5cm. Below are two images showing the differences in shape between the juvenile and mature leaves. There is also a great size differential.

Smaller leaves of the young Silver sword plant.
The mature leaves of the Silver sword

To understand why the Philodendron hastatum has this variability of leaves over its lifetime it is important to go back to its native growing conditions.

It is native to the humid rainforests of Brazil and Colombia where the humidity and rainfall is high. The plant begins its life in the dark and dimly lit under storey of the forest and unlike plants that seek out light, Silver Sword, by the process of skototropism does the opposite It elongates on the side not receiving sunlight thereby growing toward the darkest places like that at the foot of a tree. On its own it is unable to reach the light in the upper storey but seeking out tall trees and being hemi-epiphytic it can now climb to better better lit parts of the canopy. It then develops larger leaves more suited to do this. This is actually an adaptation that allows this climber to survive.

My little plant tried desperately to find something upon which to climb but 5 years ago we knew nothing about this and so it remained amongst similar sized pots and in its juvenile state.

Additionally, Sydney was going through drier conditions, also so different from those of a rainforest where the plant would always be in wet and humid conditions. In fact, In 2019 conditions were drier and hotter than any other NSW drought in the last 120 years. From January 2017 to December 2019, rainfall was the lowest on record. The 2017, 2018, 2019 and 2020 calendar years were among the warmest on record.

Two factors were in our favour. The site in which the pot was situated was brightly lit (south facing in the southern hemisphere)with the plant not receiving full sunlight to its leaves, which it hates. The light in a rainforest is more dappled, and fortuitously it was planted in a terracotta pot which breathes, preventing root rot. Watering was hit and miss but it must have been enough because the plant survived.

The turning point for our little plant seems to have been the extremely wet conditions in Sydney over the past two years. Now we had light, humidity and plenty of natural precipitation, instead of needing to use town water which has chemicals.

It appears that the change in conditions allowed the Philodendron to “flower” and provided us a most spectacular, if brief, insight into the full life of the plant as would happen in its natural state. Through the happy coincidences of nature, this somewhat neglected plant decided it was time to shine.

Two inflorescences, one open and the other still closed.

What looks like a flower is actually an inflorescence, or a modified leaf called a spathe, that protects the reproductive part of the the plant, the thickened spike, or spadix where the true flowers are located.

The spathe emerges from the petiole that supports the leaf blade. In this case two spathes emerged in the petioles of the newest leaves adjacent to each other on the stem. They opened one after another.

On the end of the stem a new leaf was forming, enclosed by a covering bract called cataphyll, between the adjacent leaves.

Below is an image of the light green spathe with its creamy interior and the spadix with three distinct zones. From the bottom of the spadix: the lowest zone are the female flowers (just barely seen), then a small ring of infertile male flowers and at the top end the male flowers. Though it is hard to see with the naked eye, each tiny flower is supported on a tiny stalk.

The beautiful fully open Silver sword inflorescence.

These are the male flowers. This upper part of the spathe is called the blade. The heavy ring at the bottom comprises the sterile male flowers which emit a pheromone that attracts pollinators .

The male flowers on the spadix. The infertile ring of flowers at the lower part of the blade.

Below the blade portion of the spathe hidden in the floral chamber are the female flowers that are just visible in the image below.

Looking down into the flower chamber and the female flowers.

In their native rainforests the Philodendron hastatum are pollinated by specialised scarab beetles that are attracted to the inflorescence by the pheramones released that can spread 200m on forest winds. These are emitted at dusk and in the evening. It is released through the process of thermogenisis. The increased temperature in the spadix is caused through the through the release of salicylic acid. The pheramone is released in waves as the reproductive phases of the plant take place, optimising the plant’s opportunity for pollination. The beetles follow the scent to its source.

During the male and female anthesis ( reproductive action) the spathe opens to allow the beetles to come to feed and to reproduce themselves in a safe environment. They come in contact with the resins present in the spadix and collect pollen and then carry it to another bloom at female anthesis.

In addition, the beetles are drawn to the inflorescence by the internal heat produced by the plant which can even be felt by the human hand and can be as hot as 12C above the ambient forest temperature of 25C and can be as much as 20C. This makes the spadix visible on infrared thermal imaging.

An interesting point for us was that during the opening of the inflorescences we did notice that the light sensor directly above the plant was activated on and off. Perhaps the sensor picked up the increase in heat that the plant was emitting.

The image below shows the spathe closed after a day with the released pollen visible at the tip. The red colour is a resin released that is nutrient rich lipids for the pollinating beetles

The inflorescence is finally closed and just some fluffy pollen and a hint of resin.

Basically, the Philodendron sexual anthesis proceeds as follows:

The spathe begins to open during the female anthesis. The spadix increases the temperature through thermogenisis. The infertile male flowers emit pheromones in waves. The pollinator scarab beetles, attracted by the pheramones and the heat emitted by the spadix push their bodies down into the floral chamber where the female flowers are receptive. The beetles bring pollen on their bodies from another inflorescence to pollinate the female flowers in the floral chamber. they feed on the nutrient rich lipids and also take the opportunity of reproducing. There can be 5-10 beetles at a time.

This lasts for only one day and then the female flowers are no longer in anthesis and receptive to pollination. the spathe begins to close forcing the beetles upwards

Then the male anthesis commences and the male inflorescence produces pollen that the departing beetles take with them to another plant. The male anthesis lasts about 24 to 36 hours and the inflorescence then closes.

If pollination has occurred the fruit will form, berries that contain seeds to initiate a new generation of Philidendron hastatum.

Care of Philodendron hastatum

From the understanding of the plants native growing conditions and what we have read the following points for care are obvious:

  • Situate your pot whether indoors or out, in bright indirect light. This could be the brightest spot in your home or a south facing spot (southern hemisphere) outside in a sheltered area that is well lit but where no sunshine falls on the leaves.
  • Keep away from air conditioning and heating when situating the plant indoors.
  • Using a terracotta pot is a good choice because it breathes and helps prevent root rot in the case of overwatering
  • Use potting mix suitable for other epiphytes like orchids is suitable to provide a free draining mix Make sure the growing medium is well draining so that water drains away easily and yet keeps the plant moist.
  • Put a Moss Rod near the growing plant. Moss poles mimic the texture of moist, mossy bark and provide physical support for your plants to grow aerial roots and climb upward. (If only we had known what the plant was)
  • To mimic conditions try for a consistently moist soil but not soggy.If indoors water when the top inch of the soil is dry. Out doors keep well watered as winds and heat will dry out the plant more quickly. Choosing a good free draining ix will ensure that the plants need for hydration is met. Do not allow water to accumulate in the pot saucer
  • The ideal temperature for growing is between 18C to 26C with a humidity of about 50-80% humidity. This being said, our humble plant has survived the extreme heat of Sydney in its sheltered position amongst a host of other plants that create a humid micro climate. So I think that Silver sword is more resilient than one thinks if its basic needs are met.
  • Repot when the plant outgrows it pot and propagate from vegetative cuttings making the cutting right above the nodes.

I hope this post will encourage you to look at Philodendrons in a new light. They are popular and beautiful and if you have the time and patience they may bless you too with their beautiful inflorescences.

Two blooms, what a blessing.

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s