Root Awakening: River Tamarind’s pods are edible

Plant is the River Tamarind or Petai Jawa

This plant’s fruit look like peas. Are these edible? 

Shovan Chu

The plant you have is likely the River Tamarind (Leucaena leucocephala), also known as Petai Jawa. Its young pods are eaten as a vegetable by various communities in the region.

It is seldom cultivated nowadays, as it is considered an invasive species that grows rapidly and forms dense thickets that crowd out existing plants. Its branches break easily and large trees can be uprooted during storms. 

Azalea is likely diseased

I recently found soot-like mould at the bottom part of the azalea topiary stem. The bark had become darker around that spot and the leaves started to shrivel and dry up. I cut off the diseased stem and temporarily soaked the stem in water, which seems to have revived the plant for now. How can I rescue this topiary?

Leah Ang

It sounds as though your azalea plant has a disease that was brought about by wet conditions at the base of the plant. The exact cause cannot be identified easily and may require laboratory testing to determine.

Was the plant repotted but planted too deeply? Moist potting media can let disease-causing organisms in through the bark, where they can infect the stem tissue. This can prevent a plant from taking up water from the roots, eventually killing it.

Your potting mix resembles peat and seems to contain a large amount of organic matter. Such materials hold a lot of water, and if the root zone does not dry out, the plant’s roots will suffocate and die.

The cut portion you have described may not root reliably due to the woody stem and large number of leaves, which can cause it to lose water quickly. You may want to take shorter tip cuttings and try rooting them. There are numerous online resources on propagating azalea plants from stem cuttings.

Heliconia’s flowering habit depends on cultivar, growing conditions

Our Bird of Paradise plants recently developed yellowish leaves. Given that Singapore has spells of hot, dry weather, how many times should we water the plants? Also, how do we nurture the flowers?

Justin Chia

Your plant is a cultivar of the Heliconia. This genus of plants is commonly confused with the Bird of Paradise, a relative from a different genus (Strelitzia). Different Heliconia cultivars exhibit varying flowering habits. Without the flowers, the identity of your plant cannot be ascertained.

Established plants may be able to withstand short periods of drought. However, you can reduce plant stress by applying a layer of mulch around the base of the plant to keep the roots cool and reduce the rate of water evaporation. Ensure the soil you use to grow your plant contains organic matter which can retain water.

Avoid feeding your plant solely with organic fertilisers, as these are often rich in nitrogen that prompts the plant to produce lush foliage over flowers. Instead, try using a fertiliser designed for flowering plants. 

Lastly, thin out crowded growth by cutting at the base of selected pseudostems. This will open up the clump to allow better penetration of sunlight. Crowded pseudostems tend to produce a “shaded” effect, as leaves shade one another out as the plant grows, leading to a messy appearance. 

Roots could be those of nearby plants

There seem to be some roots in the soil of my pot and planter box. I see them whenever I try to loosen the soil or empty the pot, and they come back even after being pulled away. Are these roots absorbing nutrients in the soil, and is the soil still usable? How do I salvage the soil?

Peh Yew Guan

The description is slightly unclear. Did the mass of roots come from the plant that was growing inside the empty pot or from plants in the planter box? Either way, such aggressive roots take up space in the soil and will compete with existing plants for nutrients and water. 

If you want to grow plants in the planter box, the roots need to be removed. If the plant that produced those roots is growing in the same box, it may need to be removed or transplanted to grow elsewhere. Such a task can be quite messy and laborious to undertake, so it is best to engage the services of a landscape contractor.

If the roots came from the plant growing in the empty pot, you will need to isolate it so its roots do not grow into the soil of the planter box. Place concrete or stone pavers below the pot. Also, check and move the pot regularly to dislodge the roots trying to grow into the planter box. 

Shrub is Malayan Banyan

I found this plant growing in the pot that used to house a basil plant. The basil is dead, but this plant is thriving. What is it?

Chia Siew Eng

The plant is the Malayan Banyan (Ficus microcarpa). It is still a young plant and if it is planted outdoors in the ground, it can grow into a huge tree. It will thrive in well-draining soil with exposure to full sun. Keeping it inside a small pot will constrain its growth.

Its seed was probably brought to the pot by a bird that had eaten its fruit.