In Production Today: Subtropical Spring

Arrowroot/ Comfrey Challenge: which plant is most productive in the subtropics?
The comfrey/ arrowroot challenge: Which is most productive in the subtropics?

Sweet spring: Do you find that when you are picking certain seasonal plants from your garden that life somehow seems sweeter? Right now, my winter sown chervil and watercress have such soft, juicy, delicate, fresh growth in my garden they are a delight to handle.

I grew up with these two crops, there always seemed plenty in my grandparents London garden. Like mint, they escaped from positions dedicated to their cultivation and their seed found its way into all the nooks where they were happy to grow themselves. All we needed to do was pick and enjoy them. Culinary bliss!

Cold damage on tropical plants is often slow to surface. I’ve spent about four days this month trimming and pruning back tender plants that were damaged by a wintry East Coast Low weather system last month.  The Mexican tree spinach (Cnidoscolus aconitifolius) entirely defoliated, and the Pandan (Pandanus amarylliifolius) has yellowed and many leaves are unuseable. Chilli fruit stopped swelling, my numerous ‘Piri Piri’ chillies are tiny, like red dots.

The cool really suited my annual nettles (Urtica urens) which made nettle soup, I’ve got one bag full of Arrowroot (Canna edulis) rhizomes waiting to be cooked. The mildly spicy chilli ‘Hungarian Hot Wax’ is great pickled, but it only lasted a fortnight before it was all eaten.

Pigeon pea (Cajanus cajan) have been late, I’ll pick them later this week.

In this garden I grow Queensland arrowroot (Canna edulis) for mulching and compost making because it grows so reliably. So many visitors have asked why I don’t grow comfrey (Symphytum x uplandicum) for compost-making and mulching. I guess the reason is because comfrey, a cool climate perennial, has been popularised by northern hemisphere gardeners who cannot grow a decent crop of Canna edulis, a warm climate perennial.

I get around 45kg of plump, shiny purple, ready to cook rhizomes from 10 square metres of soil. Rhizomes and leaves contain 10% protein and make valuable stock fodder.

I have cleared a bed where I will trial equal plantings of both. Over the spring to autumn growing season I hope to demonstrate which species – either comfrey or Queensland arrowroot – uses the least amount of water to grow successfully, and which produces the greatest amount of organic matter. I dug the bed over, working in well-rotted horse manure into the top soil. After planting, I mulched the surface with layer of sugar palm flowers (Arenga pinnata). This palm bloomed in autumn and left a pile of fallen flowers big enough to fill three wheelbarrows.

The Comfrey/ Arrowroot Challenge 2015 – 16: The trial bed is pictured, above. At the first cut (November 2015), I harvested 9.09kg arrowroot and 5.93kg comfrey; second cut 8.85kg arrowroot and 3.42kg comfrey (January 2016); third cut 6.41 kg arrowroot and 2.29kg comfrey (March 2016).

In terms of water, comfrey required eight times as much water to keep it growing. Without daily watering in dry weather it was very susceptible to wilting, unlike arrowroot which could be watered with half the volume of water every third day and still keep growing strongly.

The verdict: I harvested 23.35kg arrowroot compared to 11.64kg comfrey, that is double the green weight for one sixth of the water. Arrowroot is clearly the better in my coastal subtropical garden.

The stinking roger are tall, delicate and flowering their hearts out. Time to use it to make ocopa with huacatay sauce!

Now to finish mulching my spice border with home made compost. Here’s my spring menu:

Edible roots and shoots

Aerial potato, Dioscorea bulbifera;
Arrowroot, Canna edulis;
Cassava, Manihot esculenta;
Cassava, Manihot esculenta ‘Variegata’;
Cocoyam, Xanthosoma saggitifolia;
Sweetpotato, Ipomoea batatas ‘Ace of Spades’ (small, tasty tubers);
Sweetpotato, Ipomoea batatas ‘Marguerite’;
Yam, winged, Dioscorea alata;

Edible leaves

* Basil, lemon, Ocimum x citriodora;
* Basil, sacred, Ocimum tenuiflorum;
Cabbage, Ethiopian, Brassica carinata;
Cha-plu, Piper sarmentosum;
Chickweed, Stellaria media;
* Chicory, Cichorium intybus;
Chicory, Cichorium intybus ‘Red Dandelion’;
Chinese celery, aka smallage, Apium graveolens;
Chervil, Anthriscus cerefolium;
Chives, Allium schoenoprasum;
* Coriander, Coriandrum sativum;
Curry bush, Helichrysum italicum;
Curry leaf, Murraya koenigii;
Dandelion, Taraxacum officinale;
* Dill, Anethum graveolens;
* Endive, Cichorium endivia ‘Green Bowl’;
Eschallot, Allium cepa var. aggregatum;
Fennel, Florence, Foeniculum vulgare Azoricum Group ‘Zefa-Fino’;
Garlic chives, Allium tuberosum;
* Green Amaranth, Amaranthus viridis;
* Huauzontle, Chenopodium berlandieri;
Japanese parsley, Cryptotaenia japonica;
Kaffir lime, Citrus hystrix;
* Lagos spinach, Celosia spicata;
Landcress, Barbarea vulgaris;
Lebanese cress, Aethionema coridifolium;
Lemongrass, Cymbopogon citratus;
* Lemongrass, Native, Cymbopogon flexuosus;
* Love-lies-bleeding, Amaranthus caudatus;
Love-lies-bleeding, Amaranthus caudatus ‘Green’;
Lettuce, Lactuca sativa ‘First Fleet’;
Marjoram, Origanum marjorana;
* Mint, Corsican, Mentha requienii;
Mint, native, Mentha satureioides;
Mint, Moroccan, Mentha spicata;
Mizuna, Brassica juncea var. japonica ‘Red’;
Mizuna, Brassica juncea var. japonica ‘Ruby Streaks’;
* Mustard, Brassica juncea ‘Osaka Purple’;
* Mustard, Brassica juncea ‘Giant Red’;
* Nasturtium, Tropaeolum majus;
* Nettle, annual, Urtica urens;
Old man saltbush, Atriplex nummularia;
Onion, Tree or Egyptian Walking, Allium x proliferum;
Onion, Welsh perennial, or perennial spring onion, aka scallion, Allium fistulosum;
Pandan, Pandanus amarylliifolius;
* Parsley, Petroselenium crispum ‘Italian flat-leaved’;
* Purslane, Wild, Portulaca oleracea;
Radicchio, Cichorium intybus;
* Rocket, Wall or wild, Eruca saliva;
Society garlic, Tulbaghia violacea ‘Variegata’;
Society garlic, Tulbaghia violacea ‘Fairy Stars’;
* Stinking Roger, Tagetes minuta;
Sweetpotato, Ipomoea batatas ‘Ace of Spades’;
Sweetpotato, Ipomoea batatas ‘Marguerite’;
Thyme, Variegated, Thymus serpyllum ‘Variegata’;
Variegated four seasons herb, Plectranthus amboinicus ‘Variegatus’;
Variegated four seasons herb, Plectranthus amboinicus ‘Bayside Beauty’;
Vietnamese mint, Persicaria odorata;
Watercress, Nasturtium officinale;

Edible petals

Bedding Begonia, Begonia semperflorens;
Begonia, Begonia ‘Dragon Wings’;
* Cranberry Hibiscus, Hibiscus acetosella (excellent for tea);
Canna, Canna iridiflora;
Goldenrod, Solidago sp.;
* Stinking Roger, Tagetes minuta;

Edible seed

Chilean wine palm, Jubaea chilensis;
Fennel, Florence, Foeniculum vulgare Azoricum Group ‘Zefa-Fino’;
Pigeon pea, Cajanus cajan;

Fruit and pods

Banana (ripe), Musa x sapientum ‘Java Blue’;
Banana (green), Musa x sapientum ‘Ladyfinger’;
Banana (green), Musa x sapientum ‘Goldfinger’;
Bean, climbing, Phaseolus vulgaris ‘Purple King’;
Capsicum, Capsicum annuum ‘Bull’s Horn’;
Chilean wine palm, Jubaea chilensis (preserved in pandan-flavoured syrup);
Chilli, Capsicum annuum ‘Hungarian Hot Wax’;
* Chilli, Capsicum annuum ‘Long Red Cayenne’;
* Chilli, Capsicum annuum ‘Piri Piri’;
Kaffir lime, Citrus hystrix;
Lime, Tahitian, Citrus x latifolia;
* Mouse Melon, Melothria scabra;
* Pawpaw, Carica papaya ‘Southern Red’;
Pepino, Solanum muricatum;
Tomato, Lycopersicon esculentum ‘Apollo’;

Medicinal / Spices

Aloe vera – leaf juice used to heal sunburn, scratches, and for shampoo;
Bulbine frutescens – leaf juice used to treat burns, rashes, as an infusion for sore throats;
Brahmi herb, Bacopa monnieri – aids cognitive function;
Cardamom, Eletteria cardamomum;
Cardamom, False, Alpinia nutans;
* Catnip, Nepeta cataria; the juice left by rubbing elbows and ankles with fresh leaves helps deter mosquitoes;
Galangal, Alpinia galangal – spice used like ginger with similar properties;
Ginger, Culinary, Zingiber officinalis – spice that helps decongestion of catarrh, aids digestion, blood flow;
Ginger, Shampoo, Zingiber zerumbet – from Seed Savers. Juice from leaves and roots (rhizomes) used to wash hair;
* Greater celandine, Chelidonium majus – stem juice kills warts on hands;
Krachai (root), Boesenbergia rotunda;
Rosemary, dwarf, Rosmarinus officinalis ‘Benenden Blue’;
Rosemary, fastigiate, Rosmarinus officinalis ‘Miss Jessopp’;
* Skullcap, Blue, Scutellaria lateriflora;
Turmeric, Curcuma longa – spice with anti-cancer, anti-stress properties;

* denotes a volunteer crop

Total 104 taxa

Jerry Coleby-Williams
24th August 2015 


5 Comments Add yours

  1. Chris says:

    I always like to read what you are planting next . I am harvesting great lettuce , spinage , radishes and soon peas. Will sow Cucumbers today, before the rain arrives I hope.
    I have about 15 Persimmon seeds sprouting from our ex garden and one is already 2 feet high a lovely shaped tree but non have lost their leaves as yet. Hmm except 2 about 6″ tall ones.
    I grew the original 2 Persimmon trees from seed in Sydney 20years ago , all bore beautiful fruit.
    Had to leave them behind when we moved a few month ago, but I collected seeds and now have these young tiny trees .
    Kind regards,


  2. Richard Moran says:

    Dear Jerry

    I read your excellent advice on wetting agents and became concerned because I have used bags of what is described as a premium native plant growing mix for pots and garden beds and the mix includes a wetting agent. It had the word organic on the package but of course that only referred to some of ingredients

    In the past I have mainly used a compost derived chiefly from the leaf drop of an old liquid amber tree but was running short and bought the mix. I think I bought four 25 litre bags.

    I have used the mix as follows:

    * To fill a hole where I removed soil after a tradesman spilt what he said was paint and the soil smelt strongly of mineral turps. For the bottom of the hole I used natural clay from the cats kitty litter and put the native plant mix on top.

    * To fill some shallow holes in lawn under the old grey gum after damage when tiles were delivered for new roof. Top soil would have been better but the bags were there and I thought being for native plants it would suit the old grey gum

    * To mix with the very heavy clay soil that seems to be the dominate soil in the new place I have recently purchased. I have mixed in the bagged soil when planting the area with indigenous plants from the local council nursery. I have also used an organic tea tree product which is a by-product of making tea tree oil to mix in with the heavy clay.

    At this point the mix is well and truly integrated with the existing soil so I would have to accept that any damage is already done, however, I would welcome any comment or advice.

    I appreciate you can’t respond to everyone so will understand if you are unable to do so

    Best regards

    Richard Moran

    Caringbah NSW 2229

    1. Dear Richard, Now you know better, stick to traditional organic methods for improving clay soil – as also detailed on this website. Regards, Jerry

  3. Cara Ryan says:

    What were the results of your experiment jerry ? 🙂

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