"Plant resilience"

Plants can be tough!
Sunday, 02 February 2020     

Agapanthus praecox subspecies orientalis in my driveway

In the midst of this truly awful summer, there are very few things that provide much cheer; however, the resilience of some of our plants in the face of the extreme heat and drought is quite astounding. It's certainly the case that I have lost quite a few plants this summer, but many others are proving to be tough customers. I plan to replant much of my garden this coming winter in order to utilise more of these stalwart specimens.

Whilst determining which plants are going to be keepers in this era of longer, hotter, drier summers is going to be a matter of trial and error, along with close observation, I am interested in looking for patterns and themes in the most stoic of the survivors. One obvious approach is to look at the provenance of plants. My main casualties this summer have been the remaining cool-climate specimens that I still loved to grow from my cottage garden days, when I thought any plant could grow anywhere, if I wanted it to. Bitter experience has taught me that, funnily enough, plants that hail from snow-capped mountains in Europe or the Himalayas don't do that well in hot old Sydney. My garden now chiefly contains plants that come from warm temperate or subtropical regions of the world! Those from South Africa, South America (but generally not the mountainous areas), Mexico, some parts of Asia, southern China - and, of course, plants native to the Sydney region - on the whole do very well. Mediterranean plants are a bit hit and miss, as many dislike our summer humidity, but as our summers are getting hotter and drier, they are likely to do better than when we had a lot of summer rain.

There are a number of plant characteristics that are associated with heat and drought survival. Leaf types are often a good indicator. Silver or grey foliage reflects light from leaves, resulting in less water loss from transpiration. In many cases, these leaves have an interesting texture from other features to reduce transpiration: such as a protective layer of down or hairs to trap moisture and reduce the effects of wind (giving a velvety look) or a surface wax (which gives a polished finish). Silvery-leaved plants that have done well for me include Artemisia 'Powis Castle', Salvia discolour, Lychnis coronaria, Helychrysum petiolare and Plectranthus argenatatus (the last two plants do well in shaded areas).

Having small leaves is another plant adaptation to drought and heat, as this gives less surface area on foliage and hence reduces water loss from transpiration. I have definitely noticed that my small-leaved Salvia specimens, such as Salvia microphylla cultivars and hybrids, Salvia muirii, Salvia 'Marine Blue' and Salvia semiatrata are surviving very well. The larger-leaved Salvia are going OK, but are wilting more on hot days. Other plants with compact foliage include many types of daisies (Erigeron, Argyranthemum (Marguerite daisies), Aster and Tagetes), Linaria purpurea, Gaura, Verbena and grassy-leaved plants in general (such as Miscanthus, Poa and Lomandra).

Aromatic leaves are said to contain scented volatile compounds that appear to increase the air density around them and cool foliage as they evaporate. I certainly have noticed that a number of my summer survivors have aromatic leaves: rosemary, Nepeta, Salvia fruticosa, scent-leaf Pelargonium and oregano, though they often also have some of other leaf features already mentioned as helping plants to cope with drought and intense heat.

Succulent plants are an obvious choice for drought and heat tolerance, as their stems, leaves and sometimes their roots have the ability to store moisture to help survival. Some of my favourite genera include Kalanchoe, Crassula, Schlumbergera (zygocactus) and Sedum. These need to be planted in a spot with good drainage (or in pots), as heavy rains that occur in storms can lead them to rot if the water cannot get away. Semi-succulent plants include the wonderful array of Begonia, ranging from groundcovers to hefty shrubs, and the various forms of Pelargonium. All have endured this summer very well!

Particular adaptations of roots can also signify plants that cope well with heat and lack of rain. Thick, fleshy roots or rhizomes are a feature of some of the good doers in my garden over summer: Agapanthus (though their leaves were scorched on the 47-degree day in January!), Clivia, Alpinia, and Chlorophytum. Some fleshy-rooted plants become dormant in the heat: Acanthus and Alstroemeria hybrids - these will reappear later in the year. Of course, bulbous plants are also well adapted to drought, being dormant during summer. The pretty rain lilies (Zephyranthes species and cultivars) flower whenever rain does fall over summer despite being leafless most of this season due to lack of water! The gorgeous belladonna lilies (Amaryllis belladonna) from South Africa are just starting to send up their trumpet flowers now, unscathed by the summer heat. South African spring bulbs survive very well in our climate, and include Freesia, Babiana, Ixia and Sparaxis.

One mechanism that plants can use to cope with heat and drought is to slow their growth: I have noticed this happening with many of my plants. After the rain two weeks ago, they perked up very quickly and began growing again. The heatwave this weekend has slowed them down again; I live in hope of further rain this coming week! In the meantime, I salute those plants in my garden that have managed to live through these dreadful times, and plan to spread them through my garden.

 Reader Comments

1/10  Margaret - 2122 (Zone:10 - Warm Temperate) Monday, 03 February 2020

Thank you for sharing your observations about plants which appear to cope with the extreme heat we have suffered this summer. I concur with them. Some plants which I would have expected to be more robust have not, others have flourished. In my garden, gerbera, coleus, penstemon, assorted bulbs, lilium, begonia canes and rhizomes, to name a few, have been stalwarts. I am thinking about the plants in my garden, but don"t have any plans, currently, to change many, if any, except, perhaps, fuchsias. Thanks, Margaret. It is good to know there are so many stalwarts. Fuchsias have suffered in my garden and I have lost a couple this summer. Deirdre

2/10  Shaun - 2075 (Zone:10 - Warm Temperate) Monday, 03 February 2020

Thank you Deirdre on the job again! I do hope you had an enjoyable holiday and ready to enjoy nature in your garden with ongoing challenging heat! I"ve transformed my back yard into native over 9 years. My Buckinghamia (IvoryCurl) and Summer Reds have had astonishing blooms this year, in fact bee and Rainbow Lorikeet Heaven and !mine too! Shaun Those trees are gorgeous, aren"t they. I have been admiring a Buckinghamia in a nearby street - so lovely! Deirdre

3/10  Jim - 2076 (Zone:10 - Warm Temperate) Monday, 03 February 2020

Great blog thanks Deidre. One to add as a standout performer in hot/dry Sydney is Euphorbia hypericifolia "Stardust". We have it in a very hot position in and around an Acer which provides a little shade to some but most are in full sun.Impatiens are directly underneath the Acer in full shade and the combination is very attractive and hardy. I agree with you it is a marvellous plant. It seems indestructible! I am planning to split mine up and put it in more places. Deirdre

4/10  Bren - 2540 (Zone:10 - Warm Temperate) Monday, 03 February 2020

Bromeliads! They don"t need much water, and even then it is easy to provide water by filling the centres with water. Some people think the centres always must have water, but this is not correct, and may lead to the plants rotting. They do mostly like shade though, but the ones with jagged edges to the leaves usually can handle more sun. All mine are planted directly in the ground, or in hollows in trees and they all have survived the summer heat. They are certainly wonderfully resilient plants especially for shaded spots. So much variety in the colours and leaf patterns. Deirdre

5/10  Valerie - 2121 (Zone:10 - Warm Temperate) Monday, 03 February 2020

This summer has surely sorted out the survivors from those needing to be quietly retired in our garden. In the most exposed area Diosma and African Daisies/Osteospermum carried right on, whereas plants I thought might have done better are looking very sad e.g. some Salvia and a few Westringia. Even a couple of prostrate Rosemary gave up. I think the hot ground plus reflected heat were just too much. Still it has rained at last and may it continue. Thank you Deirdre for keeping our spirits up. The reflected heat may well have been a factor. Let us hope this predicted rain eventuates, everywhere! Deirdre

6/10  Christine - 2429 (Zone:10 - Warm Temperate) Monday, 03 February 2020

Thankyou Deidre, and other commenters. Much sensible food for thought there and I will add many of them to my notebook with lists for my next soon to be garden. Not much room for wilting hard to please prima donnas....well, ...maybe a few favourites...lol Yes it is hard to let go of those special ones, isn"t it! I still have a few that I can"t part with. Deirdre

7/10  Roger - 2121 (Zone:10 - Warm Temperate) Monday, 03 February 2020

Thank you Deirdre for your blog, a lot of food for thought after the horrible summer we"ve had. I"ve been surprised to find azaleas - not my favourite, but planted by previous owners - have survived fairly well with essentially zero watering by virtue of being in the shade. Same for camellias. Abelia x grandiflora, the big old-fashioned kind, has been a stalwart for me, attracting numerous honeybees and native bees for months, as it always does. Those old established shrubs are so tough. I have a few azaleas at the top of my drive that I have never watered. They haven"t wilted at all. I agree with you that having some shade in the garden is a huge help for our plants in these hot summers. Deirdre

8/10  Kristine - 2120 (Zone:10 - Warm Temperate) Tuesday, 04 February 2020

My Camellias have been burnt this summer,along with the poor tree ferns, hydrangeas.This Year my Crepe Myrtle has not flowered which is strange.The old geraniums are standing up to the heat. But the Cookatoos come every day and do some damage like breaking off my dahlias and my cane Orchids. They just break them off and drop them they are so destructive, they even pull the rain gauge of the pool fence.This summer has been the summer of all summers. it is enough to make you give up. Oh dear, it all sounds rather disheartening. I hope that the approaching rain will make us all feel much better very soon! Deirdre

9/10  Sue - 2074 (Zone:10 - Warm Temperate) Tuesday, 04 February 2020

Thanks for the blog -so glad to see a bit of rain. Many you have named have done ok in my patch as well. Also an old variety of Turf Lilly has survived and is even beginning to flower. Catharanthus roseus has flowered non-stop through the heat despite drooping a bit - is in part shade. I found Lilliums held up, even though the flowers got burnt on one 40+ day. Ceratostigma growing in the hottest spot never faltered. For some plants it was clear that part /dappled shade was a help. It is so true that shade provides so much shelter for plants so they don"t bear the full brunt of that burning sun. Catharanthus are great - so many colours and they last so long. Deirdre

10/10  Janna - UK Saturday, 08 February 2020

Really interesting to hear which plants have survived best. I"m carrying out a similar experiment at the moment, although along the lines of "which will get nibbled by deer and which won"t"! I will then do as you are and plant many more of the most robust species. Hope you can find a good list! It is currently pouring with rain here! It is a huge relief. We just hope it falls everywhere. Deirdre

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