GARDENING
IN ROCK
One flank of Singhoria hill slants down steeply till it hits the road where it has been levelled and given a tartop, then continues on through our Visitors Centre till it runs out of slope at a small Hanuman temple a short way below.
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Except for a small capping of sandstone at the very top, the entire hill is made of rhyolite and provides the Visitors Centre with a hard, rocky floor and barely any space to plant in.
We had laid rippled sandstone slabs on top of part of this floor (remember?)
On one side of the walkway, our Khandwalias chiseled out a foot or so of rock to create small hollows to plant in. The only deep pockets of soil were inside the planters we’d built into the blocky rhyolite wall that separated us from the road.
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We had been planting in rocky places inside Rao Jodha Park since 2006 so had learnt a thing or two about how certain kinds of desert plants – called 'chasmophytes' – make themselves perfectly at home growing inside thin cracks.
The soil that occupies these cracks arrives on the wind, which necessarily means it is made up of very fine – predominantly clayey –particles. Deep inside a crack – the thinner and deeper, the better – its soil is sheltered from the sun and dry air, which is why chasmophytes often look unstressed, even happy, in harsh desert habitats.
Some grasses do very well in rocky places.
Dr. MM Bhandari’s seminal book Flora of the Indian Desert lists something like 60 kinds of grasses that are adapted to living in rocky habitats and we knew we could plant several of them in our Visitors Centre, especially those with rhizomes that spread horizontally.
Two of the species we used with unexpected success were daab (Desmostachya bipinnata) and gharnia (Chloris barbata), which was a little surprising because both of these grasses are known more usually to inhabit moist sites.
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Our earlier discovery of rockgrass (Oropetium thomaeum) proved to be particularly useful.
This is a short kind of grass that partners with (moss-like) liverworts to anchor soil on top of rocky ledges. It is a crucial process in arid places that enables bare rocks to be colonised by plants, gradually building up a soil layer until there is enough of a substrate for bigger and more varied plants to grow in.
Without Oropetium, we surmised that all rocks in the desert would remain completely naked. We had learnt that using rockgrass – by lifting it up along with the layer of soil it holds onto below – is an extremely effective way of creating new niches and substrates for plants to grow in.
Several years after we first planted up our Visitors Centre, we learnt that these clods of what look like just a grass and some liverworts are actually made up of communities of tiny organisms that play an important role, especially in arid ecosystems. For a start, they are a lot more diverse than we had thought, with cyanobacteria, lichens, fungi and mosses in there too.
Scientists call them 'biological soil crusts' or 'microbial mats' and they are recognized to play a crucial role in stabilising desert soils, altering soil pH, and perhaps most importantly, in delaying the evaporation of soil moisture.
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Most plants that live in very dry habitats tend to be short-lived ‘ephemerals’, germinating with the first rains, then rushing through their lives in fast forward to take full advantage of just that small window of time when there is moisture in the ground.
So there is a great feast of annuals in the desert from August through November, which is when they begin to check out, leaving behind hard-coated seeds that may lie dormant for many months, waiting until the rains return the following year.
Inside the big spaces of the Park we don’t interfere with this seasonal rhythm of dying and seed-dropping. Dead plant matter goes back into the soil and the seeds remain in place, waiting patiently.
In our small ‘gardened’ space, we needed to teach ourselves not to pull out annuals when they begin to curl and dry out. We learnt that there can be something pleasing if not downright attractive about some plants in the way they look when they turn golden, along with the fraying remains of their fruiting structures. This is particularly true of several kinds of desert grasses.
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Chloris virgata early in its drying state
Q: How d’you make a garden in an intensely rocky desert site that has very little soil?
A: Er, very slowly. By trial
and error, learning and making corrections all the time.
The most useful lesson we learnt while planting up Rao Jodha Park was the role played by tiny fungal associates of plant roots called 'mycorrhizae'.
My own 'discovery' of mycorrhizae happened through a chance encounter in 2012 in a railway compartment with Dr. Ajit Varma who had found a species of mycorrhiza in the Thar desert that he was trying to patent. He told me about the importance of networks of thin fungal threads called 'mycelia' that partner with the roots of plants.
This is how it works: through photosynthesis, plants harvest carbon from the atmosphere to create sugars and lipids. Mycorrhizae gain access to these energy-rich compounds by growing in close association with the roots of plants.
What is still missing from the mix are water and mineral nutrients that lie locked up in the ground. This is where mycorrhizae step in because they are a lot more adept than plant roots at foraging for minerals in the micropores and electrically charged cavities of soil. By partnering with fungal mycelia, plants gain huge advantages in unlocking minerals that would otherwise not be ‘bio-available’ to them.
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This is true not just in the desert, but everywhere!
It's only in the last 25 years or so that scientists have become aware of how important this chemical exchange between plants and their mycorrhizal associates are.
Every year, we uncover more intricate and often astonishing details of these networks that are playfully called the ‘Wood Wide Web’. It is estimated that not just forest trees but 90% of all plant species depend on partnerships with mycorrhizae. Because the desert can be such a difficult place for plants to find nutrients in, it helps even more that they have fungal partners who can access minerals locked up in rocks.
Agaricus mycelium.
Courtesy Rob Hille, Wikipedia Commons
We didn’t always know what to do.
But it’s one thing to learn conceptually about the importance of mycorrhizae, quite another to give practical application to this knowledge.
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We bought dessicated propagules of
Dr. Varma’s mycorrhizae and placed them inside propagation sleeves in our nursery.
But we also learnt that mycorrhizae are just as diverse – maybe even more so – than plants and that depending on just one species to partner all our plants was probably a mistake.
As often as we could when we were collecting plants or seeds, we scraped together soil that we hoped would contain mycorrhizal hyphae. We experimented and changed our minds as often as plants showed us they were not happy with where we had placed them.
This was one of the most challenging and enjoyable parts of designing a natural landscape — responding creatively to cues and results and learning about what different plants 'liked'.
Some plants do brilliantly at first, then shy away when they sense competition. These tend to be ‘pioneers’, happy to be the first to arrive on a bare, rocky site, but quick to depart when others follow. Some plants are picky and show a clear preference for growing with particular associates and not with others...
Our garden in the Visitors Centre is a little different from the rest of the Park. It’s small, so we can pay it much more attention. It’s a lot easier to experiment and watch for results in a small space.
In the end, we’ve ended up with a garden of desert plants that doesn’t stay still because it keeps evolving.
I can hardly dare to imagine what it will look like in years to come.
Garden Done!
What's Next?