23 August 2011

Waterwise indigenous gardening on the sandy flats

Alice Notten, Chief Interpretive Officer at Kirstenbosch National Botanical Garden, gave an entertaining and informative talk on Waterwise indigenous gardening on the sandy flats. The talk was hosted by the Friends of Meadowridge Common, and took place in the Meadowridge Library - one of several interesting talks hosted by the Friends over the years. Alice Notten is a botanist and horticulturist who has worked at Kirstenbosch for many years, and is known by many for her interesting articles on gardening with indigenous plants on the website PlantZafrica as well as those in Veld & Flora. This is a summary of her talk, with links to the PlantZafrica site, where you can obtain more information on gardening with specific plant mentioned.
When Alice bought a house in Plumstead, she was a bit shocked at the windy, sandy conditions she faced as she had only had experience gardening in the rich, loamy soils of Johannesburg, and then the rich loamy soils of Kirstenbosch where she had lived up to this point. Anyone who has gardened in this area knows the type of soil that she was confronted with: sandy, oily soil that repels water. Alice started off by planting a windbreak around the perimeter, finding Searsia (Rhus) pendulina to be the most successful fast-growing, bushy hedge,
as well as the pioneer Keruboom (Virgilia divaricata and V. oroboides). This is an excellent pioneer tree that will act as a "nursery species" by providing protection for slower growing, more sensitive plants that you can plant around it. Being a pioneer species, the Keurboom will die in about ten to fifteen years by which time the slower growing species will be well established.
Another good hedge plant is Tecoma capensis. It is hardy and colourful and fast growing.

Searsia (Rhus) crenata also makes a good border hedge. The Krantz Aloe (Aloe arborescens) is an excellent choice for a colourful, waterwise hedge plant that will attract sunbirds.
Then to get a few trees up and shading the garden, your first choice should be this underrated small tree, the Coastal Camphor Bush (Tarchonanthus littoralis). Be sure to get a female plant as the males do not produce this froth of white that lasts for months on the tree.
Turning her attention to the windswept central beds, Alice advises that you plant a few hardy plants like the Common Agapanthus (Agapanthus praecox) that will provide a windbreak and mulch trap so that other plants can be established around it.
The Rose-scented Pelargonium (Pelargonium capitatum) will very quickly take over, but if you deprive it of water, it is not as rampant as it can be and will provide colour and a trap the mulch and topsoil that would otherwise blow away in the strong Southeaster. It has the added advantage of being very easy to grow from cuttings for those of us for cannot afford to visit garden centres too often!
The Smelly Plectranthus (Plectranthus neochilus) likewise is easy to grow from cuttings and will provide colour in places where other plants do not thrive.
Interplanted with Helichrysum petiolare it looks pretty good!
Another hardy plant that can take over, but can be controlled by not watering too often, is the Bush Violet (Barleria obtusa).
For a groundcover, especially in a paved area, try various gazanias and other daisies. One that Alice found particularly hardy, is the little known Senecio crassulaefolius, which has rather interesting little flowers and is indigenous to the Cape Peninsula, growing in rocky crevices.
Another plant that is easy to grow from cuttings is the Plakkie or Pigs Eat (Cotyledon orbiculata) which Alice found rather disappointing in her garden but which seems to thrive in other sandy soil gardens nearby.
The attractive leaves of the Plakkie make it a popular and spectacular potplant.
The March Lilies (Amaryllis belladonna) that come up in the early autumn, even evinced a response from the non-botanically minded neighbours who remarked on this spectacular flower.
Alice then set about trying to grow plants that would have occurred on these sandy flats before houses were built. Having identified the vegetation type as Sand Plain Fynbos, which is known for its acidic soils, Alice obtained a few examples at the Kirstenbosch Plant Sales, and found that this pretty Phylica ericoides did well in her garden. As with many plants, a good time to plant is in early autumn so that they have time to "settle" before the harsh, dry summer sets in.
Another locally indigenous plant, the Orange Hermannia (Hermannia pinnata), also does well in sandy, dry gardens as an edging plant, a groundcover or in a rockery or hanging basket.
Another rewarding, colourful addition to the garden was Felicia fillifolia.
Protea scolymocephala also did extremely well in Alice's garden.
Another member of the protea family that did well in the waterwise garden was the Line-leafed conebush (Leucadendron linifolium).
Podalyria sericea, the Silver Sweet-pea Bush, was also disappointing and failed to thrive in Alice's garden, although it does well in other sandy gardens on the Cape flats. Alice wondered why, and discussed the fact that several acid-loving, Sand Plains Fynbos plants just hated growing in the Plumstead garden which falls fair and square into . Ernst van Jaarsveld pointed out that in his opinion, many older gardens, even if they start out acidic, soon become alkaline after years of adding fertiliser and leaching of the soil. Also, there was a large Eucalyptus (gum) on the pavement outside the house which also makes soils more alkaline. Plant more alkaline-tolerant plants and see, was his advice.
So Alice planted the Bredasdorp Protea (Protea obtusifolia) which occurs on the limestone soils of the Agulhas Plain, and it did extremely well, outstripping the existing Common Sugarbush (Protea repens) in no time.
The thing about acid-loving plants is that they can only tolerate acidic soils and will die if planted in alkaline soils, but alkaline-loving plants will also thrive in acidic soils, so you can't really go wrong by planting alkaline-loving plants, Alice said. She urged members of the audience to get their soil tested and said that testing kits were readily available at plant centres these days.
The aniseed-scented Bergboegoe (Agathosma ciliaris), a locally indigenous buchu of the coastal flats, seemed to like the slighly more alkaline soils of Alice's garden, and provided it is looked after to begin with, is waterwise and hardy.
Another lime-loving member of the protea family is the Albertinia Pincusion (Leucospermum muirii) and it did well in Alice's garden.

There was quite a long discussion on the topic of "to mulch or not to mulch" as Tony Rebelo's letter to Veld & Flora stating that fynbos does not like mulch and the oily soils are perfectly good at keeping in the moisture underneath the plants had been noted by many in the audience. Alice basically agreed with Tony but in an artificial environment where soils have largely been leached and transformed, a little mulch is desirable, but she warned against using well decomposed damp compost. So, once you understand your soil, it is possible to find lots of beautiful, interesting and unusual plants to fill your garden. Visit Kirstenbosch to get an idea of what the plants look like in the garden and start planning ...

Some final thoughts:
 If in doubt, test the pH of your soil. Remember that human interference can change the pH. It is easier to make it alkaline than acidic.
 Draw up a plan of your garden.
 Find out how wet your garden gets in winter, where the dry spots, or wet spots are, where does the wind come from, where is the sun etc.
 Remember that buildings, walls, paving can alter the drainage, increase flow of water after rain, and interrupt airflow, and make things hotter, drier or windier.
 Make lists of plants that used to grow in the area, and of other potentially suitable plants, short list the ones you like the look of.
Compost and mulch.
 Plant a windbreak.
 Plant nursemaid shrubs and perennials to protect the less tough.

Thank you Alice for the most entertaining and enlightening talk!