 GROWING CLIVIA Basic requirements: SHADE GOOD DRAINAGE FROST FREE Clivia are hardy, low maintenance, shade-loving plants. They don’t like wet feet and need to be well-drained (don’t dig holes in clay soils), may tolerate a little early morning sun, but prefer full shade, and are frost tender. Prepare your soil by digging in lots of vegetative compost and/or organic fertiliser. Feed occasionally with a granular, slow release fertiliser or something like sheep pellets. Water sparingly. Clivia grow well in pots. We use a well-composted coarse bark as a growing medium (see article “In Search Of The Perfect Growing Medium” below) but other growers mix sand, perlite or pumice into the mix in varying proportions. The key is for the mix to be consistent and the pots well-drained. Pots will quickly dry out and the plants will soon exhaust nutrients, so clivia in pots need to be watered regularly (once or twice a week in summer) and need to be fed with a slow release fertilizer like Osmocote and/or liquid fertilisers. There are 6 species, and many interspecific varieties, of which C miniata with its huge flower head is most widely known. Other species have less showy, pendulous flowers but may provide colour at other times of year. C Miniata flower in Spring, C nobilis & caulescens in Spring/early Summer, C gardenii & robusta in Autumn and C mirabilis in early Summer, Interspecific varieties flower tend to flower in mid-Winter and sometimes again in mid-Summer, and sporadically in between. ARTICLE IN SEARCH OF THE PERFECT GROWING MEDIUM Since arriving in New Zealand seven years ago I have been searching for the ideal medium for growing clivia, one in which the plants thrive but the weeds don’t. I’ve tried different commercial potting mixes, mixed them with coarse barks and pumice, but somehow the liverwort, mosses and ferns seem to thrive and the clivia don’t. But I’m getting there. One of the problems with pumice in the mix is that it tends to be crushed rather than sifted whole stone. The crushed pumice is inclined to disintegrate and powder over time, and I’m not sure that this is beneficial to the mix. Some years back in my South African life I attended a talk given by Prof. Mark Laing, Professor of plant pathology at University of Natal, Pietermaritzburg. I quote some of the interesting things he had to say as contained in the booklet ‘Hints on Growing Clivia' put out by the Northern Clivia Club: "If you mix media with different particle sizes, the result is called a matrix. What happens is that the small particles fill the pore spaces of the big particles, making a dense mixture. This is the secret of concrete: sand particles fill the spaces between gravel chunks, and the cement then binds them in place. Drainage from pure sand or pure gravel is high. But if they are mixed in the right ratio, drainage is reduced to very little. So the principle is that when we mix particle sizes of a growing medium. we reduce oxygen content and drainage, and increase water-holding capacity. So if you add, say, sand to a bark medium, we make it heavier, with less oxygen and it drains LESS well." My gut feeling is that crushed pumice tends to contribute to a concrete like mix. Anyone planted their plants in concrete lately? What happens is that the water erodes passageways through the mix or down the insides of the pots through which the water runs away without really wetting the medium. In my 15 years of growing clivia some of the best grown plants that I have seen are those of Brian Tarr, Curator of the Pietermaritzburg Botanic Gardens. Brian uses 100% well-composted bark (South African Pine) which he then sieves to remove the fines so that nothing can clog up the medium. His plants thrive and it takes years for the medium to break down. This is what Prof. Laing had to say about pine bark: "In the composting process the bark is degraded to a lignin core, the biodegradable cellulose and hemicellulose being decomposed by bacteria and fungi. The result is a black, odourless medium with excellent physical and chemical properties, namely, physically stable, no toxins, good drainage and oxygen content, and good cation exchange capacity (how much fertilizer the medium absorbs and then releases to the plant). It is also completely free of plant diseases and nematodes......Mature clivia prefer a coarse medium." A few years ago I complained to my suppliers about the quality of the growing media here in New Zealand. They suggested that I try a product they call “CAN mini-chip” which is a coarse, composted (12-14mm) bark very similar to that used by Brian Tarr. I tried two mixes for a year experimentally, the one mixed 50:50 with pumice and the other100% Mini-chip. The latter produced the best results and over the past year I have switched entirely to using the product and feel it meets Prof. Laing’s specifications. This is not to say that readers should all switch to this medium, but I thought that the principles outlined would be of interest. If what you are doing works for you – STICK WITH IT. Alick McLeman We are not a garden centre but welcome visitors. Plants can be purchased direct from our nursery. Just phone first to ensure that we will be in attendance. Otherwise we post plants bare-rooted by standard parcel post to any destination in New Zealand. There is a small charge for postage and packaging.
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