Sweet broom

I've gone a bit nerdy over Carmichaelia odorata, my plant of the week. My usual approach to writing about plants is to spill out all I know from my own experience, then check with the experts to see that I'm telling it the way it should be. Readers of gardening articles like, I believe, to share the feelings of enthusiasm that writers have for particular plants and know that if they need to check the science, they can open a book or go online to find the Latin names for or the taxa to which the plant under investigation, belongs. Sweet broom, Carmichaelia odorata, has required of me a little research in order that I can be sure of myself when sharing my enthusiasm for the pretty little legume that grows throughout my garden. The reason for my reliance on the plant-science community in this instance, is the broom family and it's convoluted ways. There are so many of them and describing them casually makes them all sound much the same and given that Scotch broom is one of New Zealands most disliked 'pest plants' I want to be sure that my much-cherished broom isn't dismissed as worthless when it is in fact, a wee beauty and deserving of a place in every garden. Carmichaelia odorata is native to New Zealand, as are all of the Carmichaelia family, save one that's somehow made its way from here to Lord Howe Island. We'll forgive that renegade its abandoning of our fair isles and the others in its family and want it to know that it's always welcome here,in the land of its birth. Those in the family that stayed put; all 23 of them, including little, sweet smelling odorata, do us all proud with their graceful weeping forms and modest behaviours. None are a threat to our farmers, as Scotch broom is reputed to be, and all are valued for their rarity, again, in contrast to the wanton Scot. A couple of decades ago, when I was first establishing what is now my forest garden here in Riverton, the newly-purchased property was covered thickly with the 'wrong sort' of broom and I became quite intimately associated with the yellow flowered thing and its dense growing habits. Having hand-sawed several hundred of them and seen how rapidly the seeds that fall from it every year, sprout and grow, I can understand the fear that farmers feel for it. If only with Carmichaelia odorata was so vigorous. I'd be happy to have it threaten my garden with overthrow, but that hasn't happened and I've had to sow and grow them myself. In part, that's because sweet broom favours dry and sunny sites, and mine's a well-watered garden with plenty of dappled shade but sweet broom's not an invader in any case and spreads only with help from the gardener. As with all members of the Fabaceae family, my Carmichaelia produced pods and the seed inside of those is the prefered method of propagation. Collected when dry and sown onto seed raising mix and left out of doors, watered regularly and checked for progress, they'll produce plenty of replacements for any mature bush that might be exhausted by time. It's also a simple process to grow sweet broom from hardwood cuttings, taken in the winter and poked into an outdoor cuttings bed until roots form. The suitable segements form the shape of a fan and look quite distinctive amongst the other scions in the cuttings bed so are easy to identify. Seedlings emerging from the seed trays have the distinctive 'legume' look and remind me of others in the wider family, like clover, pea, laburnum or kowhai, with the trifoliate, three-leaved form. When the established sweet broom plant flowers, it again reminds the viewer of other legumes, having a flower form similar to those afore-mentioned cousins; “pea-shaped” I read in the catalogues, though I believe that should be, “pea-flower-shaped”. If, like me, you have a garden that is not akin to the gravelly river bed favoured by Carmichaelia odorata, and you would very much like to give it the best possible environment in which to grow, you could buy in some gravel and lay it down in your sunniest spot, leaving it raised to ensure the best possible drainage. Mine are doing very well, I have to say, in loamy Southland soil and I won't go to the extra trouble of recreating their prefered conditions, though if they were languishing, I might. They're attractive shrubs, growing a couple of metres in height and creating a filmy look beside other chunkier trees and shrubs. Their flowers are delicate and scented. I looked to the literature here to be sure of an accurate description of their colour, being one of the 23% of males who suffer some form of colour-blindness and discovered a snippet of description that said, amongst a mass of measurements and obscure botanical teminology, the calyx is campanulate, its outer surface glabrous, lobes long, triangular, green and usually flushed red, appressed to corolla, the apex subcutate to obtuse, which I found fascinating, if a little opaque. The description went on to cover the petals, I think, with “broad-ovate, patent, positioning toward front of keel, apex emarginate, margins flattened...” and so on. At that point, I resigned myself to being a poor descriptor of flowers and decided that anyone wanting to see some could visit their local botanical gardens and have a squizz. In any case, they are very pretty and people with a good sense of smell say that they are fragrant in a very satisfying way. Of all of the native brooms, carmichaelia odorata is the easiest to grow and keep. Others are difficult to locate, for starters and are only found in the special gardens of rare-plant collectors, where they generally attract little attention, lacking the appeal of the fine-leaved odorata; sadly, many of our native brooms have forms that don't appeal to the ordinary gardener and so are not supported by nurseries and found often on the shelves of garden centres. The flattened stems of the Carmichaelias look as though their leaves have dropped off, and plant buyers might think the plant is in poor health, but that nakedness is due to the tough environments the members of the family often occupy, where too many leaves would be a disadvantage when water is short. Carmichaelia odorata generally holds its tiny leaves well, although parts of the plant will exhibit the stripped-down look. This doesn't detract from the appeal of the variety at all and infact, becomes a talking point for visitors to the garden.