This blog reviews the latest products, plants and innovations in gardening. It also provides a link for my many gardening friends who are members of the GardenMessenger and Seedmessenger Yahoo groups and their sub-groups that I moderate.

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I am a semi-retired UK botanical garden curator and former international horticultural consultant, who has worked extensively in Europe, the Middle East, North America and Australia. I spend part of the year in Australia and part in Europe, mainly due to family and work commitments. I earn my living from writing and editing Internet copy, articles and books. I have written over fifty books on gardening and have been translated into twenty-four different languages. I am a former UK Garden Writer of the Year and a previous Quill & Trowel Award Winner from the Garden Writer’s Association of America. I am interested in developing gardening communities on the Internet and I manage the popular GardenMessenger Yahoo group, along with its various sub-groups like PondMessenger and SeedMessenger. I also edit International Water Gardener and its associated regional web-sites.

Thursday, April 20, 2006

Black Leg, Geraniums, the Vegetable Group and Cuttings Again

Propagating geraniums

Mary, who lives somewhere in Kentucky, asked me about propagating geraniums. Not the herbaceous ones, but those that we should really call zonal pelargoniums. The brightly coloured bedding and houseplant kinds. She always has problems with the cuttings rotting off at the base. I expect most of us at sometime have experienced this problem. Perfectly good short stem cuttings turn black, the tissue seeming to tighten and shrivel, the cutting then collapses. This is a disease called Black Leg. Nobody has isolated the precise cause as far as I know, but it is certainly a disease, acknowledged by most of the experts to be a combination of fungi with the possible intervention of a bacteria. There is no cure for the problem, although sometimes the removal of the blackened portion of the cutting when first noticed, and attempting to re-root it in fresh sterilized compost does work. Unless the cuttings are very precious and going to be difficult to replace, then they are really best discarded.

Geranium cuttings are usually short shoots 7.5-10cm (3-4ins) long that have their flower buds removed, although ideally they should be of non-flowering shoots. However, many geranium cultivars flower so freely that it is often difficult to find non-flowering cutting material. Geraniums that are very green have usually been grown "soft", that is well fed and watered and producing succulent stems. These are not ideal for cuttings and often succumb to Black Leg quite readily. It is always better to take cuttings from those that have been grown a little "harder". Often if cultivated in a soil-based compost and fed sparingly they will flower more profusely and the attractive dark zones on the leaves will be more pronounced. Such plants usually have a pinkish caste and provide perfect cutting material.

Use non-flowering material

Once the cuttings have been removed, they should be cut at a node or leaf joint. It is here that the cambium cells which will hasten the rooting process are more numerous. Remove the little leaflets at the leaf joint as well as any lower leaves that may touch the compost, as they may initiate rotting. Using a hormone rooting compound is optional, but is generally preferable as not only does it stimulate rooting, but it is usually combined with a fungicide that helps prevent decay. This is a fairly standard method of increasing geraniums and is usually achievable, even by those who have no claim to being green fingered.

In cases where there is a scarcity of plant material that is suitable for cuttings, then multiple leaf bud cuttings can be taken. These do not make plants quite as quickly, but they do enable many more cuttings to be started. If you look at the leaf joint of a geranium, you will see between the leaf and the stem a small bud. As the plant grows this turns into a shoot that ultimately is taken as a cutting. Why not remove it now, along with all the others that look good and viable? This means that a standard geranium may yield half a dozen leaf bud cuttings. Remove a piece of stem with the bud and leaf attached. It need only be a small piece of stem. Remove the leaf blade, but leave a little bit of leaf stalk so that you can handle the cutting without damaging it. Dip the raw end of the stem in rooting compound and gently place the cutting in a pot or pan of sharp sand. Keep damp, but not wet, and you will find the majority will root. Once growth starts they can be potted individually.

Join the Vegetable Group

Within GardenMessenger there are a number of specialist interest sub-groups. Albert from Greater Manchester in the UK has complained that there is nowhere for him and his friends to go in the GardenMessenger community. They are all vegetable gardeners, or allotment holders as he calls them, and it would be nice if I could start a vegetable gardening community. He promised to join and cajole his vegetable growing friends to do so as well. Having seen how successful the TomatoMessenger group has been following a little bullying from the membership, I took him at his word, and sure enough we have a quorum. So if you are interested in any aspect of vegetable growing and would like to meet fellow enthusiasts, you would be very welcome to join Albert and his friends in the GardenMessenger Vegetable Group click here.

Finally a footnote at the request of Anastasia of the RoseMessenger group. She posted a note on the RoseMessenger message board requesting that I post pictures on the blog of the difference between net-veined leaves and parallel-veined leaves following my article on rules for cuttings - so here goes.

Net-veins all radiate out in a network with secondary networks coming from the primary veins.

Although the veins are not always mathematically exactly parallel, they all run alongside one another and do not create an interconnecting network.

Happy Gardening



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Photo: Geraniums Gardening Express
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