Lottah Nursery Tasmania, Australia

TISSUE CULTURE OF LILACS

Traditionally lilacs have been grown from seed, suckers or by grafting superior clones on to compatible rootstocks. Lilac seedlings of several species, privet stem cuttings as well as ash seedlings/root cuttings have all been utilized as rootstocks.

In recent times there has been a move away from using rootstocks for various reasons, and nurserymen have been trying to produce cultivars on their own roots. While cuttings taken at the right time are often successful for many species, this is not always a sure recipe for the vulgaris clones.

For more than two decades some of the leading nurseries in the US and Europe have been using tissue culture for propagating lilacs on their own roots. While the main reason for resorting to micropropagation is to produce large numbers of selected clones within a short period, we have discovered it to be no less effective in producing small numbers of vulgaris cultivars which are recalcitrant to initiating roots by conventional means. The following is a short photo-essay on the process.

	The most difficult part of the operation is obtaining material free of bacterial and fungal contamination. Succulent terminal cuttings are divided into single node 'explants' and agitated in dilute chlorine for varying lengths of time to try eliminate pathogens.
	Cleaned explants are placed in nutrient agar under aseptic conditions and stored under lights at a constant fairly high temperature for several weeks.
	Explants free of contamination make 20-50 mm of growth over several weeks and are ready for weaning and rooting, or for further division to repeat the process until the required quantity is achieved. Leaves at this stage are tiny, resembling those of young seedlings than that of mature plants.
	A tray of cuttings after root initiation and several months' growth in the greenhouse, around 150 mm height.
	Our first micropropagated lilac, standing all of 125 mm after a season's growth in the greenhouse. Note the sucker emerging from the left of main stem. A second season's growth should see this on the market.
	Well grown tissue cultured S. v. 'Sensation' towards the end of the second season at leaf-fall, standing nearly 1 m high. Some cultivars such as S. x hyacinthiflora 'Maiden's Blush' branch more easily and make less height.