'Grosso' - Just Grown for Oil or is it?

In excess of 1000 tonnes of L. x intermedia (lavandin) oil is produced per year worldwide. For years, L. x intermedia 'Grosso' has been the world's most extensively grown lavender for oil production.

'Grosso' is a lavandin, in other words, a hybrid between Lavandula angustifolia and Lavandula latifolia. It has intermediate characteristics of both parents, having long peduncles (flowering stems) with multiple lateral branching. The habit of the plant is bushy and rounded with greenish- grey foliage. It is reasonably slow growing at first but by its third year forming a spherical mound of between 40-50cm both in width and height. So it is not one of the larger lavandins in cultivation but when in flower it can be over 1 m in height. A truly awesome sight in flower, 'Grosso' is a wonderful ornamental for mass planting or for effect. For us in New Zealand it is a plant that looks great from early January through to March if left to flower untouched. This is often a time when many other plants are suffering with the heat and dry yet this lavender never fails to impress. It is a good plant for tourists as often the earlier flowering Lavandula angustifolia cultivars have either been harvested for their flowers or oil.

For people in tourism or for those simply wanting an exciting new angle to an existing garden, why not look at planting some 'Grosso' just for effect. The peduncles are long and therefore popular with the florists both in New Zealand and overseas, the scent is divine. The only drawback if growing for the florists is that the stems need to be cut as soon as the first two flowers have opened along the spike. When cut at this stage, the flower spikes maintain their shape for use in the floral trade. If left any longer the individual flowers will fall off when drying or handling.

When deliberately left to flower longer and then dried, they are excellent for stripped flowers and the scent simply lasts for ages. 'Grosso' flowers can be combined with other lavandin stripped flowers as well for added bulk. The flower are easy to strip by hand or machine. If cutting later in the flowering season to dry, then place some sort of ground cover underneath to catch any falling flowers.

If planting just for effect, the flowers still look good in March, even if a little faded. Plants can then be cut back and trimmings and flowers and stems make good compost.

For those growing 'Grosso' for bulk commodity essential oil, then the market is still there but as the oil has always been readily available to the consumer at a relatively cheap price on the international market, prices in New Zealand will increasingly reflect this, particularly as there are now a number of 'Grosso' growers in New Zealand. However, there will always be a demand for this oil for value added products such as soaps, candles, disinfectants, shampoo and the like. The essential oil produced in New Zealand is of top quality and we have our soil types and extended sunlight hours to thank for this. 'Grosso' as an oil plant was always going to compete on the world scene and we have always recommended that anyone considering growing 'Grosso' as an oil crop look carefully at their market/markets before contemplating the number they wish to put in the ground. A few 'Grosso' in the ground still has its benefit as does a large number where there is a connection with a marketing company or other outlets nationally or internationally. The return for 'Grosso' essential oil will simply reflect current market prices. For other growers it may simply be time to look at alternatives for this versatile crop and in doing so, not forget the simple beauty of this plant that has a power to attract and an addictive ability to totally absorb the senses.

Oil Plants Extraordinaire

For all the years we have been growing lavenders, and for Virginia that is over 20 years, we have advocated growing Lavandula angustifolia cultivars. They are wonderful plants. Not only are they the hardiest of the lavenders but they also come in a subtle array of colours from deepest aconite violet through to purple, violet, lavender and pinks and white. Many of them smell divine and we prefer their scent to the sharper tones of the lavandins. They also make better hedges than their L. x intermedia counterparts.

Another great factor is that the essential oil produced from some of these cultivars is top quality. Two that are performing particularly well in New Zealand conditions are Lavandula angustifolia 'Pacific Blue' and Lavandula angustifolia 'Avice Hill'. Both these plants are New Zealand raised. 'Avice Hill' is protected by Plant Variety Rights/Plant Breeder's Rights and can only be sourced through contracted growers.

Each produces a completely different essential oil from the other but they are unique and proving extremely popular. Both are being used for culinary purposes as well as the obvious fragrant market which includes aromatherapy and cosmetic products. However demand is far exceeding production at the present time and it will be some time before enough oil is produced to satisfy the consumer.

Both plants produce good fresh or dried flowers. Length of stem will depend on the timing and amount of water given.

Lavandula angustifolia cultivars are generally smaller plants than L. x intermedia cultivars. However they are fast growing and reach maturity within three years. We have found that growing in weedmat seems to considerably speed the growing process of L. angustifolia cultivars. They require one good prune a year preferably about March in New Zealand. They are very hardy and will withstand quite severe frosts. However they have a lower essential oil yield than plants such as L. x intermedia cultivars. They may only produce a third to half of what 'Grosso' will produce in a season but this is dependent on a number of factors which influence essential oil production. However one can plant approximately one third more L. angustifolia cultivars than L. x intermedia cultivars in the same area. Stems and bushes may be shorter than L. x intermedia cultivars but the monetary return on the essential oil is good.

If growing lavender to produce essential oil for one's own business then it is a good idea to have both some L. x intermedia cultivars and some L. angustifolia cultivars in the ground as the oils from the different cultivars complement each other when choosing product ranges. It also allows for the enigma of individual taste, spaces out the harvest time and gives variation in case of unexpected seasonal occurrences.

Pruning to Shape

I am often asked why our bushes look so nice and round. Do they grow that way naturally? If not, how does one achieve this?

The way we prune is to take a pair of hedge cutters and start with the outer edges of the bush and cut in a circular direction either clockwise or anticlockwise until back at the starting point. Then the top of the bush is cut and curved to meet the sides.

This gives a spherical shape to the lavender and allows the plant plenty of new growth on which to flower.

Lavender plants can be pruned to other shapes as well and often if machine cut will take on the shape of the blades and may look like a square or flattened hedge or the sides may be angled for ease of harvesting.