The Lavender Grosso hedge (Lavandula x intermedia ‘Grosso’) is later flowering than many varieties, coming into its best from July onwards, when planted with angustifolia types (‘English’ Lavenders such as ‘Hidcote and ‘Munstead’) and French Lavender – a flowering season from late Spring until early Autumn can be achieved.
Lavender Grosso has neat grey green foliage that looks good for most of the year, the slender yet strong flower spikes almost seem to erupt en masse from the leaves, bearing highly scented blue-purple flowers on long wiry stems. These often continue in succession until well into Autumn.
Grosso is one of the tougher Lavenders and is the Lavender plant of choice on many commercial landscaping projects, they will not only survive but also thrive with little aftercare and are more forgiving than many other varieties if conditions aren’t quite ideal. This is also the most commonly planted variety for commercial lavender oil and flower production, it is an easy variety to harvest with mechanisation as the flowers are presented conveniently, well above the foliage.
A Lavender Grosso hedge is slightly taller than some varieties, attaining around 90cm from the ground to the tips of the flower spikes.
Lavender hedges and shrubs of all types require a spot in full sun ideally, a touch of shade during part of the day is ok, but no more.
Whether you intend to grow Lavender Grosso as individual plants or as a hedge, it is important that the proposed site has good drainage. Lavenders suffer from few pests and diseases other than those encouraged by winter waterlogging. If the soil is heavy it pays to dig in some coarse grit to improve the drainage, planting your Lavender Grosso hedge on a shallow mound will also help in these conditions. (If the drainage can’t be improved, in all honesty you would be better to avoid Lavender hedging plants altogether, perhaps choosing an alternative from our list of hedges for wet soil).
When planting a Lavender Grosso hedge we recommend adding a small and sparing amount of Bone Meal fertiliser, well mixed into the soil. Using our Rootgrow mycorrhizal fungi, added directly in contact with the roots can be a great aid to establishment giving your Lavender Grosso hedge the best start.
We normally advise applying a generous mulch to newly planted hedges, Lavenders are a notable exception as they hate the moist conditions created which can lead to leaf and root diseases.
Trimming a Lavender Grosso hedge is the surest way of increasing the life span of your plants. We recommend reducing the height by at least one third, ideally by 50% each season when the flowers have faded (so much more than simply removing the spent flower heads). It may appear harsh, but the plants will respond with a fresh flush of healthy growth and a fantastic show of flower the following year. The golden rule with Lavender pruning is to cut only to a point where there are some small green shoots underneath and no further, on close inspection its surprising how hard you can be and how far down the plant this is!
Grosso can often flower well into the Autumn, if you can’t bring yourself to sacrifice these late flowers (which is understandable!) then its better to delay pruning. Simply deadhead the plants in Autumn and leave the major pruning until warmer weather in the spring as growth starts.
As mentioned already, a Grosso Lavender will be very unlikely to suffer from pests and diseases if the drainage is ok to begin with. The beautifully scented foliage conveniently attracts all the beneficial insects like bees and butterflies while repelling all the harmful bugs – perfect!
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