Lavender hails from Mediterranean regions: warm, dry, mineral rich soils. It does not take kindly to heavy, wet ground and damp weather conditions. However some lavenders are tougher and more resistant to adverse conditions than others; certainly there are plenty of varieties to choose from. In some cases I think we expect too much from our lavender. In most cases lavender is not a long-lived shrub, over a period of time it can deteriorate and needs replacing anyway. If it was planted as a seasonal bedding plant or a perennial we would be quite satisfied; because it is a shrub we expect it to last forever.
The fragrance and aromatic quality of lavender make it a desirable plant. It’s a familiar subject with which we have an emotional attachment. The desire to grow it arouses determination in the gardener whether the growing conditions are right or not. First and foremost lavender needs an open sunny position; no half measures. If your garden is shady then forget it or accept that you will have to plant it in flower and throw it away at the end of the season.
Secondly it needs good drainage. If you are on clay which is wet in winter lavender will almost certainly fail unless you take precautions. Adding copious amount of grit to the soil and mulching the soil surface with grit helps enormously. The grit on the surface prevents the rain from splashing soil back up onto the stems and foliage which is often a reason for demise. Also when you plant on wet soil don’t plant too deeply. Try to plant on top of a very low mound so that winter wet drains away from the plant.
Lavender grows best on free draining sandy or gravelly soils and it thrives on chalk. It does not love peaty soils or those that are rich in organic matter. Avoid bulky organic manures and go easy on the garden compost. Use a general slow release fertiliser such as rose food sparingly. This has plenty of potash which hardens up the plant as well as stimulating flower production.
So which variety is the best?
If you want lavender to last then plant a named cultivar of Lavandula angustifolia, the narrow-leaved or English Lavender. This is hardier and more resistant to wet. I would always choose Lavandula angustifolia ‘Hidcote’; it is compact, aromatic deep blue and a great performer which lasts.
I would plant it as young pot grown plants (in the UK these would be in 2 – 3 litre pots, US half gallon). In a bed I would space these 30cm, 1ft or 45cm, 18” apart with the idea that the bed would be pretty well filled in a year or so. You need to prune lavender as the flowers fade from the first year. Cut back to just below the flower stem to encourage new growth before winter. If you want lavender for drying cut earlier. ‘Hidcote’ is one of the best varieties at keeping its dark blue colour and fragrance.
For a hedge plant 45cm, 18” apart and if edging beds do not plant too close to other subjects such as roses. Lavender always seems such an obvious planting partner for roses, but actually no two plants could be less compatible. Both subjects hate competition, roses like heavy, rich soil and plenty of water and lavenders like the opposite.
In my experience if you are planting a bed of lavender or a lavender hedge you must expect two or three failures. I always try and keep two or three plants to fill the gaps. I grow these on in pots filled with loam-based compost. They make good subjects for the patio and they will be at the same stage as the others growing in the open ground.