Last year I sowed some ‘Cathy’s Ghost’ lupins in preparation for planting an area of the garden that will be strictly yellow and white. No gold, mustard or tangerine – just lemon yellow and white. Don’t ask why, I just fancy the idea – I am calling it my ‘lemon meringue’ garden. I sowed the lupins in August and the plants were happy in cell trays over winter, then I potted them into 10cm diameter pots in early spring and then they went into the bed, fifteen in all. At first things were fine. I crossed my fingers that the rabbits would leave them alone and luck (and chilli powder) was on my side and they grew. Now they are in bloom and although one has a slight pink tinge (things are always variable from seed) I am fairly happy apart from the fact that in the past two weeks, when we ‘enjoyed’ dry, hot weather (though not as extreme as the UK and the rest of Europe) they have all developed powdery mildew.
Despite its name, powdery mildew is usually caused by dryness at the roots and is a sign that the plant is stressed. Of course, it is not always possible to prevent it, and some plants (such as lupins) are rather prone to it, but I am a little disappointed. There is no point spraying and, as with all fungal diseases, spraying now will not get rid of it – just prevent further infected leaves.
It is very important to cut off faded flowers from lupins, to prevent seed production and weakening the plant so I will decapitate the offending stems as soon as I can. This will help encourage basal branching and perhaps more, later flowers. Mildew can also be reduced if you feed the affected plant and keep it moist. So when you cut back mildewed delphiniums and lupins, give them a mulch and a good water to encourage healthy new growth.
As I improve the soil, and as they get better established, I hope the lupins will be less prone to this disease but I have a horrible feeling I am going to be haunted by this vision for some time.