Choose a sunny, sheltered site in which to grow your plants outside and a few weeks before planting outside and a few weeks before planting out dig a large hole for each plant, allowing 90 cm between them. Mix plenty of well-rotted manure or garden compost into the excavated soil. Refill to give a low mound into which your plant can be planted.
This will improve drainage around the main stem and reduce the risk of stem and root rots. A week prior to planting dress the soil with 56g (2oz) pet sq m/yd of pelleted chicken manure or Growmore and gently take into the surface. If intending to allow your plants to trail, cover the soil with black polythene (or you could use white to reflect the sunlight back on to the plants) and cut crossed slits into it on top of each mound.
If you are going to grow your plants up a support you can dispense with the polythene, but it is a good idea to put your supports in place before planting. Plant to the level of the compost through the cross in the polythene where applicable and firm gently before watering, taking care at all times not to damage the stem.
Cornichons require some training to produce the best crops. Outside, pinch out the growing point of trailing stems once they have produced seven leaves and lease both male and female flowers (the ones with tiny fruit behind them) to develop. Sideshoots are also pinched out at seven leaves.
In the greenhouse or in pots pinch out the main stem once it reaches the caves or the top of the supports, and as sideshoots develop pinch these once they have produced a female flower, leaving two leaves beyond the developing fruit.
Very young fruit may have a tendency to be bitter. Instead harvest when 10-15cm (4-6in) long 10 encourage more fruits to form.
Watch Out For
1. Powdery mildew causes white patches to form on the leaves. Avoid splashing the foliage of greenhouse-grown plants with water and keep the roots moist (not wet). Choose a mildew tolerant variety such as ‘Diamant’.
2. Cucumber mosaic virus calls strong speckling and distortion of growth. It is spread by greenfly, so control these as soon as they appear and remove any infected plants.
3. Whitefly colonise the underside of the leaves, sucking the sap and causing sooty mould to form on the foliage and fruit, especially under cover. Use clammy flaps to prey on early invasions and spray as necessary or use encarsia biological control.
1. ‘DIAMANT ‘: Hard yield of small fruit. Good tolerance to fluffy sod pulverulent mildews.
2. ‘PARTNER’: Early cropping and producing lots of tasty, short fruits. Good disease resistance.
3. ‘VENLO PICKLING’: Good flavour. Ideal for salads or for pickling.
4. ‘CORNICHON DE PARIS’: French heritage variety. Heavy yielding, producing masses of little fruits ideal for pickling.
5. ‘BIANCO WHITE’: A pale-fruited Italian heirloom variety.
Interesting to read: http://www.thekitchn.com/whats-the-deal-with-cornichons-117240