Long, hot, dry spells followed by heavy rain and cooler temperatures confuses plants and can often lead them to bolt. They haven’t been getting enough water and they respond to a perceived drought by producing flowers and seeds to reproduce and survive. Equally, a sudden cold spell can trick plants into thinking autumn has arrived so they start to produce flowers and seeds.
The first step in prevention is knowing which plants are most likely to bolt. These include:
- Rocket
- Pak Choi
- Tatsoi
- Lettuces
- Broccoli/Calabrese
- Cabbages
- Coriander
- Parsley
The second step is to try and create a consistent temperature and moisture content of the soil. This will alleviate the problems of hot or cold spells. The best way to do it is to add a good layer of mulch (leaf mould works really well) around vulnerable plants to keep the soil from drying out and to encourage a more consistent temperature.
If plants have already bolted (and this is fairly normal so don’t feel bad if they have) then you can always try again a little later on in the year – Pak Choi and Wild Rocket will do really well planted in late August and September for example – or planting again this month but putting in some methods of prevention as described in this post. You could also try planting them in a slightly shadier spot so that they don’t get the full heat of the midday sun.