“I was wondering (and hankering for some rhubarb crumble) when should I stop harvesting. The plants still have loads of stalks but I have heard that after a certain point the stalks become poisonous and can’t be eaten?”
The sweetest stalks are the first few of the season in March. You can harvest throughout the season but at some point you should stop harvesting in order to give the plant time to settle down and get strong to get through the Winter. August Bank Holiday is traditionally the final harvest in our house.
After the final harvest leave the plant alone to recover from giving up so many harvests. The following November I put a few handfuls of pelleted manure around the plant and lightly fork it in with a hand fork.
Throughout the season when harvesting the stalks don’t forget that rhubarb leaves are poisonous. I remove them while still standing by the plant then place them around the crown and let them rot and in time, feed the plant.
In the first year of growing rhubarb only take a few, say 3 or 4, stalks. You want to give the crown time to bulk up and removing a lot of stalks in the first year will only weaken the plant. Ideally this should be repeated for the second year and take a full harvest in the third year onwards.
Rhubarb crowns establish themselves deep in the soil and its difficult to remove an established crown. Plant in a permanent position.
When nature calls I feed my rhubarb with urine. Just pour it over the plant and watch it grow! It really does make it much bigger and stronger. I don’t dilute it, I just pour it straight over the plant.