Who celery before 15. May plants, must expect a lot of shooting in bad weather.
To be on the safe side, you should wait until the end of May to plant. Then the floor is already sufficiently warmed up, which contributes significantly to the rapid growth, because every stagnation in growth increases the risk of bolt formation. Celeriac is planted flat, because otherwise there will be no normal tuber formation. The base of the petioles must be above the ground. The tubers then grow halfway out of the ground and do not form roots on this part. Planted deeper, Roots often develop on the upper part of the tuber as well, which affects the quality.
