Isolation distance is what keeps onion seed true-to-type

Onion is a cross-pollinated crop. If a neighbouring plot of a different variety flowers at the same time, bees and wind will mix pollen. The bulbs you harvest next season will not match the tag, even if the seed looked clean in the pouch.

We raise onion seed on contracted farms under a set isolation distance and a roguing schedule. Off-types — plants that bolt early, sit the wrong colour, or throw a different neck — are pulled before flowering. That work is why a packet can say true-to-type without hiding behind fine print.

For growers multiplying their own onion, the same rule applies. Know what is flowering in the next field. If you cannot get distance, do not save seed from the edge rows.

Dealers who want a consistent bulb size for a mandi should ask which isolation block a lot came from. We print the batch code so that question has an answer.