Answer: First of all, counting back from Halloween, giving Lumina 90 days (3 months) to mature would mean you would, theoretically, need to plant them August 1, giving them all of August, September, and October to grow. But in reality, you need to take into account other factors.
Most pumpkin seeds should be sown in the garden as soon as all danger of frost has passed and the soil has warmed up in the spring. Remember that up to June 20 or 21, the days (hours of daylight) are getting progressively longer; after that, they begin to shorten. You want as much sunshine as possible on those developing pumpkins! The days-to-maturity numbers assume that the plants are growing during the peak of summer and under the maximum amount of daylight.
One of the great things about pumpkins is that they keep well. So even if you get mature pumpkins in late September or early October, if you keep them in a cool place they will keep just fine until Halloween. I would rather plant early, rather than too late and risk having green pumpkins (or no pumpkins!) for the holiday. I'd go ahead and plant now.
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