Ask Mr. Smarty Plants

There are three members of the Arisaema genus native to Illinois that have "Jack in the Pulpit" as their common name:

Arisaema triphyllum (Jack in the pulpit)

Arisaema triphyllum ssp. pusillum (Jack in the pulpit) - pictures

Arisaema triphyllum ssp. triphyllum (Jack in the pulpit)

They are obviously very closely related, and it really doesn't matter which one, or another not native to Illinois, you are growing, they pretty well share the same growing needs. From Paghat's Garden, here is a website on the species and sub-species listed above, with pictures. 

From our Native Plant Database page on Arisaema triphyllum (Jack in the pulpit), here are the growing conditions for that plant:

"Water Use: High
Light Requirement: Sun , Shade
Soil Moisture: Wet , Moist
CaCO3 Tolerance: Medium
Soil Description: Humus-rich, moist soils.
Conditions Comments: Jack-in-the-pulpit is an excellent woodsgarden plant, very easy to cultivate and requiring very little care. It thrives under a variety of conditions, but grows most vigorously in moist, shady, seasonally wet locations. A heavy, leafy wintercover should be left in place."

Every resource on these plants that we consulted said that the plants need an acidic soil, which you would ordinarily find on a forest floor, due to the constantly falling leaves of deciduous trees around them. We learned also that these plants go dormant in the summer, with mature plants producing red berries visible in mid to late summer.

We have a couple of theories on why your plant's leaf edges are yellowing. The first is concerning the soil in the pot where the  Arisaema is growing. When leaves begin to yellow on a plant, we usually suspect chlorosis, which means the plant is not getting trace elements from the soil that it needs. A plant needing an acid soil would have great difficulty in accessing those elements, especially iron, in an alkaline soil. If you are using a commercial potting soil, it might very well be that the plant would be better off in the ground itself, which is probably more suited to an acid-loving plant. Our second theory has to do with the dormancy of the plant in summer. It could possibly be that the dormancy is beginning in that plant, and the yellowing of the leaves is a natural part of that process.

We would suggest that you just keep an eye on the plant, and if you feel the pH of the soil in the pot is questionable, transplant into the native soil at the appropriate time.

Arisaema triphyllum

Arisaema triphyllum

Arisaema triphyllum ssp. triphyllum

Arisaema triphyllum ssp. triphyllum