"How to propagate Jack in the Pulpit (Arisaema)"
by Tony Avent
Jack in the Pulpit Propagation
Jack in the Pulpits (Arisaema) can either be propagated from seed, offsets, or by cuttings, although seed is most prevalent. As mentioned earlier, you will need either a monocious species (male and female on the same plant) or a diocious species that is producing both male and female flowers to be sure to get seed. Most seed ripen from early fall to late winter, depending on the species. Typically a red coloration is an indication of ripe seed, although many species can be picked green if the entire seed head is harvested. These seed will usually ripen indoors if the developing embryo are already well developed.
After the seed are harvested, they should be cleaned first (the pulp contains a germination inhibitor). The easiest way to clean arisaema seed is to put the ripe seed into a ziploc bag and "squish" the pulp from the seed. Important safety tip...the oxalic acid from the sap of the fruit can cause severe skin irritation and numbness, so wear plastic gloves. After adequate squishing has been complete, pour the mess into a cup of water. Decant the pulp several times, and you will quickly have a cup of clean seed.
Arisaema seed can be planted in a container of potting soil indoors immediately after cleaning. The seed should be covered lightly with potting soil. Arisaema seed will usually sprout within 4-6 weeks and will proceed to grow for up to 2-4 months. At this time, they will appear to slowly turn yellow and die. Fear not, for they are only going dormant. Some species have the strange habit of going directly from seed to small corms, known as protocorms.(P. Bruggeman - personal communication). These protocorms don't produce foliage until after dormancy. When dormant, arisaemas in containers must not be kept wet...this is certain death for most species. I keep my plants in containers and water only when the soil gets bone dry...about twice a month.
These arisaema seedlings can like this until winter or planted immediately in prepared ground beds. After a cold period, they will again resprout. Some of the warmer growing species will actually resprout during the summer and put on an extra growth cycle (especially Arisaema consanguineum). To squeeze out an extra season, the dormant plants can be refrigerated for 3 months during the spring/summer. This can be accomplished in the container (if your refrigerator and spouse will allow) or by placing the tubers in a ziploc bag of slightly moist peat (easier to store in the refrigerator). After this time, they will resprout and can often be forced into two seasons of growth during a calender year.
From seed, expect it to take 2-4 years to have a flowering size plant...depending on species. Some species such as Arisaema franchetianum, Arisaema candidissimum, Arisaema ringens, Arisaema tortuosum, and Arisaema taiwanense get quite large from seed during the first growing season. Others such as Arisaema sikokianum remain much smaller after the same period.
The other extremes are species like Arisaema elephas, which only sends out a root during the first season. Only after a dormancy period will the new leaf emerge. This could have been easily predicted due to the tiny size of the seed in this species, as compared to the relatively large seed size of those mentioned above.
While seed can be a challenge for some gardeners, division of offsets is much easier...provided your arisaema produces offsets. Some arisaemas are solitary like Arisaema sikokianum, while others offset freely like Arisaema ringens. Arisaema species that multiply well from offsets include Arisaema amurense, Arisaema candidissimum, Arisaema concinnum, Arisaema consanguineum, Arisaema exappendiculatum, Arisaema fargesii, Arisaema franchetianum, Arisaema kiusianum, Arisaema saxatile, and Arisaema thunbergii. The small offset bulbs/runners can be snapped off and replanted. While some gardeners like to wait until fall to divide their arisaemas, I have found that it works equally as well to move and divide arisaemas when they are in full flower.
Tissue culture was a difficult nut to crack with arisaema, complicated by their complex dormancy patterns and difficulty of sterilization. Hans Hansen of Walters Gardens in Michigan was the first person to commercially propagate arisaemas from tissue culture.
Plant Delights Nursery has done some inital work with arisaema from cuttings. In their limited trials, they have had success with both leaf and petiole cuttings with some of the tropical species. More work needs to be done, but they expect arisaemas to be similar to Amorphophallus in their ability to be rooted from leaf cuttings.
So now that you know how to propagate your Jack in the Pulpit, go forth and multiply!
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