Iris ensata, Iris laevigata and Pseudata in Containers

By Chad Harris

Iris ensata and laevigata have been cultivated with container culture for centuries. In Japan several different flower forms and indoor display regulations were specifically formatted for container growing of Iris ensata. You may also find that growing these water lovers and the new hybrid “Pseudata” in containers easier, as you will have better control of the rich moist soils that they demand.

Soils: A good soilless container potting medium should be used. Here at Mt. Pleasant Iris Farm we use ‘Miracle-Grow’ with 6 month feeding. We use it not only for the patio container, but also for the germination of the seed of our breeding lines.

Container: A one gallon container is the minimum, for a single or double fan plant. This will keep the plant for one growing season, requiring yearly transplanting.

One gallon containers need to be transplanted yearly for the health of your plant and container.

I highly recommend that a larger container be used; three to five gallon will be optimum for two to three year growing seasons. Note that the size of containers for starting seed is a one half gallon.

Seedlings in half gallon containers.

The seedlings are grown for one to two years in this size before being transplanted out to the field.

Light: Full sun with a minimum of six hours to bloom properly. Areas with more intense sun and or heat will find that morning sun and afternoon shade will benefit both the plant and the bloom. While the plant wants to be in the sun the root zone needs to be kept cool. With a large collection this can be achieved placing the containers close to each other while shading the outside containers with planks boxing them in. The smaller collection the shading can be achieved by double potting.

Shading the poly container by double potting.

Placing the smaller container into a larger heavier decorative ceramic container, this is the method that we use on our patio. One could also use a very large decorative container that could hold several smaller poly or plastic containers. A clump look with many different varieties can be achieved without mixing them up, losing their names.

Iris ensata in containers.

Water: These plants are water lovers and should not dry out, keep evenly moist. During the summer this may demand a daily watering. A deep tray filled with water will allow the plant to stay completely hydrated for longer periods of time. For larger collections a child’s wading pool could be used, or a box made of planks lined with a pool liner. Drill holes into the sides one to two inches from the bottom for overflow drainage. The rhizome of the plant should be above the waterline, this is critical for Iris ensata especially during the winter months. Iris laevigata can grow with its crown under water with two inches covering; however it is best to start the new plant above the waterline to help prevent rot. You can gradually submerge the plant after new growth appears. Pseudata (being half Iris ensata) I would play it safe and would grow as Iris ensata, with the rhizome above the waterline.

Iris ensata in containers.

Fertilizer: Use a slow release for acid loving plants mixed into the potting mix. Or use a water-soluble and add directly to the water. Do not use Bone Meal in any application as this will change the PH and can kill these acidic loving plants.

Iris  laevigata in patio containers.

Transplanting: Repot right after bloom, discarding the old soil, roots, and rhizome. The new rhizomes are in a full growth mode at this time through the summer and fall until the winter sets in.

First frost: time to cut the foliage back.

Winter Care: After a light freeze, cut all of the foliage off at container level. Mild winter areas (USDA Zone 8-9) containers can remain out in the pools and or above ground. Colder climates the containers should be lifted from the flooding pools or trays and buried in a prepared bed with a good mulch cover. In the spring return the containers to the flooding pool, lightly fertilize after new growth starts to appear.

For the many that have tried to grow these water lovers in their garden and have failed, give container growing a try. It is definitely easier to maintain their demanding cultural needs of a rich moist soil. You may also be able to push the envelope of where they have not been grown before surprising your iris club at your next show. Give one a try.