Planting for Moist Shade - Part 3: Japanese Iris

» Tim_Dutton - Japanese Iris

It's been weeks since I looked in at Suite101, Having just read this article Marge, I can tell you that all the Japanese Iris that I have in my bog garden are quite happy with wet feet all year round. They do not seem to flower well if too shady, so I have them planted in the sunniest spot, but still need to cut down a few shading trees that are due for removal. They grow in just about the wettest part of the garden, a solid clay pan in a bit of a dip, covered with a few inches of very rich compost. These irises have to be fed, so the compost needs topping up every year. I use well rotted horse manure. As we have our own horse, this is not a problem! Then the compost is covered with a couple of inches of wood chip mulch that I make. Over a 12 month period the mulch will all rot down, so the depth of soil keeps increasing over time.

This particular bog garden is pretty well sheltered, little wind, little frost, but gets a lot of rain in the winter. The irises thrive in these conditions.

Two other interesting plants that you may have come across for wet places, both of which seem to grow in shade or sun. You need space for both though.

The first is the marsh marigold, Caltha palustris. This will grow in standing water or just very wet soil. It has big bright green rounded leaves, large buttercup yellow flowers in spring, and spreads by sending out runners. It forms an ever expanding clump, but is easy to reduce in size. In my garden it is evergreen, but in colder climates is said to be deciduous or semi-evergreen.

The second is the Giant Hogweed, Heracleum mantegazzianum. This is a plant that you grow for a striking impact. It is a perennial, but flowers for the first time in its second year. I have a couple in flower at the moment (late spring here) which self seeded from plants grown two years ago (which then died - perhaps they are biennial), and they have large flat umbels of white flowers. Mine are about 18 inches to 2 feet across, but they are supposed to be able to get to 5 feet across!!! The flowers are so far above your head that you really need to plant them at the bottom of a slope and look at them from the top to see the flowers properly! My plants are only (?) around 10 feet tall at the moment. Two words of warning. They self seed very easily, so don't keep too many, and the plant contains a poison that can cause the skin to burn when exposed to sunlight. Try not to brush against them. Of course, mine just happen to be right next to the path. Bad planning.

I just love big perennials. I have some Gunnera tinctoria and Cynara cardunculus (cardoon) as well, both of which get pretty big.

-- posted by Tim_Dutton