Beginner’s Corner: Container Gardening – Part 1, Containers

 by Doug Chyz

Did you come back from your local iris sale with more irises than you have room for in your garden or are you a container gardener already? Are you looking for a temporary home for your irises until you get beds prepared, or would you like to have a few larger containers filled with irises as specimen plantings anchoring walkways or patios? No matter the reason, growing irises in containers is easy. The following are some tips, tricks, and traps for growing irises in containers.

First, you need to consider what the size of your containers will be. You may have locations that allow for very large containers, or you may be restricted by space or even funding. Large decorative containers can be expensive and then you need to add soil to them which is another expense. Speaking from experience, I know that irises can be grown in containers from one gallon in size to very large ones so do not be afraid of using smaller ones especially if you are using them for temporary homes.

A large container makes a great statement

Although I have successfully used one-gallon nursery pots, my preferred size for temporary homes are three-gallon nursery pots. They provide space for the irises to increase and will allow irises to bloom over a two-to-three-year period if you want to keep them in the containers that long. Realize that nursery pots have drain holes and they will need routine watering – read daily during the summer. If you provide a basin under the pots that will hold some water the irises will thank you, but they will still need daily watering during the summer.

You can enjoy irises in containers

I currently live in South Carolina near the coast and do not have to worry much about winter weather. Before moving here, I lived in Virginia with snow, ice, and freezing weather during the winter. My potted irises remained outside all year round. They did fine, but if you live in an even colder climate area you may consider locating the pots in an area where you can mulch around them. You do not have to worry about them being covered with snow; but if you are having a long dry spell during the winter, you should water them. Also, if you had basins under the pots, you should probably remove them for the winter.

Don’t overlook the opportunity to use a large container if you have a place for one or more. I have used them with one variety of iris with several rhizomes to get a nice potted clump effect, and I have used them for several different varieties to include smaller dwarf irises along the outer edges and taller iris or irises in the center. And consider various types: Siberian, Louisiana, or Japanese would make great choices and for those of you who can grow Pacific Coast Natives, larger pots would make great showcases for them.

In Part 2, I will talk about soil for containers, so come back again.

Irises in Containers

by Tom Waters

Irises are not usually thought of as container plants, but they can grow quite well that way, and there are a number of advantages to doing so.

Two Iris pumila cultivars,
'Wild Whispers' (Coleman, 2012) and
'Royal Wonder' (Coleman, 2013),
growing happily in a large container

The irises I choose to grow in containers are mostly dwarf bearded irises and the smaller arils and arilbreds. Tall bearded irises look out of place in even the largest containers, and a light container soil mix may not give them the support they need when top-heavy with bloom. The smaller irises, however, are naturals for container culture. They bring the plants closer to eye level for viewing, and allow them to be moved from place to place for best effect. If attractive containers, like oak barrels or terracotta pots are used, the effect can be quite lovely and dramatic.

There are additional advantages to container culture. I tend to put rare or choice plants into containers when I first acquire them, as it makes them much easier to weed and care for. A small iris that might get lost in an overgrown summer garden and succumb to neglect, is kept safe in a container where it can get the attention it needs.

Two forms of the exotic oncocyclus species Iris paradoxa
in a large container with a gritty soil mix

Arils are another good candidate for container culture in climates where summers are too wet to grow them successfully in the ground. The container can be stored in a warm dry place through the irises' summer dormancy period. It is also possible to provide a coarse, well-draining soil mix that would be difficult to maintain in the open garden.

As a hybridizer working with dwarfs and other small irises, I also appreciate that containers make the blooms more accessible. It's much nicer to pull a chair up to a container than to crawl around on the ground to harvest pollen or make a cross.

Most of my containers are inexpensive plastic models, in the largest size possible (two to three feet in height and diameter). Even the smallest irises enjoy a wide and deep root run. I fill them with various soil mixes, depending on what I have at hand, but I usually use a mix of my garden soil (a somewhat sandy silt) and commercial potting soil, sometimes with addition of compost, coarse sand, or even small gravel. The irises do not seem too picky about the exact composition of the potting mix. I like to use a top dressing of gravel as a mulch. It also looks nice, especially if a few rocks are positioned on top to make a miniature landscape.

Even in a container with enriched soil, irises will not go forever without dividing them and refreshing the soil mix every few years. Keep an eye out for overcrowding or declining vigor. Also, it is important to keep to a regular watering schedule; how frequently you water will depend on your climate, but the only time I have lost an otherwise healthy plant in a container was when I accidentally let it get bone-dry in the summer. Containers are less forgiving in this way than garden soil.

If you've never grown irises in containers, give it a try this year! You may find it offers both esthetic and practical rewards.

Iris reichenbachii blooming profusely in a container