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Bearded Iris (Iris germanica)
by Fred Davis, MG, Hill Gardens of Maine (To view other articles, click: Archives)

Welcome through Fred's Garden Gate! Iris are one of the easiest perennials to grow. Once properly planted in their permanent location in your garden, they take very little care. Indeed, they can survive almost total neglect, yet reward you with yearly displays of beauty and color. Here are basic planting instructions and some hints and suggestions to get the most out of your iris.

Soil Preparation

Iris require almost perfect drainage. If you have a heavy soil, or it tends to stay very wet, you should consider "raised beds" - at least 6 or 8 inches above surrounding soil - and working in a fair amount of sand so water percolates out quickly. Work the soil to a depth of about 10 or 12 inches. If your soil is acid, add a little lime, adjusting to pH 7-7.5 -- iris may "grow" in acidic conditions, but they'll perform much better in neutral or slightly-alkaline soil. A sample of soil sent to your state's agricultural university's soil testing laboratory will tell you just how much lime to add. The test usually costs about $10 to $12, and collecting/mailing supplies are available through the Cooperative Extension Service. Alternatively, you could test your own soil using one of those over-the-counter kits or "electronic" probe testers...but results vary and may be questionable. Get it done professionally.

Iris will generally do just fine in most average Maine soils, and will thrive without feeding. They will respond, however, to the application of fertilizer--something in the range of 5-10-10 or an organic equivalent is ok, just be careful to avoid heavy applications of nitrogen, as it stimulates soft growth that is susceptible to rot...and that can ruin a good iris bed in a hurry! Spade in some well-decayed compost deeply into the root zone. That will not only provide nutrition but also encourages roots to go deep and make plants more tolerant of hot, dry periods. A little bonemeal down deep will promote strength and heavy bloom the following year. (Bonemeal will continue to positively affect strength and flowering for up to three years...but be forewarned: bonemeal indiscriminately spread around may encourage digging animals attracted by the odor.)

When to Plant

For best results, plant your rhizomes (that's the larger, fleshy part of the root) during late July or August. The earlier you can get them in, the more time they'll have to develop a good, strong root system before winter sets in. Without those strong new roots, they'll have trouble surviving the long, cold northern New England winters and it's likely they'll heave right out in the spring. Divide 3- or 4-year-old clumps about 5 or 6 weeks after the flowers fall--usually about the first of August in USDA Zone 4.

Where to Plant

In a sunny, well-drained spot. They really need at least a half days' worth of sun, never deep shade. Water should never stand in your iris bed. Stone walls are an ideal setting for iris.

Depth to plant

Place your rhizomes just below the surface of the ground with the roots well spread out underneath so the top of the rhizome is within reach of the warmth of the sun's rays while the roots beneath are in moist (not soggy) soil. Be sure to firm the soil around each rhizome when planting. Follow ordinary good-gardening practice of watering them in right after planting...but don't make a mud-hole. Remember: don't completely cover the rhizome...you'll end up with rot.

Cultivating

The feeding roots of iris are right next to the surface, so you should only cultivate very shallowly--just barely scratch the surface. Remember that iris rhizomes need to be exposed to the sun, so keep weeds and other nearby plants away from the base of your iris. Don't allow soil or old, dead iris leaves to cover the rhizome. Clean cultivation is one of the keys.

Watering

A common mistake is to give iris too much water. When first planted, water the rhizomes thoroughly and then every couple of days over the next 2 or 3 weeks so new roots can develop. Don't expect big surges of luxurious growth right away--that won't come until next spring. If the weather turns hot and very dry, water occasionally, being careful not to create a mud-hole... they may rot!

Winter Protection

After the first hard frost, trim the remaining leaves back to within about 5 or 6 inches above the rhizome and mulch with at least 4 or 5 inches of some loose, dry, weed-seed-free material. Some of the big growers recommend straw. We like pine needles because they "breathe" and don't mat down and smother like leaves, grass clippings or shavings. In the spring, after the ground thaws, just remove the pine needle mulch to allow daylight to hit the top of the rhizomes and watch Nature do it's thing! The greatest danger to iris during the worst of winter is alternating freezing and thawing that happens to plants that aren't properly protected.

A caution: pine needles are strongly-acidic, and can shift soil pH markedly. Be sure to completely remove them in the spring...and re-adjust pH back to neutral (7.0) with some fine-ground limestone.

Sources

Most local nurseries and garden centers carry at least a few bearded iris. Look them over carefully for signs of rot (soft, "squishy" and stinky rhizome) and iris borers (the larval stage of a moth that bores a small hole in the stem just above the ground then burrows into and eats the rhizome).

A tip: move the surface soil away from the partially-exposed rhizome. Look for soft spots—and sniff. If it smells like rotten potatoes, put the container back where you found it. I've been known to take such a specimen directly to the nurseryperson — or nursery manager. They won't like being shown something that they, themselves should've spotted first...but you've made him or her aware of a serious flaw in their nursery stock maintenance and marketing methods... and quite possibly will have saved the next potential buyer considerable angst.

A good source of strong, healthy (and guaranteed) rhizomes is Schreiner's Iris Gardens, 3625 Quinaby Road, N.E., Salem, Oregon 97303-9720. www.schreinersgardens.com/ gets you to their informative site.

Wherever you decide to buy—whether online or by mail—first check what other customers have to say about their experiences with that company. You'll find an extensive list of mailorder suppliers at http://davesgarden.com/products/gwd/ (it used to be called "Garden Watchdog). And don't be afraid to post comments about your experiences while you're there.

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