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Irises are Beauty & Diversity

Irises are early blooming perennials that are easy to grow and very hardy. They come in many varieties of colors, shapes, styles, and sizes.

There are many varieties of Iris Flowers. They can be easily categorized into 3 primary groups of flowers:

  1. Bearded Iris Flowers
  2. Beardless Iris Flowers
  3. Aril Iris Flowers

[1] Bearded Iris Flowers

These irises have the appearance of bushy beards on each of the lower petals (the falls) of the flowers. They are native to Central and Southern Europe and have been introduced to most of the rest of the world. Within the Bearded Iris group of irises are the following types:

Intermediate Bearded Iris: These irises reach a height of between 16-28 inches tall, is one of the earlier blooming irises, and blooms in many colors and patterns.

Border Bearded Iris: This iris is a smaller version of the Tall Bearded Iris and grows to heights of between 16-28 inches. Their blooms are smaller with round, ruffled petals.

Miniature Dwarf Bearded Iris: This is the smallest of the bearded irises reaching heights of 2-8 inches. They are the earliest iris to bloom and do well in rock gardens or as ground cover.

Irises are Beauty & Diversity

Standard Dwarf Bearded Iris: These irises reach heights of 8-15 inches and bloom fairly early in the season with many different colors.

Miniature Tall Bearded Iris: These get taller than you might expect with miniature attached to its name. They reach heights of 16-26 inches and are dainty with smaller blooms in many colors.

Tall Bearded Iris: These reach towering heights for bearded irises at 27-40 inches tall. Because of their height, and stalks that have many buds, they make good flowers for vases and arrangements.

[2] Beardless Iris Flowers

These irises are primarily native to Asia with a variety that is also native to Western Regions of the United States and Pacific Coast Regions. Within the Beardless Iris group of irises are the following types:

Pacific Coast Native Iris: These are the last grown iris because they are very intolerant of climates except in the Pacific Coastal regions. They reach heights of 1-2 feet and bloom in many colors and patterns.

Japanese Iris: These irises produce some of the most amazing flowers of all iris types with huge blooms that are ruffled and flat. They usually produce a marbled gray or white flower.

Siberian Iris: These irises need colder temperatures and wet conditions to produce at their best. They reach heights of 2-4 feet and have mainly blue, violet, or white flowers.

Louisiana Iris: These irises are native to the American Gulf Coast and like wet and acid soil conditions in the spring and are brightly colored.

Spuria Iris: These irises grow to heights of 2-5 feet with very attractive foliage to go with blooms that remind you of orchids. Their flower colors range from white, yellow, blue, wine and brown.

[3] Aril Iris Flowers

These irises are very beautiful with a wide range of colors. They only grow well in the warmest and driest regions so they can be very difficult to grow. Fortunately, they have been crossed with common bearded irises and there are versions available that can be grown in multi-regions.

Aril irises have beards but are not classified in the bearded category because they are very different looking. Their beards would be called scraggly if on a person. This is more than made up for with spectacular beauty.

Soil Basics of Irises:

Most irises need very well draining soils with a coupe of exceptions including the Louisiana and Japanese irises that do well in wet soil. When preparing the soil use organic matter and consider raising the beds for better drainage.

Irises are Beauty & Diversity

If you use manure it needs to be aged for at least a year so it will not severely damage the rhizome and potentially cause bacterial soft rot. Fertilizing should be done when preparing the soil for planting with a ratio low in nitrogen and high in phosphorus and potassium (5-10-10 for example).

Note: When fertilizing don’t let it touch the rhizomes or you risk burning them. It is always better to under fertilize than to over fertilize.

Additional Notes on Planting Bulbs & Rhizomes:

Planting flower bulbs is quick & easy, and nearly foolproof. They are beloved by both beginners as well as master gardeners because the gardening effort will be more towards design and less of hard work.

When to plant flower bulbs:

Remember first to consult the USDA Plant Hardiness Zone Maps. This is the standard and shows you the best time to plant every kind of flower.

Bulbs should be planted as soon as the ground is cool. This could be around the time of the first frost and when evening temperatures average between 40 to 50 degrees F.

Remember that spring flowering bulbs like tulips, crocuses, daffodils, etc, need a period of cold to produce the best flowers.

* Plant at least 6 weeks before the ground freezes to allow for good root development.

* You can store bulbs for a month or so if kept in a cool & dry place between 50-60 degree F.

Note: Keep the label… many bulbs look alike. Also, you should read the label for directions specific to a particular bulb.

Where to plant flower bulbs:

Flower bulbs can be planted nearly anywhere in your garden as long as the soil drains well.

* Avoid areas where water collects like at the bottom of a hill.

Bulbs like a lot of sun so if you have a choice use your shaded areas for other types of flora.

How to plant flower bulbs:

Start by digging the soil in your flower bed so it’s loose and workable.

For the best show of flowers:

* Plant bulbs in clusters versus thin lines or one at a time.

* Plant your high bulbs in the back & lower flowering bulbs in the front. To find the timing of blooms & their flower heights please see our section on bulb types.

* You might consider planting a mix of bulbs that flower at different times. By doing this you will have flowers all season long.

Organic Matter: Especially when starting a new garden, the addition of organic matter such as peat moss or compost is a good idea.

Direction of Bulb: When putting the flower bulb in, make sure to plant with the pointy end upward (even if you do this backwards, in most cases the flower will still find it’s way topside). Tip: If confused on direction, just plant the bulb on its side & it will right itself.

Depth: Plant larger flower bulbs about 8 inches deep and smaller bulbs around 5 inches deep.

Spacing: Space large bulbs 3-6 inches apart and smaller bulbs 1-2 inches apart.

Fertilizer: Think of flower bulbs as built-in storehouses of food. Because of this no fertilizer is needed for the at least the first year.

For perennial bulbs that will come back year after year, you will do the following:

* Spread an organic fertilizer such as compost or rotted cow manure, or

* Apply a slow release bulb food on top of the soil.

Note: Do not mix a fertilizer in the planting hole because it could burn the roots.

Pest & Problems with Irises:

Special Note Before Reading this Section: The following pest and diseases are common to many plants. They are just part of the gardening experience and should not be feared. There are plenty of pesticides and fungicides on the market that take care of problems in the garden.

Iris Borer: This pest is a worm that crawls up the iris leaves and chews its way down to the rhizome root system. Once at the bottom, they can eat until the rhizome is a hollow shell. The iris borer over-winters as an egg attached to the iris leaves.

You can remove the iris borer by digging up the rhizomes, removing them by hand, and then replanting them. An easier method would be to treat the leaves in the springtime with an insecticide. Read the label to find out if it covers the iris borer and also to follow the safety instructions for use and application amounts.

Aphids: These are small insects that attack many plants including irises.

Iris Thrips: The larve of the thrips pierce the surfaces of young leaves and suck the juices from them.

Soft Rot: Irises can also be plagued by a bacterial soft rotting of the rhizome. This occurs at places where the rhizome is damaged and can also be a result of iris borers. One way to rid an iris of this is to scrape out the affected area, let it dry out in the sun, dip in an approximate 10 % mixture of household bleach, rinse off well, let dry again before replanting.

Poor Flowering: This is usually due to planting irises in excessive shade, using too much fertilizer, planting the rhizomes too deep, or allowing the irises to become overcrowded.

Fungus Rots: This usually occurs in warmer humid climates with the fungus attacking the iris at or near the soil surface.

Rust & Bacterial Leaf Spot: This weakens but rarely kills the iris.

Nematode Infection: Two versions of this are root-knot nematodes and meadow nematodes. They are microscopic worms that attack many plants including irises.

Mosaic: This is the most widespread iris disease and it is caused by a virus transmitted by aphids.

Irises are wonderful flowers with character and beauty. They are hardy perennials and will provide you with years of enjoyment.