Irises are a beautiful addition to any garden. With their long, graceful stalks and brightly-colored flowers, they’re sure to add a splash of color to any landscape. What’s more, they’re perennial plants, meaning that they come back year after year and multiply on their own. So how can you make the most of this hardy flower in your garden?
One thing to keep in mind when planting irises is that they come in a variety of colors. This means you can choose the right hue to match your landscape or flowerbed. Bearded irises also come in a range of sizes, so you can pick the one that best suits your needs.
Bearded iris plants provide months of colorful landscape interest, regardless of what zone you live in. These hardy perennials flourish in USDA Zones 3-9, where winter temperatures dip below freezing and allow the plant to go dormant before next year’s growth. Depending on the type of bearded iris, they can be in bloom all the way into June. Some types even rebloom in late summer and fall. So whether you’re looking to add a pop of color early in the spring or want to extend your garden’s color show well into summer, bearded irises are a great choice!
Iris are a diverse group of plants that come in three main categories: bearded, bulbous and species. Bearded iris get their name from the soft bristles on the lower petals of the flowers and come in a vast array of colors and patterns. They have a long bloom time and can be found in every color except fire-engine red.
Growing Tips for Iris
No matter which varieties you choose, you can help bearded irises thrive in your garden using a few simple tips. Follow these tips for the healthiest plants and most vibrant blooms:
- Bearded irises should be planted in full sun
- They will also require well-draining soil
- In early spring, fertilize with an all-purpose fertilizer
- Water your irises regularly, and even more so during hot weather
- You can encourage new blooms by ensuring you deadhead spent blooms.
Late summer is the best time to plant them, and make sure they get at least six hours of sunlight every day. They also need well-drained soil. Although they need at least six hours of sunlight, a full day is even better because this will keep the rhizomes dry. Rhizomes are the rootlike, fleshy structure that you find at the base of the plant.
Preparation is key so you need to prepare their beds. Apply a low-nitrogen fertilizer firstly in early spring, then again just after they bloom when the rhizomes are forming the following year’s flowers. You only need to water them if you are transplanting them, or if the weather is extremely dry.
Bearded iris require good air circulation, so plant them a minimum of 16 to 18 inches apart so you give them room to breathe. Naturally, if you have dwarf irises, they will need less space, and tall bearded iris varieties will require more space).
Because mulching is designed to help soil retain moisture, do not mulch. The rhizomes will rot if there is too much moisture.
After once the iris blooms have faded, remove the seedpods that have formed. This will help prevent the seedlings from choking the surrounding soil. Seed formation also saps the energy that is needed by the leaves, roots, and rhizomes.
To reduce the chances of overwintering pests and diseases, prune back the foliage in the fall.
Get into the habit of dividing. Clumps of bearded iris plants should be divided in late summer every three to four years.
Dividing Bearded Iris
As the bearded iris matures, the rhizome multiplies which increases the production of leaves and flowers. However, over time, the original rhizome dies off and this can slow the speed of new bloom production. For the newer rhizomes to have the space to fully develop, it’s necessary to divide the plant and remove and replant the newer rhizomes.
You need to divide bearded iris in the late summer once the weather starts to cool down. You can use the same process that is used for other plants that produce rhizomes, such as lily-of-the-valley, toad lily, dahlia, bergenia, and canna.
Here are the steps for successful division of your bearded iris:
1) Dig up the clumps with care using a spade or garden fork. You need to be careful not to damage the rhizomes any more than necessary.
2) Pull the rhizomes apart with your hands in order to divide them. You may need a sharp knife to separate the smaller rhizomes from the main rhizome. If this is the case, use a 10% bleach/water solution to dip your knife into between cuts. This ensures that you don’t spread any diseases that may be present to the new rhizomes.
You can remove large, older rhizomes that have no leaf fans. Bear in mind that a good rhizome will have one or two leaf fans, healthy roots and will be about the thickness of your thumb.
3) You will need to inspect each of the rhizomes and check for a plump, white worm known as iris borer. It needs to be destroyed if you find it. Wash the soil off the rhizomes so you can get a really good look at them. Some gardeners prefer to wash their iris rhizomes in a 10% bleach solution to help protect against disease, however this won’t help for plants that may be already rotting. Any smelly, soft rhizomes should be discarded, together with any that feel hollow, are lightweight, or look dead.
4) Cut the Leaves
In order to reduce the stress the plant goes through while concentrating on regrowing new roots, clip off the leaf blades. They should be 4 to 6 inches long and this means the plant doesn’t have to try and maintain long leaves.
5) Plant the Divisions
Ensuring that you set the rhizome higher in the planting hole than the fine roots, replant the divisions. The fine roots should be fanned out and a small bit of the top surface of the rhizome should be visible at the soil surface.
6) Plant the Remaining Rhizomes
Space the plants between 12 and 18 inches apart, remembering to plant closer together for dwarf varieties, and father apart for the larger plants. Plant the rhizomes so the fan of leaves faces the same direction for the best display.
When planting bearded iris rhizomes, make sure you water them well, but discontinue watering unless the weather becomes dry.