In Essex County, New Jersey, you can visit the Presby Memorial Iris Garden, a living museum and iris garden on 6.5 acres. A Victorian house surrounds the gardens. Visitors can also learn about the fungus and thrips that infest iris plants.
Preparing iris garden beds
Before you plant irises in your garden, you should prepare the beds for them. Iris need to be thinned every three to four years to prevent them from becoming overcrowded. Irises that are overcrowded will not only have poorer blooms but also crowd out other species and increase the risk of disease. You can thin clumps by removing the old rhizomes from the centers of the plants, or you can dig up and replant large rhizomes. You should also keep your iris bed free of debris and prune bloom stems back to the ground after flowering.
Irises are easy to grow, but they require a little preparation. You should remove any grass that has sprouted in the bed and dig down about 12 inches. This will loosen the soil and cut off the roots, which can cause weeds later. Then you can plant the rhizomes in new soil.
Iris rhizomes should be planted at least 12 inches apart, although closer spacing gives an immediate effect. If you plan to plant several rhizomes, try to plant them in a circle. If you plant three roots in a circle, you can get a clump effect next year. If the weather is extremely hot, try to shade the area for a couple of days before planting.
Another thing to remember is that iris eggs are laid on iris leaves, so keeping your iris garden beds clean is important. In the Fall, you should remove the leaves and any other debris that may have been left behind by the previous season. This will keep the iris beds free of debris and prevent disease-causing organisms.
Ideally, you should plant irises in the late summer or early fall. This way, they will have time to establish their roots before the summer season ends. However, if you live in a hotter climate, you can plant irises later in August. Regardless of your climate, ensure your iris garden bed has proper drainage.
The springtime blooms of irises make your garden a showpiece. Their large, ruffled blooms and green stalks are a beautiful addition to your garden. Various irises are available to grow in your garden, including bearded irises and stinking iris. Bearded irises are hardy in USDA zones three through ten, while stinking irises are hardy in USDA regions six through nine. The latter is so named because of its smell. Deadheading is also an important step in growing the iris.
Iris borer
The Iris borer is a pest that will damage your iris plants. Its larvae live in the soil surrounding irises and lay eggs on dead leaves and plant debris. Once they hatch, the larvae grow to about two inches in length and tunnel into the leaves. They emerge as moths in late summer and fall.
Fortunately, the Iris borer can be managed in a variety of ways. The first step is ensuring your iris gardens are clean and debris-free. Cut back foliage after the first frost, remove rhizomes, and remove other iris plants nearby. You may also want to remove the leaves and plant debris from other plants as these may contain eggs of the Iris borer.
Adult Iris borers emerge in August and fly only at night. Females lay their eggs on old iris leaves and other debris on the ground. After a couple of weeks, they emerge as adults and begin to lay their eggs. They also cause permanent damage to iris plants by allowing bacteria to grow in their holes.
The best way to control the Iris borer in your iris garden is to treat the plant with an insecticide. Pyrethrum can be applied to the leaves and base of your plants, and the insecticides azadirachtin and third can be applied directly to the rhizome. Alternatively, you can treat the plants with insecticides like methyl nonyl ketone. These chemicals kill the larvae before they can pupate and cause further damage.
The larvae of Iris borers hatch in spring and feed on the leaves. The larvae bore down to the rhizomes of iris plants and left wet streaks on the leaves. This can eventually lead to rot. It may also cause the rhizomes to die.
The best way to control the Iris borer in your iris garden is to treat the plants in their early spring and summer. This can be accomplished with insecticides and insecticidal soap. Just be sure to follow the instructions on the label.
Iris thrips
You can do several things to prevent Iris thrip in your garden. The first step is to find the source of the problem and treat it. Often, the source of the problem is the presence of too much nitrogen in the soil. If you suspect that your soil has too much nitrogen, reduce its level. Alternatively, you can water your plants with cold water, depriving the thrips of the nutrients they need to thrive. You may also consider pruning affected plants regularly to prevent thrips from returning. Another option is to use a mild insecticide such as neem to combat this problem.
If you discover many thrips in your garden, you may want to isolate them for 30 days. You should also isolate any newly planted houseplants for this period. The infestation will likely be less severe during this time than in other garden plants.
Thankfully, thrips have many natural enemies in the environment. Ladybugs, parasitic wasps, and predatory mites are all-natural predators of thrips. You can also take preventative measures by using natural enemies like nematodes. Lastly, you can use a safe pesticide such as rotenone to help control thrips in your garden. While thrips may be able to resist chemical insecticides, you must be aware that these chemicals may kill many beneficial insects that help keep your plants healthy.
You may have a thrips infestation if you notice water spots on your irises. These small insects have rasping mouthparts and feed on leaves and flower petals. When disturbed, they will jump away, so be sure to treat your irises immediately before watering them overhead. The thrips likely are to blame. You can also prevent Iris thrips infestations by treating your plants before they develop.
One common method of destroying thrips in your garden is insecticidal soap. These soaps work by piercing the insect’s shell and destroying its membrane. This dehydrates the insect, suffocates it, and kills it. You can also try using neem oil products. But be aware that they can cause phototoxicity, so they’re best avoided during the active season.
Iris spot
If growing irises in your garden, you must ensure that the soil is well-drained and fertile. You should also avoid planting irises where the soil is saturated during the winter because their roots will rot. Irises should be planted at least one foot deep. You can also use organic matter to improve the soil’s drainage. In addition, a balanced fertilizer can be dug into the planting hole to improve the plant’s overall health.
You may want to consider pruning your iris plants if they are not blooming properly. You can do this by cutting the foliage to about half its original size to improve air circulation around the rhizomes and discourage rhizome rot. When you prune the leaves, cut them at an angle, so rainwater does not pool on the cut surface. You should also remove the foliage once the fall frost kills the leaves. This will reduce the chance of fungal spores overwintering on iris leaves.
Iris leaf spots can be a problem for many irises. The disease causes the leaves to become disfigured and can weaken the plant. The disease is easily identifiable by the yellow and brown spots on the infected leaves. The spots develop gray or black fruiting tufts near the center of the spot. The leaf spot fungus overwinters in the leaves and releases new spores in spring. Fortunately, you can prevent the iris leaf spot by implementing proper cultural practices. You can also use fungicides to control the fungus. One effective fungicide is chlorothalonil. Zineb dust can also be applied to foliage to control the disease.
Irises need light and slightly acidic soil. Japanese Iris, for example, will grow well in a wet environment and flourish in shallow water. Similarly, Professor Fritchie’s Iris, a tall purple perennial, can grow up to five feet tall. Another hardy tetraploid iris is Professor Ike’s, which has full petals. There are also dwarf iris varieties like the Dwarf Crested Iris that thrive in gardens with light shade.
If you have several irises in a single spot, it’s a good idea to divide them. Plant them about eight to 12 inches apart and ensure they face the same way. If you have heavy clay soil, you’ll need to separate the clumps so that the rhizome is above ground level. After three to five years, you can divide them again.
