There is no doubt that one key reason why the bearded irises have remained popular for several centuries is the fact that these plants possess the aptitude to survive as well as flourish in various different environmental circumstances. While the perfect soil for growing these iris varieties is one that is almost neutral, having a pH of 6.8, these plants can grow somewhat successful even in soils whose pH ranges between 6.0 and 8.0 (from gently acidic to slightly alkaline). It is worth mentioning here that when we say that the soil is neutral, it means its pH is 7.0. Anything above this is considered to be alkaline or basic, while a pH below 7.0 is acidic.
If the soil in your garden has a pH of less than 6.0 and is somewhat acidic, it is advisable that you blend some lime with the soil as per the instructions on the product container. If you want to increase the pH of the soil from 5.0 to 6.5 you will be requiring to take anything between 8 pounds and 15 pounds of lime for each 100 square feet of soil, subject to the type of soil. You need less lime for sandy loam compared to the clay loam. On the other hand, if the soil in your garden is excessively alkaline having a pH of more than 8.0, you can bring down the pH by blending the soil with aluminium sulfate, soil sulfur or ferrous sulfate. You will be requiring about 2 pounds of these substances for every 100 square feet of soil. Allow the mixture to settle and examine the soil again after two weeks. If required, repeat the process.
To ensure that your irises produce best blooms every year, you need to have a site having soil of average fertility and receiving enough sunlight. Bearded irises require no less than half day's sunlight. The plants are at their best performance when they are grown in full sunlight. When bearded irises are grown in too hot climates, it would be beneficial for the plants if they are provided with some shade later in the day. It has been found that the bearded irises usually do not thrive when grown in the hot and humid climatic conditions prevailing in Florida, a southern state of the United States, as well as the Gulf Coast, where it rains during summer, which is usually warm. On the other hand, bearded irises flourish when grown in the arid areas of the southern United States.
While bearded irises usually thrive well in an assortment of soil types, they generally perform to their utmost potential when grown in soils that are classified either as clay loam or just loam. One of the major conditions necessary for growing bearded irises, and growing them well, is a soil with an excellent drainage. In case, the soil in your garden lacks these attributes, you will have to amend the soil by mixing organic substances to ensure that bearded irises thrive well. In order to enhance the structure of extremely clay or sandy soils and make them fit for growing bearded irises, it is essential to cultivate about 3 inches to 4 inches of properly decomposed manure, compost or superior quality peat moss into the soil in your garden to a depth of anything between 12 inches and 15 inches about two or three weeks prior to planting the bearded irises.
It is not advisable to plant bearded irises on slopes where rains are likely to accumulate silt and soil against their rhizomes and sometimes also cover the rhizomes. Iris rhizomes will be in their best health when they are completely exposed to air and sun. A number of experts suggest that when irises are grown in extremely cold climatic conditions their rhizomes should be lightly covered with soil. On the other hand, others are of the view that the rhizomes should be left uncovered and exposed to air and sun under all circumstances - irrespective of how harsh the winters are.
Contrary to cold winters, regions where the temperatures vary between 20�F and 70�F within a span of just 24 hours may actually prove to be hard for irises. While most iris varieties lie dormant during the winter months, a few irises actually do not become completely dormant or get into a dormant phase at all during winters. You can grow this type of irises successfully in places having mild climatic conditions. However, these types of irises will probably get lost when grown in climatic conditions with severe freeze-thaw phases. If the winters are snowless in your region, you can protect your favourite bearded irises by providing them with somewhat light mulch comprising loose straw.
When you understand the growth patterns of bearded irises you will know why growers in cooler climates prefer to undertake planting of this iris variety during the period between July and August, while those in warmer climates chose to plant them during the later part of the fall. Most of the over ground growth of bearded irises occurs during the period between the beginning of spring and the time when the blooms just begin to appear. The nutrients and moisture stored in the plants' rhizomes are used to support the growth of the leaves, flowering spikes and flowers. For about six to eight weeks after the flowering season of bearded irises is over, the growth of the plants mainly occurs under the ground. At the same time, the growth of bearded irises during this period also concentrates on developing more buds that will eventually form new rhizomes and developing new flowering stalk buds that will produce the blooms in the subsequent year's growing season. Simultaneously with their underground growth, the plants also keep storing up nutrients and moisture that would be used to support their growth in the following year.
By the time the underground growth of bearded iris concludes, the plants become mature and go into a partial dormancy period. However, there are some bearded iris varieties that rebloom and continue growing all through the warm season. In fact, this is the ideal time to transplant the bearded irises, as their rhizomes become fully developed during this period. Moreover, the plants are also in a semi-dormant condition in late summer, which means they would not be disturbed if transplanted during this period.
If you undertake transplanting during this period, it will help the rhizomes to set off growing new roots in a moist soil till the time when the first frost of the season is expected in your region. In fact, it is vital to provide the roots of the newly planted irises with an opportunity to establish them properly prior to their growing season come to an end. After dividing the rhizomes and prior to transplanting them, it is important to allow the rhizomes enough time to dry thoroughly for a number of days, may be even a week, as it will help to dry as well as callus the incised surfaces and reduce the risks of developing any fungal disease. Alternatively, you may also dust the cut surfaces lightly with horticultural sulfur with a view to deter fungal infections.
Make a broad, not too deep, planting hole retaining a soil mound in its center. Place the rhizome on the soil mound and carefully spread the roots of the rhizome all around it. Position the rhizome in such a manner that its leaf fans face the external edge of the iris bed to make sure that the potential growth does not result in a packed group of rhizomes. Subsequently, fill the hole with the dug up soil ensuring that the rhizome lies at the same level of the soil surface and a little exposed to air and sunlight. If the soil in your garden is very light and the climate is extremely hot in your region, experts suggest that you should cover the rhizomes with a thin soil layer - about an inch thick. After planting the rhizome, water it properly and subsequently water the rhizome on a regular basis, especially if the soil is arid.
Garden irises require some general care, which includes dividing or thinning the plants once in three to five years, subject to the extent to which they have become crowded. If you notice any foliage that is injured or damaged, trim it carefully. At the same time, you need to ensure that you do not disturb the healthy verdant foliage in any way. You should also make sure that the iris bed is free from debris and all types of weeds to allow the upper surface of the rhizome to receive enough sunlight during the summer. When the flowering season is over, snap or cut down the flowering stems almost to the ground level. A number of iris growers apply an inch thick pine needle layer to mulch the plants with a view to put off weeding. However, while mulching the plants, be careful not to cover or even touch the rhizome.