Nearly all plants can be propagated by two main means - sexually and asexually. When the plants are propagated sexually, the progeny has a mixed genetic material, with each of the parents contributing one half. This is the precise way by which new cultivars of irises are developed. Sexual propagation offers a number of advantages, including the fact that it enables the breeders to develop fresh genetic uniqueness that may result in new flower patterns, new colors, enhanced beauty, new forms, augmented resistance to diseases as well as several other attributes. During sexual reproduction, a breeder crosses the two preferred parent plants artificially, and subsequently grows the resultant seeds. In addition to this process, open pollination is another means of sexual reproduction of plants. Open pollination is also known as bee pollination or open breeding, wherein the sexual crosses occur in nature with assistance from the bees or other pollinating insects devoid of any intervention by the plant breeders. There are various ways by which plants can be propagated asexually - such as cuttings, divisions and layerings. Cuttings may involve the plant's leaves, stems, roots or even leaf parts. In recent times, tissue culture has been included in the asexual propagation of plants, but most gardeners do not practice this method, which involves an extremely technical laboratory method. In tissue culture, scientists take identical tissues - for instance, those found in the growing tips, root tips and plant embryos, and culture them in a specially prepared media in a manner that the ensuing cell mass produces minuscule new plants. In fact, all such new plants are clones. In other words, genetically they are identical to the plants whose parts were used in the tissue culture. Like sexual reproduction of plants, asexual propagation too offers some distinct advantages. In other words, it enables the breeders to duplicate plants genetically. While new cultivars of irises are developed by means of sexual propagation, asexual reproduction helps to replicate the plants enabling several gardeners to enjoy the benefits of the latest creations. As far as irises are concerned, root division is the most important as well as common means to reproduce plants asexually. When plants are divided by means of division, gardeners can obtain clones of the parent or original plants. What is important in this case is that the progenies are genetically same in every manner as their parents or common ancestors. However, there may be certain differences, but this is mainly owing to the care these plants have received in the gardens. Asexual propagation of plants is necessary if you desire to have dependable plants having all the characteristics of their parents or ancestors that have a particular cultivar names. Therefore, plants of a particular cultivar should essentially be clones of each other and also precisely possess identical genetic identities when they are propagated asexually.
If you are growing bearded irises, which are rhizomatous, it is essential to divide the plants once in three to four years, as this will help to perform at their optimal level. Gardeners in some places divide the bearded irises more frequently. Once these plants have grown in the same place of your garden for over three years, they are likely to be congested and, as a result, produce smaller number of flowers. Even the rhizomes of bearded irises expand and, in due course, become meshed in a dense mass that forms a cover over the iris bed. Some bearded iris varieties are more dynamic and these may require being divided even more frequently. While it is feasible to dig up the ground and divide the rhizomes of bearded irises anytime when you are working on the plants, in most regions in the United States, they should ideally be transplanted when the rhizomes have attained their utmost growth and lying in a partially dormant state during the period between July and the beginning of September. The main idea is to divide the bearded iris rhizomes and replant them at the appropriate time with a view to allow them enough time to grow new roots all through the fall and essentially before the arrival of winter. In case you undertake the division of bearded irises during spring, it will possibly not affect the growth of the new plants, but they will probably not bloom in the same year. In this way, you may have to forgo the flowers of the current year. On the other hand, dividing as well as transplanting the bearded irises very late into the fall will not give the plants sufficient time to grow new roots and establish them again in the garden. As a result, the plants will wither away during the cold winter due to the freeze-thaw cycles. Therefore, it is important to be familiar with the bearded irises' growing cycles, as it will help you to choose the right time to undertake divisions and transplanting them. Irises start growing above the ground as the soil begins to warm up in spring. It is during this time of the year that the plants develop new foliage, buds as well as flowers. At the same time, the roots on the rhizomes of the previous year begin to decay and eventually disappear during the spring. On the other hand, the new roots of irises start growing on the current year's prolific rhizomes and they take up the job of providing water and nutrients to the new foliage. When the plants are in bloom, the rhizome as well the roots continue to grow for about another two months on flourishing rhizomes of the current year. Throughout this period, the plants continue storing nutrients in their rhizomes for use during their growth in the subsequent season. This is the time when the rhizomes also develop fresh rhizomatous budding ends, which will give rise to foliage fans as well as flower buds in the following year. The shape of the rhizomes' developing reproductive parts has a resemblance to the English alphabet Y. While the leg or the base of this Y is the rhizome's older part, while the arms of the Y are the new parts. The growth of the subsequent year will occur at these new parts of the rhizome. When the growing period of the bearded irises has ended, nearly all plants take a break till the arrival of the rains in late summer. In fact, the irises remain in a partially dormant state during this period. However, there are exceptions to this rule and the reblooming irises are an excellent example of this. The growth of this iris variety is incessant all through the summer and, hence, they need to collect moisture as well as nutrients all the time for producing recurring stalks, buds as well as flowers. The arrival of the rains in late summer coupled with a somewhat cooler climatic condition sets off a fresh growth of roots. Providing these plants with more water during the hot and arid summer months will facilitate these irises to start their root growth later in the season even earlier. The time period between the plant's growth during the spring and their root growth during late summer is ideal for undertaking the division and transplantation of the bearded irises. In fact, this period allows you to work in a laid-back manner to dig up the irises, cut back the rhizomes and replant them in your garden, as it will be beneficial for the rhizomes to dehydrate for some days. It will be best if the rhizomes are spread out on newspapers and placed in an arid and shaded place for a number of days with a view to help them dry out to some extent. As the rhizomes become dry you will notice a cork-like, tainted surface developing at places where the rhizome is soft or has cuts. In scientific terms, this process is known as callusing. While you dig out the clumps of different iris varieties, ensure that you keep them apart properly as per their particular species or cultivars. Some gardeners find it convenient to keep the dug up clumps of different bearded irises on different newspapers along with their labels collected from their garden beds. Keep the rhizomes separately and check them thoroughly. In some cases, it may be necessary to break or cut the rhizomes. Get rid of the diseased and soft parts of the rhizome using a razor-sharp knife. It is important to clean the knife following each cut, as it will help in checking the disease from spreading to other rhizomes. You can achieve this by wiping the blade carefully and subsequently dipping it in a bottle containing a domestic chlorine solution for some seconds. After you have dug out the rhizome, trim the foliage fans so that their length from the rhizome is anything between 6 inches to 8 inches. When you do this, it will help you to handle as well as replant the foliage fans without any difficulty. It is also important to cut back the smaller variety of bearded irises appropriately. Having completed this task, use a dark indelible marker to write the name of the species or cultivar on the leaves left behind. This will help you to identify the new plants when you are making fresh garden labels. Spruce up the divisions and when you do this, ensure that all the leaf fans have a small, healthy piece of rhizome accompanied by vigorous feeder roots. A number of gardeners prefer making divisions in the shape of Y, as this helps them to have two leaf fans in each division - one each on the minor arms of Y, having a common leg. While replanting the divisions, you should ensure that the rhizomes' growing ends should never face one another. The growing ends should be faced outwardly to prevent the plants from becoming overcrowded very quickly. Once you have made the divisions, trimmed them and marked them writing the name of their species or cultivars, ensure that you allow them to dehydrate and callus in the sunlight for some days. When you do the divisions you do not require immersing them into any fungicide or in any other rooting or drying substance. Prior to transplanting the divisions of bearded irises, it is essential to prepare the beds properly. In addition, you also need to modify the soil by adding compost, properly decomposed cow manure or any other similar substance. Make sure that the soil in the beds is prepared up to a depth of no less than one foot (12 inches). It is advisable that the soil be prepared to an even greater depth if the soil in your garden is not very fertile. While the rhizomes of irises like to sit only a few inches below the top soil, the feeder roots of bearded irises travel further deep. Bearded irises can usually endure soils that vary from sandy loam (concentration of sand, silt and clay) to heavy clay (soil comprising over 50 percent clay). These irises also thrive in soils having a wide pH level, ranging from somewhat acidic to somewhat alkaline. When you are replanting the divisions of irises, you should just cover the top portion of the rhizomes with a layer of roughly half an inch of soil. If the rhizome pieces are small, they will require even less covering. The rhizomes are likely to get sunscald if they are not properly covered with soil. It is important to note that if you plant the iris rhizomes very deep into the ground, they are likely to be susceptible to fungal diseases, particularly root rots. However, when the new plants establish themselves well in the garden, they will grow up to their preferred levels. It is essential to make the planting hole quite large, as this will enable the spreading feeder roots to freely grow outward and down. After transplanting the divisions, press the soil around the rhizomes and roots gently with a view to make it firm. Subsequently, water the divisions appropriately. You can plant the smaller dwarf iris varieties at a distance of just 5 inches or 6 inches from each other with a view to provide a pleasant effect immediately. On the other hand, it is best to plant the tall bearded and larger intermediate iris varieties at intervals of anything between 12 inches (30 cm) and 18 inches (45 cm) with a view to provide them adequate space for growth. If you have a preference for an iris bed that appears to be settled faster, you may plant the relatively big rhizomes close to each other. However, when you do this, you will also require dividing the rhizomes earlier. You ought to bear in mind that positioning the budding ends of the rhizomes in a manner that they are directed away from the clump's center; the irises are unlikely to become crowded very quickly. Nearly all the bearded iris varieties usually produce their best flowers in the first year after dividing them. In fact, the best blooms are produced during second, third as well as fourth years of the division and transplanting. When a plant has been growing in the same position for about five years or even more, the clumps start getting overcrowded at their centers, making the rhizomes at the center less productive over the years. In addition, the plants too do not have as much of foliage.
The ideal time for undertaking vegetative propagation of Siberian irises is the period between the later half of August and through September (late summer to the beginning of fall). On the other hand, if you divide and transplant Siberian irises soon after their flowering season or during the beginning of spring the rate of success will not be very satisfactory. The Siberian irises and Japanese irises are treated in the same manner while dividing their clumps. Usually it is very difficult to divide the clumps of Siberian irises that are well established for a long period, because they have already developed a clutter of roots by then. Therefore, it is important to note down the date when you divide Siberian irises and accordingly make plans to divide them once more after a period of three to four years. It is possible that you will have to use two garden forks in the form of levers to separate the thickets of Siberian irises slim rhizomes and roots in the manner that is adopted to pull apart daylilies. Position the garden forks into the thickset in a way that they face away from one another and, subsequently, force open the clumps by prying the handles of the forks apart. The resultant leverage will help to slacken off the root clump of the Siberian iris. While dividing the Siberian iris clumps, ensure that all the new divisions have around six slender rhizomes each. It is not advisable to make Siberian iris clump divisions each having less than three slender rhizomes, because doing so will make you wait for a prolonged period for the divisions to have the clumpy appearance that is valued much by people who love Siberian irises. When grown in garden beds, solitary rhizomes appear very sparse and, hence, from the aesthetic point of view, you will be happier if you plant several single rhizomes of the identical variety collectively. Once you have dug up the Siberian iris clumps, trim the foliage to roughly 4 inches or 6 inches to ensure that the top growth is least, even as the roots continue to grow and become established. Divisions of Siberian iris along with their rhizomes should always be replanted about 2 inches deep. At the same time, ensure that the divisions are positioned at least 12 inches (30 cm) to 18 inches (45 cm) apart from one another providing them with enough space for growth. Also take care that the planting hole has sufficient space for the elongated fibrous feeder roots of the new plants to spread out comfortably. Ideally, the Siberian iris divisions should be planted in a fertile and damp soil whose pH is slightly acidic, roughly 6.0 or somewhat less. It has been found that the different cultivars of Siberian irises have different levels of endurance for arid conditions. Therefore, when you are purchasing the plants you need to ask for the specific care required by them. In addition, you need to monitor the plants carefully in your garden. Excellent drainage and a constant level of moisture is necessary for the success of Siberian irises in your garden, especially all through their growing season. In the absence of adequate rains during the plants' growing season, it will be essential to water them properly every time the moisture level in the soil is depleted.
Root division of this variety of irises should only be undertaken when you notice new root growths whose length is about 2 inches or even more. Unlike various other irises species, division of Pacific Coast irises should be undertaken subject to the climatic conditions in your region. Sometimes the root divisions of this iris variety is undertaken in the beginning of spring, while it may also be done either during the fall or in winter, subject to the climate in your area. If the climatic condition in your area is mild, you may undertake root division of the Pacific Coast irises anytime during the period between the later part of fall and the beginning of winter to enable the roots to set off growth. Prior to undertaking root division of Pacific Coast irises, you should essentially examine the plant's base thoroughly with your hands or gently using a trowel to find if new white roots have emerged. If they have, it is a sign that the time is appropriate to lift the plant, divide the roots and transplant them. Rinse the roots carefully to remove the soil and subsequently segregate the clumps into a number of fans. It is advisable that you cut back the foliage of the plants by about half, as it will make it easier to handle the plants. Ensure that each division possesses at least one or extra fresh roots. Next, plant the root divisions in pots and provide them with requisite support till further new growth is visible. Plant them outdoors in the garden when sufficient new roots have emerged. It is necessary to plant the divisions in very fertile and somewhat acidic soils. If you have a preference for the Cal-Sibe irises, which are actually cross breeds of irises native to the Pacific Coast and the Siberian irises, you can undertake their root division and transplanting anytime between spring and the start of fall. However, the success rate will possibly be greater if you undertake their division in the period between late summer and the beginning of the fall.
It is necessary to divide as well as replant the Louisiana irises, a tall growing variety, once in three years, provided you want the plants to perform at the optimum level. Ideally, the division process should be undertaken during the period between the later part of summer and middle of fall - precisely speaking between August and October. Dividing the clumps during this time of the year will provide the new plants with enough time to get established before the arrival of winter. This particular iris variety has a rapid growth and also becomes crowded very fast. If the growing conditions are good, different iris varieties can often grow into one another creating a tangled disarray of their rhizomes much faster than one can imagine. Louisiana irises are basically water-loving plants that thrive best when grown in a bog garden. Hence, lifting as well as dividing the plants from their extremely organic, soggy soil is quite a chaotic job. Use a garden fork to excavate the Louisiana clump and subsequently rinse the roots to get rid of the soil - doing so will make it much easier to separate them. Take time to check the rhizomes cautiously and get rid of any part that may be diseased or dead. After you make the divisions, plant them again ensuring that each fan of the divisions possesses some healthy new roots. While replanting the rhizome, ensure that the depth is same as they were in before, because the foliage of this variety of irises may possibly grow up to a height of 2 feet to 4 feet. In addition, you should cover the re-planted rhizomes with a layer of about 1 inch to 1 1/2 inches of soil. While re-planting the rhizomes, make sure that its growing end is positioned upward in the planting site, as this will reduce crowding. Preferably, you should leave a space of about 1 1/2 feet between two Louisiana iris plants, as this will prevent them from invading each other's area. Louisiana irises will grow best when planted in an acidic soil that is always moist and is rich in organic substances.
It is quite easy to divide spuria irises. However, sometimes it may take about two years for the young plants to get established and flower again. In fact, growing this beardless iris variety in moisture retentive soils will facilitate the plants to grow and bloom quickly. Provided you are fertilizing the spuria iris clumps, which often grow up to a height of anything between 5 feet and 6 feet, on a regular basis, you may well leave them to grow in the same place for more than a decade. Dig out the spuria iris clump and take the rhizomes and roots apart. Check the rhizome carefully to see if there is any diseased or dead part. Also see if the rhizome has any part that is not quite vigorous. Cut back the foliage to about 6 inches or even less and use an indelible marker to note the variety on a leaf to enable you to make a label after you have planted the division. Alternatively, you may also write down the name of the variety on your personal garden plan specifying the precise place where the new divisions are positioned. Next, plant the rhizomes in the depth that they were in before. Ensure that the soil is very rich and its pH level is between neutral and somewhat alkaline (7.0 or a little higher). After replanting, cover the rhizomes with roughly one inch of soil.
Japanese irises should essentially be divided once in three years. The ideal time to divide and replant this beautiful iris variety is the same as other irises - during the period between the later part of summer and beginning of fall. Dividing the older Japanese iris clumps during this part of the year provides enough time for the new divisions to establish themselves and start developing new roots prior to the arrival of winter. It is important to note that dividing the clumps of Japanese iris during spring is not advisable. If you undertake the process in spring, there is a likelihood that a number of new divisions will die, while some other divisions may not bear flowers in the subsequent season. In order to handle the plants better, first you need to reduce their foliage by roughly five inches. Next, excavate the whole clump and pry as well as lever apart the compact, rhizomatous root of the plant using two garden forks. Divide the original clump into a number of large masses. Ensure that the new divisions to be planted in the garden beds have no less than three fans. However, a solitary fan will also do, as it will increase rapidly to fill in the numbers. Plant the new root divisions roughly three inches deep into very fertile and vastly organic soil having a pH of approximately 5.5 (an acidic soil). Ensure that the rhizomes of the Japanese iris do not dry off when you are in the process of dividing as well as transplanting the divisions.
To propagate bulbous irises vegetatively, you first need to excavate the plants when they are lying dormant - anytime following the flowering season and when the foliage has matured and become yellowish. Take the small offshoots apart from the old bulbs and throw away the latter. Plant the young offshoots individually. While you are handling the bulbs, be careful not to scratch or cut them. Subject to the species, it is best to plant these new iris offshoots about four inches deep in sandy loam. The relatively large bulbs should be planted six inches deep, which is about thrice the bulb's height. These iris plants need almost the same culture that is required by daffodils or tulips.
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