Selecting an iris variety for your garden

Laimonis Zaķis (www.irisgarden.lv)

Bearded irises are a very popular culture in Latvia, and worldwide. According to my estimatse there could be about 1,000 varieties of bearded irises in active cultivation in Latvia, and ten times more in the world.

How can an amateur gardener, landscape gardener or a beginner not be confused by the large choice? I want to share some thoughts and insights that can help in the selection process, perhaps discourage you from buying something blindly, and ultimately help you find the best and most suitable variety for you, your garden, or collection.

Basic principles for choosing 

Giants or dwarfs? Everyone has different taste. There are “giant-lovers” who are attracted only by large, or giant varieties of flowers. Unfortunately, not many people take the changeable weather conditions in Latvia into consideration even though there have been heavy rainfalls and gusts of wind in June for several years in a row, which is when the tall iris blooms. After weather like this it is precisely the giants that can be found “face down in the mud”. The smart gardener will find a place for irises of various heights in their ornamental, or collection garden, but they will choose medium-sized varieties with strong, durable petals and thick, hardy flowers to plant in the open.

Extending the flowering period. If you have carefully tended to a flower culture and come to love it, then you of course want to be able to enjoy the fabulous flowers for as long as possible. If you’ve chosen the right iris variety, they can shine in your garden for up to two months. If it’s a warm spring, the first dwarf irises can flower at the end of April already, followed by other dwarf varieties. Intermediate varieties start to bloom at the end of May, then the tall varieties. The varieties of tall irises that bloom the latest only start flowering around Midsummer, or even later. If someone only grows tall irises, then it is important to choose a mix of both early and very late varieties, so that the irises can bring you joy throughout June.

The strength and vitality of a variety. Since we are in Latvia with harsh, often erratic winters, where thaws can be followed by hard frosts, we are in the risk zone for growing irises. Each collector will have their own horror story about having bought varieties they have long sought for and dearly desired for a lot of money, only to have them perish in the first or second winter. It happens. Sometimes a variety can survive, but the buds might freeze regularly so flowers can only be expected to bloom maybe once every 3 years. This can happen too. Those collectors who order the latest plant varieties from the world’s leading companies suffer the most because those companies are, of course, located in the places most suitable for growing irises like California and Oregon. It takes at least 3 years before you can be sure that the varieties that have survived have acclimatised and will be suitable for Latvian gardens. When choosing a variety, information about its growing potential and how abundantly it will flower is very important! This mainly applies to tall irises, as intermediate and dwarf irises are hardier and thrive better. Locally bred varieties are much hardier as the seedlings have undergone a natural selection process, then been selected, tested and propagated by breeders in the same conditions in which they will continue to grow and bloom. There are, however, currently not so many varieties like this. 

A flower’s ornamental properties are more a matter of individual taste, but often this criterion is decisive in choosing a variety, regardless of all the information above. People decide that they like a certain flower, want it, and don’t want to hear that another one is similar, but will grow better!

Iris culture has come a long way – from varieties we can still find in our grandmothers’ gardens, or in old parks to the fantastic shapes and colors we see today. The 1970s and 1980s were a time when intensive selection work dramatically increased flowers’ size, improved their shape, and they developed ruffles. In the next two decades new colours, colour combinations and patterns, contrasting beards, spots, and edges, mesh patterns on the petals and a wide range of so-called “horned” irises were introduced. Today, any iris lover can find a flower that suits their taste – from bright, clean colours to unusual, even clashing and exotic colour blends.

Where to look for the most comprehensive information about iris varieties?

1. The most comprehensive selection of information, pictures, descriptions, breeder discussions and company catalogues can be found on the Internet;
2. Iris catalogues published in Latvia with descriptions and photographs of different varieties;
3. Iris flower shows;
4. By visiting collection gardens;
5. Descriptions of varieties selected in Latvia can be found in our iris and gladiolus register: https://gladioluunirisuregistrs.weebly.com/

The most useful resource on the Internet would be the American Iris Society (AIS) website. They are the world’s leading association of iris growers and the website provides comprehensive information on award-winning iris varieties, results from annual surveys, links to regional associations and clubs, and links to websites of commercial companies. There is an interesting and promising new project to make an online iris encyclopedia. While it is still in development, it already contains specific information on many varieties, including photographs (http://wiki.irises.org/bin/view).

Information from sources on the internet, especially commercial breeders’ catalogues, should of course be assessed critically. No one will write in their catalogue that a certain variety does not grow, multiply, or gets sick. Even photographs are not always reliable – they can be too small, of poor quality or, quite the opposite, edited to look better –you can, therefore, only get a rough idea of the type of colour, flower shape, or ruffle. You will also not be able find the answer to the biggest question – how a certain variety will fare in Latvian conditions.

Catalogues published in Latvia give an insight into the current varieties on offer and provide short descriptions. Unfortunately, however, due to the limited number of publications and the cost of colour printing, only a small number of varieties have colour photographs available. Currently, the most extensive and serious catalogues are Laimonis un draugi. Īrisi, a joint catalogue of four collectors and breeders where you can find descriptions of about 500 bearded irises from all groups each year, breeder Ilga Vinķele’s iris catalogue and the iris section in the ornamental plant catalogue published by the Hedera garden center.

Iris shows provide an excellent opportunity for anyone who’s interested in getting acquainted with international breeders’ newest, as well as the not-so-new, varieties. You can also evaluate the work of domestic breeders. It’s better to see flowers in real life rather than to read descriptions and exert your imagination. The selection at larger shows can be quite vast, especially at the annual iris flower show at the Latvian Museum of Natural History where at least 200 tall iris varieties are on display. Is it possible to get comprehensive enough information at the show to be able to say with confidence that “this variety is perfect for my garden!”? Doubtful… You can evaluate a flower subjectively at the show, find out your likes and dislikes, be enthralled, or leave indifferent. It’s possible to pass by an amazing variety without noticing it, because its colours look “washed out” in the artificial lighting (this is the disadvantage at almost all shows – irises display their real colours and brilliance only in sunlight, additionally flowers can leave a very different impression depending on the time of day, so seeing a flower in morning, noon or evening sun can reveal many different shades…). We can make a note of a variety in our notebook in capital letters highlighting it as absolutely necessary to buy, persistently search for seedlings for several years, get upset with breeders if we fail to find it all without knowing that this variety is a dud that barely survives in the garden, that it is sickly and does not multiply. So, let’s get back to the important question – is it possible to find out how a variety that we’ve chosen will grow in our own garden at a show? Indirectly yes. If we visit shows regularly and see the varieties that we are interested in often enough, we can notice whether they bloom well for several collectors. This is a sign that there won’t be any problems with this variety. Usually it is flowers from sufficiently propagated varieties are brought to shows. The show’s consultant can also usually help within the limits of their expertise regarding different varieties’ characteristics.

What is it that we don’t see? At a show we cannot get an overview of what an iris cluster will look like, how abundantly it might flower, how healthy a variety is or its ability to multiply. These are things which we can only see and appreciate in nature.

Collection gardens. There are several popular flower culture gardens in Latvia for other varieties of flowers like daylilies, or dahlias. An iris collection garden that is open to visitors would provide a great opportunity for people to see and be able to objectively evaluate different iris varieties in their natural environment. This is the only way in which you can see and understand what is more valuable and useful – the tall lone flower you noticed at an exhibition, or perhaps a cluster of intermediate irises covered in flowers. Seeing the colours dazzle in the sunlight, experiencing a cloud of scent wafting across a garden, comparing similar, but different green sword-like leaves, seeing a local variety’s abundant cluster next to a scraggy guest from California – this is the kind of information that cannot be conveyed by a photograph, or captured by a few meagre lines in a catalogue. The largest iris growers and breeders in the USA and Europe have specific times that visitors can come during flowering season, allowing them to take a walk, appraise and take photos, but usually only in a special part of the gardens, not where the flowers are grown for production.

Here’s hoping that one day there will be fantastic irises in every garden, that their beauty will keep gloomy thoughts at bay and help us overcome our problems.

WHAT NEEDS TO BE TAKEN INTO CONSIDERATION IN ORDER FOR BEARDED IRISES TO GROW, FLOWER AND OVERWINTER IN LATVIAN CONDITIONS?

1. Plant irises in a sunny location, in loose and permeable soil.
2. Bearded irises do not love moisture. Excessive moisture, even temporary flooding when the snow melts, can prove fatal, so it’s best to choose an elevated or sloped area for planting. Don’t get carried away with watering your irises! Young plants can, however, be watered during the rooting period.
3. The best soil for growing irises should be neutral, or even slightly alkaline. Irises consume calcium from the soil, so it is recommended that calcium be added before planting and to use a fertiliser that does not acidify the soil. Irises like reasonable amounts of ash.
4. Don’t get carried away with excessive fertilisation. Never use a fertiliser with high nitrogen content after flowering. This could make it harder for the irises to survive the winter, or cause an increase in green leaves, but result in poor flowering the subsequent year!
5. Irises should be replanted when the clusters have become denser and hollow in the middle, and when there are fewer flowers. Usually tall irises can grow in one place for 3 to 4 years, but this also depends on how they multiply.
6. The best time for replanting is in July, because then the iris seedlings have matured and are still able to take root before the frost. Tall irises can, however, be replanted even during flowering, because then the new roots, which are just beginning to form, are less likely to be damaged.
7. Irises should be planted shallow so that the surface of the rhizome is visible. In excessively hot and dry summers, they can be covered up with slightly more soil during the rooting period.
8. It is recommended that irises be covered in order for them to overwinter well. This is especially true for new plants and new varieties that are not totally suitable to Latvian conditions. Do not use peat! Do not use materials that absorb and retain moisture for a long time, or that become very compact. Rhizomes can be covered with soil, sand, or spruce branches in the autumn. Irises are more affected by repeated cycles of thaw and frost, especially in the spring, than by the cold.
9. Do not forget to regularly inspect your irises throughout the summer, even after they have flowered, in order to be able to catch bacterial rot that can cause iris rhizomes to turn into a smelly mass. This can be particularly devastating in thicker clusters during warm and humid summers. Make sure you cut back the rhizome to all white healthy tissue!
10. In order not to lose the plants’ beauty at the end of the summer, it is best to spray the leaves with a fungicide so they don’t become mottled.

The basic requirements for cultivation are similar for all bearded irises, but tall irises require the most attention. Intermediate and especially dwarf varieties are more suitable to Latvian conditions, they overwinter better and practically don’t get sick.

Replanting irises

For an experienced iris collector it is commonplace to transplant irises annually. A collection garden is constantly changing – new beds are created every year, spare varieties of the most valuable species are left, the feeblest plants are rescued and replanted, and the thickest clusters are divided. It’s a neverending process that requires a lot of tools.

For beginners, or people with decorative gardens, for whom a couple of iris clusters would just be an addition to the many other plants and flowers they have, holding a few newly purchased seedlings in their hand for the first time, or looking at their overgrown clusters can raise a number of questions. When should they be replanted? How should they be divided? What location to choose? Will the dried-out seedling I just bought and that has almost no roots even grow? I will try to answer some of the main questions.

Timeline for replanting bearded irises

The best time for replanting irises in Latvian conditions is from the time they begin to flower until the end of July, or the beginning of August at the latest. Both replanting early and late has its advantages. If we divide an iris during, or immediately after flowering we see that the old roots are beginning to die off, but that new, white roots are taking shape in the new part of the rhizome that has grown that year. Sometimes only small, yellow bumps are visible. Once in the soil, a plant like this takes root quickly. The new roots are not damaged, and they are less affected by the stress of replanting. True, the seedling will be smaller in the early replanting period because the new root has not yet accumulated sufficient reserves, but it will have a much longer rooting and growing period until the end of the growing season, which increases the chances of the iris blooming the subsequent year. However, plant traders often have to listen to accusations that the plants are too small, the roots too frail, therefore in order to indulge buyers’ demands, we leave large pieces of the old rhizome with dying roots on the young plant.

By planting irises at the end of July the seedlings will have matured well, they will have strong leaves and root systems, and the the new rhizome may have already developed dormant buds that will give off side shoots already in the autumn, or the following spring. As the flower buds for the following year’s tall irises usually take shape in August in Latvian conditions, when the plant’s shoot has reached its “critical mass” (i.e has a firm fan of leaves, with at least 6-7 leaves), the possibility that the replanted iris will bloom the following year depends on how successfully it has taken root in the new location, and whether the weather conditions during this period are favourable. The characteristics of the specific variety can also be decisive.

It is not recommended to replant in early spring or late autumn. If you are interested in experimenting, it is better to do so with an old variety. In early spring a replanted plant’s life cycle has been disrupted and will usually only recover after a year. The plants that have been planted in the autumn do not manage to take root properly, and they can be lifted up during our inconsistent winters, or the roots can tear with sad consequences. If your circumstances make you have to dig your irises up in the autumn, it is better to dry the seedlings out and store them in a cool room until spring. I have tested this in practice, and they survived better this way (and even had flowers!) than they would have if I had planted them late.

Choosing a location and soil

The basic growing requirements for all bearded irises are similar: the dwarf and intermediate varieties are better at adapting to adverse conditions, the taller varieties will have to be looked after a little more carefully.

Location – definitely a warm and sunny garden. Irises will feel great by a south-facing wall, or by a wall that reflects the heat from the sun. They can also be planted in the open, but partial shade between bushes, or in a crowded flower bed with other plants is definitely not desirable. Excessive moisture, or dew that dries slowly can contribute to blemishes on the leaves, or even root rot. While it’s true that bearded irises can grow in partial shade, it would be naïve to hope for abundant flowering. If the chosen location is lower down, it is advisable to find a small hill or slope so that excess water can drain. Even a brief flooding can be detrimental for irises.

Choose loose, permeable soil that is neutral or slightly alkaline. More acidic soil should be limed by using dolomite flour, or garden lime, preferably both in approximately equal doses to ensure the best ratio of calcium to magnesium. You shouldn’t get carried away with preparing your soil, and especially with fertilisation as bearded irises will grow well in any garden soil and by trying too hard to improve it, we can cause more harm than good. In my personal opinion organic fertilisers (like compost, peat, and black earth) are better kept far away from irises. My worst experience with bacterial rot was when the irises grew in just such fertile soil, rich with organic matter. It is also better to refrain from nitrogen or complex fertilisers with a high nitrogen content. Irises will feel great in regular garden soil, and can even grow for several years without any additional fertilisation. If the plants form large, dark green leaves, but aren’t even considering flowering, one of the reasons will probably be over-fertilisation.

If the soil is heavy and clayey, I recommend mixing in coarse sand or sifted gravel. You can also do this topically at the site where you plant the iris if you’re only planning on growing a few clusters. It can be beneficial to add a bit of clayey earth to light, sandy soil.

Iris seedlings – preparation and planting

An iris seedling is a fan of leaves shortened to approximately 15cm, a piece of rhizome with roots, which are also shortened in proportion to the top of the leaves. Do the following: take the roots in your hand together with the rhizome and cut off the excess that hangs out. If you plant early, before new roots have formed, it is better to prune the leaves even shorter. In this case, the old roots can be used to fix the plant in the soil, but they have no other practical value. If you have to deal with only a few dense clusters in your garden, you don’t necessarily have to to dig them out completely. You can even separate out every second root with a knife, lift them up with a garden fork, and pull the severed parts of the cluster out of the ground. Stomp the soil you have shifted down around the cluster, and prepare the plants you get as mentioned above, and plant in them in a new location.

My colleagues and I joke that a good iris plant can be dropped onto the ground, stomped on, and still grow. This is actually kind of true, as bearded irises require shallow planting – the surface of the rhizome must be visible at the level of the soil. Create a hole for the roots in the place you’ve chosen for planting and make a little mound in the middle. Place the plant on top of it and, if you’re a perfectionist, arrange the roots evenly, gather the soil and compact it tightly. You can water it in dry weather. More watering would be unnecessary, as irises survive with minimal moisture in the soil. If the new roots are still short, the plant should be reinforced. This can be done by attaching the rhizome to the soil with a wooden peg, a bent wire, or by tying the plant to a stake inserted at the back – whichever method you find more convenient.

The distance depends on the type and purpose of the planting. It should be taken into account that for a normal plantation, that you are expecting to replant after 3-4 years, it would not be advisable to plant more than 4 tall irises per square metre. If you want your plants to flower sooner, you can plant them closer and not divide the seedlings one by one, but in this case each group should be made up of one variety.

A few final questions…

Do irises need to be covered in the winter? New plants should be covered, including varieties with low winter hardiness. When the frost comes you can sprinkle sand on the visible rhizomes, cover clusters with spruce branches, and if there is risk of extreme frost you can supplement the covering with dry leaves. You shouldn’t use dense, moisture-absorbent coverings. In the spring, all excess covering must be removed sooner rather than later as irises that have been uncovered too late will be more affected by frost.

Should iris leaves be trimmed after flowering? Definitely not! After the iris flowers wilt, it is recommended that you break the stalks down to the rhizome as they can begin to rot. The surface of the leaves should be kept as large as possible as that is where nutrients for the root and the flower buds are produced. If spots appear on the leaves, it is recommended that they be sprayed with a fungicide.