The iris family is a huge one, with approximately 250-300 known species and tens of thousands of cultivars. It’s no wonder then, there’s an iris for every climate, season, garden style, and taste. Among the iris we currently have, cold climate gardeners can count on the likes of the Siberian and Blue Flag Iris. For those lucky enough to live in a Mediterranean climate (Central Otago and Hawke’s Bay comes close!), the Algerian, Florentine, and Bearded irises are favourites. If your region is wet, or you favour water gardens, the elegant Japanese water iris will help you out (be aware its more invasive cousin, the Yellow flag iris – Iris pseudacorus, is a pest plant, so don’t be tempted to grow it!). If your taste is for rock gardens, you can count on Iris reticulata and Iris danfordia, and if you’re a container grower and love a splash of colour on your balcony, the Dutch iris is a reliable friend.
Irises offer colour and beauty in every growing season, and even in winter, most of us can hope to catch a glimpse of Iris unguicularis. Right now, however, there’s one iris grabbing everyone’s attention. It’s a blousy show-stopper that comes in almost every imaginable colour, and simply takes centre stage in parks and gardens, stately homes, suburban borders, and perennial beds. We’re talking, of course, of the bearded iris, Iris germinica (or Iris x germanica). However, for all its popularity, many gardeners experience disappointment and frustration when their own ‘beardies’ (as they are affectionately known), refuse to bloom. If your beardies are refusing to cooperate, we have some tips very likely to solve your problem! What’s more, they’re so easy to put into practise. So let’s take a look at the first aid these beauties may need:
Light and heat are two requirements bearded iris can’t get enough of. Refusing to thrive unless they have at least 6 hours of direct light each day, yours may be failing to bloom because they’re in a spot in your garden that receives less sun than is good for them. Or you may have planted them years ago, before that shrub or hedge grew up to shade the spot. If a lack of sunlight is the problem, don’t worry, because your beardies will be happy to move home any time from mid- to late-summer (or around 5-8 weeks after they finish flowering). Heat is the other must-have for bearded iris – and most importantly, the heat needs to directly contact their rhizomes (the gnarly, woody-looking, thickened stem from which the plants’ roots grow from). If you plant your iris too deep, their rhizomes won’t ‘bake’ in the heat as they need to. In fact, it’s much better to ‘settle’ the rhizomes into the ground rather than bury them, keeping the roots, and no more than the lower two thirds of the rhizome, in the soil, and the gnarly parts exposed!
Bearded iris also perform poorly when they’re forced to jostle for space. To avoid the situation of overcrowding, divide up your clumps of bearded iris every 3 to 5 years by gently prizing them from the bed 5-8 weeks after blooming has finished. Lightly tug the rhizomes apart, and use this division exercise as a time to cut away any rotten rhizome. Before you replant your iris, let them dry in the sun for a few hours so any cuts or nicks heal over. The last step before replanting, is to trim the foliage back by a third.
Apart from disease (if wet, humid conditions persist, rot can set into the rhizomes) bearded iris can be enjoying all the sun they need, have their rhizomes exposed to the heat, be completely uncrowded, and still not bloom as you want them to. If this is the case, it’s almost always because you’re being too generous with water and fertilizer. To rectify the situation, your job is to create a garden for your beardies which replicates, as far as possible, their native home. This is the dry, uncultivated lands of central Europe and the Mediterranean. If you can’t provide this arid environment, do your best by planting into ground offering plenty of excellent drainage (creating a bed with a deep layer of fine, sharp sand can help). Steer clear of nitrogen-rich fertilizer, opting instead for granules that have a 5-5-10 ratio on the packet. Sprinkle this in and around the rhizomes in early spring and after blooming.
Bearded iris aren’t difficult or demanding to grow, but if you don’t provide them with the basics they crave – they’ll soon let you know. Plan ahead for next spring, and pride yourself on having the best ‘beardies’ in the street!