ISU Winter Days: Conserving, breeding and combining plant varieties

110 perennial gardeners and enthusiasts from 16 countries met in Grünberg from 14-16 February for the 17th time this year to exchange experiences and meet colleagues. Perennials in their natural habitat, in gardens and public green spaces, the selection of perennials and scientific results on the interaction between perennials and insects characterised this year's Winter Days of the ISU International Hardy Plant Union. Gerben Tjeerdsma, ISU board member, moderated the conference, which he organised together with the Bildungsstätte Gartenbau.

Hester Forde from Ireland gave insights into her species-rich and variety-rich garden, which is attractive all year round with perennials and woody plants. Bettina Jaugstetter from Germany showed examples of her designs for traffic islands, urban greening and contributions to garden shows. She chooses drought-tolerant perennials and likes to combine them in mixtures with a wild character. However, the plantings, which are designed to last a long time, require competent maintenance, which the landscape architect also demands. Frederik Persson, Sweden, prefers to design natural landscapes with botanical features and presented impressive projects. Coen Jansen from the Netherlands illustrated that only a very strict selection process leads to new varieties that are successful in the long term, using the colour spectrum of Baptisia seedlings, among other things.

Mike Kintgen, USA, gave a vivid presentation of alpine perennials at several natural sites in North America and in the Denver Botanical Garden. A global ‘Alpine Strategy’ is intended to preserve the plants at the site and as seeds.

Lucie Willan, Greece, reported on the incredibly rich flora in mountainous Greece, which has very different climates. However, the natural beauty spots are under threat from tourism, road building, ski lifts, increasing grazing land and human consumption. Nasim Safari explained that over 8,000 flowering plant species from 132 families can be found in Iran. The Iranian is committed to species protection – over 1,500 species are already on the red list and are threatened by overexploitation, tourism and overgrazing. Noel Kingsbury from the UK explained the influence of the different root developments on plant development and care.

Eric Cederberg from Sweden showed that a great many details have to be taken into account in order to promote insects in gardens. For example, butterflies like to use nettles for oviposition – but different butterfly species are attracted depending on whether the site is sunny or shady.

After the lectures, the participants exchanged information about their respective projects. The ISU Winter Days 2026 will take place from 13-15 February at the Grünberg Centre.