Herbaceous plants hardiness

From previous posts if resistance has mainly woody plants, thus tree, shrubs and half-shrubs. Herbaceous plants have chosen very different strategies than woody plants to survive the cold season. Trees and shrubs have aboveground plant parts must be able to withstand wind and cold without protective cover in order to survive the winter. Most herbs however wilt down in the autumn and it is their so-called wintering buds that will determine what conditions they need to survive. These buds are either well below the earth (such as the bulbs and daylilies) or just at the soil surface (as the dandelion, svartrot eller lungrot). Moreover, there are plants that overwinter in water-saturated soil (as bulrush) or running water (as watercress) [1]. The exception is certain brassicas, having their winter buds surface (in the same manner as kale), which explains why they are so fastidious in its cold parts.

For the perennial vegetables are therefore vintersnötäcket, the moisture content in the soil and frost depth that are most important to their survival. Is there a thick insulating blanket of snow all winter, a plant may be resistant way up in the country, but the fare may be worse in areas where it is often bare ground where overwintering buds are exposed to very low temperatures. In wet places, there are few interesting herbs that thrive while well-drained soil instead increases the survival chances enormously. To take account of these important differences between woody and herbaceous plants have been developed a separate system to indicate the resistance of herbaceous plants. The system has identifiers A to D [2]:

A: Hardy throughout the country, such as ostrich fern and rhubarb.

B: Can be grown throughout the country in protected and well-drained location, for example jätterams, daggfunkia and hablitzia.

C: Can be grown in large parts of the country in protected and well-drained location, for example Blitum Bonus-Henricus, Korogi and asparagus.

D: Can only be grown in the country's favorable parts, for example, watercress.

The plants in categories A and B, originally from roughly the same geographic areas (the cold and temperate parts of the northern hemisphere), but the plants in category B is found in nature in the most favorable growing places in these areas. The plants in category C will mostly from areas with a longer growing season than the Swedish and therefore need to be placed in favorable conditions. In the coldest parts of the country they do not work at all. The plants in the D category have a low frost tolerance, which means that they only handle a few degrees below zero and not for extended periods. They grow mainly because of the country's coastal and thereby mildest parts [1].

In summary, you as a grower affect the herbaceous plants' survival in three ways:

1: Make sure the plant site is well drained. Sensitive plants overwinter better in a sandy soil than in clay soil. If you have clay soil, we recommend that you build raised garden beds and you add large amounts of organic matter to the soil.

2: Insulate soil before winter comes. You can cover the soil with leaves, stalk, spruce or like material to create an insulating blanket. In addition to the root system is protected a little extra, you create even better conditions for soil organisms to continue its important work well into autumn.

3: Create and utilize the favorable microclimate. In warm and sheltered positions the plants easier to hibernate, so if it is very windy where you grow it may be a good idea to create or use any form of live or built shelters. For the most part, it is also a bit warmer near the house walls, stone walls and rocks on Earth

This is an edited excerpt from the book "Perennial vegetables: discover, growing enjoy ", which is now commercially available and can be ordered from both Bokus and Adlibris.

Literature

[1] Eklund, F., The Swedish retardant system for perennials : investigation and suggestions for changes. SLU / Horticulture, 2012. http://stud.epsilon.slu.se/4305/.
[2] Tufvesson, A.G., Hardiness Zones and perenners, Everything in the Garden, 2010. http://www.alltomtradgard.se/artiklar/Zoner-och-perenners-hardighet.