Judas tree: planting, pruning & overwintering

Already in April and May, even before they bear foliage, Judas trees unfold their flowering splendour. Read on to find out where the trees come from and how to care for them properly.

Judas or redbud trees are colourful plants for the home garden not only because of their beautiful flowers, but also because of their special autumn colour. We explain what distinguishes the butterfly plant, what species and varieties there are and what to consider when planting.

Judas tree: leaves, flower and characteristics

Judas trees (Cercis) or redbud trees bring a special flowering splendour to the garden. In fact, the plant genus forms its flowers on old parts of the trunk and not on young wood, as is the case with most flowering trees and shrubs. Redbud trees have different names according to the region and are referred to as Judas trees or European redbuds, among others. The Redbud tree genus belongs to the Leguminosae or Fabaceae family. The species most commonly planted in our area, the common Judas tree (Cercis siliquastrum), originates from the southern European and Near Eastern Mediterranean regions. This supports the legend behind its name but is grim: after Judas Iscariot betrayed Jesus to the Romans, he hanged himself from one of the trees, whereupon the tree turned red from shame. Other species from North America and Central Asia are also widespread in our country today.

Judas trees grow as deciduous shrubs or multi-stemmed trees that can usually reach between 4 and 8 feet tall, although dwarf forms also exist. Because of the deep-reaching main root and weakly developed fine and lateral roots, planting Redbud tree in a container is possible only for young plants. The bark has an olive-brown to black-brown colouration and is usually cracked, furrowed or scaled. The alternate, heart- or kidney-shaped leaves, which have a thin leaf blade, are striking.

Even before the leaves shoot, the Judas tree comes into bloom from April to May. The short, racemose flowerheads consist of up to ten individual flowers that are conspicuous for their five reddish to purplish, bell-shaped fused sepals. More discreet are the five purple to pink petals and the ten uniform anthers. Naturally, the Judas tree is pollinated by insects such as bees. Up to 10 cm long, banana-shaped legumes are formed from the flowers, which contain a large number of small, egg-shaped seeds and are dispersed by the wind due to their light weight.

The most beautiful species and varieties of Judas tree

There are three species of Judas tree used for horticultural purposes: the common Judas tree (Cercis siliquastrum), also called the European Redbud tree, the American or Canadian Judas tree (C. canadensis), and the Chinese Judas tree (C. chinensis). The leaves of the common and Chinese Judas tree have a bronze hue where the leaves emerge, during vegetation they are green and finally acquire the familiar Judas tree autumn colouration in vivid yellow tones. The leaves of Canadian Redbud trees are dark red in colour during vegetation and turn bright yellow in the fall.

For each of the three species, in turn, there are some varieties that are very popular because of their different characteristics:

• Common Redbud tree ‘Alba‘: Variety widely used in our country, grows to a maximum height of only 2.5 m, green leaves and white flowers, needs protection from frost especially when young.
• Common Judas Tree ‘Rubra‘: Up to 8 m tall, bold dark red flowers, gray-green foliage, frost protection is needed especially when young.
• Canadian Redbud tree ‘Merlot‘: Grows up to 4 m high, special play of colours by foliage and flowers, dark red colour of leaves reminds of red wine Merlot.
• Canadian Judas Tree ‘Ruby Falls‘: Up to 4 m tall, hanging Redbud tree, strong red foliage, purple flowers from April, very dense flowerhead, very frost hardy.
• Canadian Judas Tree ‘Hearts of Gold‘: Grows to circa 4 m tall, golden-yellow foliage colouration and whitish-purple flowers, not very frost hardy.
• Chinese Judas Tree ‘Avondale‘: Grows up to 2.5 m tall, purple-red flowers, leaves are green during vegetation and get a strong yellow fall colour.

Planting Judas trees: location and procedure

The Redbud tree grows naturally in sparse forests or as pioneer vegetation on calcareous soils at altitudes below 400 metres. In the home garden, it should ideally be planted in sandy, well-drained soil. Moderately dry to dry soils are just right for the Redbud tree in this regard. This lime-loving plant also tolerates slightly acidic soils, and it greatly benefits from an application of lime at planting time. Very heavy, clay-rich soils as well as very humus-rich soils should be improved by large-scale and deep admixture of sand. Full sun to sunny, wind-protected locations are well suited for the Redbud tree.

The best time for planting is spring, as soon as frost can be excluded. To plant the Redbud tree in the garden, you can dig a hole with a spade, insert the planting ball and cover with soil. As a rule of thumb, the hole should be about 1.5 times as wide and as deep as the bale. Light pressing and good watering, preferably using a watering ring around the trunk, will encourage the Redbud tree to grow. Tall trunks and large Redbud trees should be tied to two stakes so that above-ground trunk movement does not interfere with growing. The tree is suitable only as a young plant for keeping in a container, because the Redbud tree is a deep rooter and hardly forms secondary and fine roots. From most varieties, with proper pruning, you can also grow a Redbud tree tall trunk. For lovers of bonsai Redbud tree bonsai is also well suited, because through a targeted pruning and proper care also succeeds in this art form.

Caring for the redbud tree: pruning, fertilising etc.

The Judas tree is a very low-maintenance plant. Pruning is rarely necessary, because the large shrub naturally grows very picturesque, and pruning would destroy this appearance. If necessary, the Redbud tree can be pruned in the fall after the end of vegetation. You should cut off no more than one-third of the length of the shoots, because it can not tolerate too severe pruning. Infested and dead plant parts can be regularly removed, however. Because of the deep-reaching main root, the Redbud tree is able to mobilise nutrients from deep soil layers and therefore does not require additional fertilisation. Watering is also usually not necessary, because the plant can easily withstand great heat and shorter periods of drought due to its root system. It should be watered only during prolonged periods of drought.

Tip: The roots of the freshly planted Redbud tree are not yet developed enough to absorb all the important nutrients from the soil. Nevertheless, to provide it with the best possible nutrients, you can fertilise the Redbud tree with a slow-release fertiliser such as our Plantura All Purpose Plant Food.

Propagating redbud tree

Propagation of Redbud trees, unfortunately, is not always successful, as germination is inhibited by a hardened seed coat. The seeds should still be sown again in the fall, immediately after ripening. To do this, the seeds should be soaked in water for about a day, and then put in potting soil. In a bright place and using a seed tray, with regular watering, there is a chance that the Redbud tree seeds will germinate. About 10 cm tall seedlings should be pricked and continue to water regularly.
Alternatively, in summer, cut branch cuttings about 15 cm long diagonally with a sharp knife and stick them about 5 cm deep in growing soil. If the soil is kept well moist, the Redbud tree will form new roots after some time in a bright place. Once new shoots are formed, the cutting can be repotted and grown into a young plant. But beware: the young plants are very sensitive to cold and should remain indoors, especially during the winter.

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Is the Redbud tree hardy?

The Canadian Redbud tree often tolerates cold without problems. However, the common Redbud tree, especially as a young plant, must be protected outdoors with a fleece or by painting with lime for the first three to five years. Otherwise, as a result of the cold, frost cracks may occur on the trunk and branches. It is advisable to plant the young plants as a pot culture before they are later planted in the open ground, as they can move to the species in winter in a frost-free winter quarters. As winter quarters are suitable only cool places, because the Redbud tree needs cold temperatures to activate its buds for the coming year. At 0 to 5°C in a bright shed, garage or unheated greenhouse tree winters safely and naturally. As soon as prolonged frosts are no longer expected, the young Redbud tree can be brought back outdoors. Older plants can safely survive the winter outdoors, as they are usually hardy and frost-resistant.

Common diseases and pests

In general, the Redbud tree has no problems with diseases and pests. Very rarely, wilting is caused by an infestation of the Verticillium fungus, which clogs the water-conducting vessels called xylem, causing individual leaves, branches, or the entire tree to wilt. But when the Redbud tree shows withered leaves, it is often already too late. Only radical pruning can then possibly help the tree.

Is the Redbud tree poisonous?

Redbud trees are usually used as ornamental shrubs, but their flowers are edible raw and have a slightly sweet and sour taste. Thus, they are the ideal edible decoration for salad. In addition, the flower buds can be pickled and used as a spice. The legumes, on the other hand, are slightly poisonous and therefore should not be eaten.

Are you happy to see different colours of flowers already in the spring? Then also read our article about bright yellow flowering winter jasmine.