Testing Time for Yuccas

A self-confessed Yuccaphile shares his passion for these architectural but unfriendly plants.
Marco Tiefel, Austrasse 1, 91126 Schwabach, Germany
Chamaerops No.30 Spring 1998

Look but don't touch: Yucca aloifolia - Spanish Bayonet - with leaf tips like needles

Two hard winters in succession had a very dispiriting effect on German palm enthusiasts. The 'Spanish Bayonet', Yucca aloifolia "Variegata" has not survived the winter of 1996. Though the temperatures were below minus 15° Celsius "only" once, there were six weeks of permanent frost in January and February.

My Trachycarpus with a height of about two meters, planted in 1990 as has been reported in Chamaerops No. 24, did not get on much better. After the leaves had died off, I hoped for a new sprout, but the closed leaves could be pulled out. The cold spring and the rainy summer of 1996 as well as the autumn were of no help. On one occasion I thought that my Trachycarpus was about to come out again, but in the softened funnel of the trunk water accumulated. So here is my advice: whoever thinks his Trachycarpus lost, should immediately after the dissolution of the leaves cut back the top of the trunk a little bit, so that the fertile cone in the midst doesn't drown. This gives the Trachycarpus a last chance. Now my second Trachycarpus, which has already spent the winter of 1992/93 outside, at that time with damage to the leaves at 16°C below zero, will get its chance.

With a little trick, Musa basjoo starts into the winter: before planting, I dug a heating cable into the ground. There is some good news, too. Although the winter of 1997 had been cold, too, with almost four weeks of permanent frost from Christmas till the 18th of January and twenty nights with temperatures of about minus 20°C, the Araucaria araucana, whose lower branches had become brown, has kept an intact tip which has come out again. The 'Spanish Dagger', Yucca gloriosa, got away unharmed this time, despite having been placed on the windy eastern side of the house. Did the advantage lie in the more rain sheltered, dry position on the eastern side or that after very cold, clear frosty nights the morning sun could warm up the plants somewhat again? I don't know.

Yucca gloriosa has proven itself undoubtedly as the hardiest trunk-developing variety. This variety, with a main flowering period in June, is frequently to be found around Lake Garda, where many plants can still be seen flowering in September and October. Yucca gloriosa is also the most fertile of it's kind. Being left for two to three years in the same pot, it produces so many sturdy groundshoots that these can burst the pot. Recently found more often in German garden-centres is Yucca gloriosa "Variegata", a very beautiful variety with colourful leaves, that however doesn't reach the growing strength of the original form. In any collection of subtropical plants, the trunkless species Yucca flaccida and Yucca filamentosa, which are also suitable for very cold regions, should not be missed. Yucca flaccida has smaller leaves and blossoms. A fabulous species is Yucca flaccida "Aureovariegata", with vivid yellow parts in the leaves.

The giant Yucca elephantipes, in Germany usually offered as an indoor plant, will of course grow much stronger if kept outside during the summer. In the house the leaves become too thin and will later hang down unsightly. Tests concerning the frost resistance of this variety have shown that on plants, that have survived temperatures of minus 6°C in late autumn, in the cool winterquarters the main shoot can still die off. On the opposite temperatures of minus 7°C in the spring have been tolerated without any harm, which may have to do with the increasing amount of light in springtime. These results also apply to the colourful types of Yucca elephantipes such as "Variegata", "Juwel" or "Silverstar".

A very special recommendation is Yucca rostrata. It is hardly ever available on the market and large plants have a high price. Mine is 1,70 meters high, the trunk is 1,20 meters tall with a circumference of 40 centimeters almost evenly up its entire length. It has a nice effect to cut back the dead leaves to an even length as this gives the trunk an interesting pattern. The bluish, only one centimeter broad leaves are about 40 centimeters long and form a round crown, similar to a great Dasylirion. In just one summer almost a hundred new leaves can be produced on each plant.

Unfortunately, very little is to be found in literature about this variety or its frost resistance. My plant has already tolerated minus 3°C without any damage. I hope, that by reading this article some readers might develop an interest in Yuccas, beautiful and rewarding plants.