Pests & Diseases

Tradescantia (Andersoniana Group) ‘Blue Stone’

By far and away the worst problem suffered by hardy Tradescantia species and cultivars is leaf streaking and spotting. These unsightly fungal infections or environmental problems are usually most evident towards the end of the main flowering period, late June and early July in the UK. They often indicate that a plant is under stress and is therefore prone to attack by fungal spores. This stress can often be brought on by nutrient deficiency, water deficiency or environmental conditions such as humidity or lack of air circulation. Applications of high nitrogen feed early in the season can produce lush green growth which is particularly susceptible to fungal diseases. Not all plants will suffer at the same time or to the same extent but, in a detailed 5 year study of Tradescantia Andersoniana Group cultivars between 2005 and 2009, botanists at Chicago Botanic Garden concluded that ALL plants suffered from leaf spotting at some point during the trial, some worse than others, and some only in some years, but no plants escaped this problem completely. The following table of their findings details the results in the final column.

Table 1: Plant Traits and Ratings

OverallTradescantia1FlowerFlowerBloom Period2LeafPlantPlantLeaf
Rating ColorSize ColorHeightWidthSpotting3
★★★★‘Angel Eyes’white, purple1¼ in.early Jun-late Sepgreen18 in.32 in.low
★★★★‘Bilberry Ice’ (AG)white, lavender1½ in.early Jun-mid Sepgreen22 in.36 in.low
★★★‘Blue and Gold’ (AG)purple blue1¾ in.late May-mid Sepyellow16 in.30 in.moderate
★★★★‘Blue Stone’ (AG)lavender blue2 in.mid May-late Sepyellow green22 in.36 in.low
★★★★‘Concord Grape’ (AG)purple1½ in.mid May-Sepblue green24 in.36 in.low
★★★★‘Danielle’ (AG)white2 in.late May-mid Augyellow green20 in.32 in.low
★★★‘Innocence’ (AG)white2 in.early Jun-Sepyellow green16 in.30 in.moderate
★★★★‘Jeannene’purple1½ in.late May-late Sepgreen20 in.34 in.low
★★★‘Karminglut’ (AG)purple2 in.early Jun-Sepyellow green22 in.40 in.moderate
★★★‘Little Doll’ (AG)light blue1½ in.late May-mid Sepgreen12 in.32 in.severe
★★★‘Lord Nelson’dark purple1 in.early Jun-late Augblue green15 in.26 in.low
★★★‘Mariella’ (AG)purple blue2 in.early Jun-Sepgreen20 in.36 in.moderate
★★★★‘Mrs. Loewer’ (AG)lavender blue1½ in.mid Jun-mid Sepblue green18 in.34 in.low
★★★★‘Perinne’s Pink’ (AG)pink1½ in.early Jun-late Sepblue green24 in.40 in.low
★★★★‘Purple Profusion’light purple1¾ in.mid May-mid Sepblue green15 in.30 in.low
★★★‘Red Cloud’rosy red1¼ in.mid May-late Julgreen24 in.60 in.low
★★★★‘Red Grape’ (AG)magenta1½ in.mid Jun-mid Sepblue green24 in.36 in.low
★★★‘Rubra’ (AG)deep violet1½ in.early Jun-mid Sepgreen20 in.36 in.low
★★★‘Snowcap’white1½ in.late May-mid Augyellow green20 in.32 in.moderate
★★★‘Sylvana’ (AG)violet magenta1¾ in.early Jun-early Octgreen22 in.30 in.severe
★★★★‘Therese’pink1½ in.early Jun-Sepgray green24 in.30 in.low
★★★‘Valour’ (AG)purple1½ in.late May-early Sepgreen18 in.30 in.moderate
★★★‘White Doll’white1½ in.early Jun-mid Sepyellow green18 in.32 in.severe
★★★★‘Zwanenburg Blue’ (AG)purple blue2 in.late May-mid Sepgreen20 in.36 in.low
★★★★ohiensislavender blue1¼ in.mid Jun-early Sepblue green18 in.36 in.low
★★★★virginiana ‘Caerulea Plena’blue, double1½ in.early Jun-early Auggreen24 in.34 in.low

Overall Ratings: ★★★★★ excellent, ★★★★ good, ★★★ fair, ★★ poor, ★ very poor

1 (AG) designates Andersoniana Group per Royal Horticultural Society

2 Bloom Period: inclusive of initial bloom cycle and subsequent late-season flowering

3 Leaf Spotting: severe >50%; moderate 21-50%; low <20%

As can be seen from the first picture above and the following picture of T. ‘Charlotte’ in my own Collection in 2021, this can be a very unsightly problem and, if not addressed, could result in a serious weakening of the plant and even death.

Fungal leaf infection on Tradescantia ‘Charlotte’ 16th July 2021

I am led to believe that these infections can be minimised in the following ways:

  • High Sulphate of Potash feed rather than nitrogenous feed in the flowering season.
  • Organic fungicide treatment such as Bicarbonate of Soda as a foliar spray
  • Repeated applications of a commercial fungicide treatment containing Triticonazole, Tebuconazole or Trifloxystrobin such as Provanto Fungus Fighter or Fungus Clear Ultra.
  • Monitoring and maintaining adequate hydration and air circulation.

In 2022 and future years, plants will be carefully monitored and different treatments applied to maintain plant health and check the efficacy of organic v chemical treatments.

Overwintering slugs and snails are apparently partial to emerging young growth but, as yet, I have not found this to be a problem. I have not applied any mollusc deterrents or slug bait but might do so if it became necessary.