Vintage Jade Distylium

Distylium 'Vintage Jade'

Distylium ‘Vintage Jade’ on low water under 50% shade in Davis in July 2019. Photo: SK Reid.

Summary

 ‘Vintage Jade’ is a low-growing plant used as a foliage or “foundation” shrub. It has interesting leathery, bright green leaves that are held on branches that fan out around the center and are held mostly horizontally. It was previously evaluated in the full sun at UC Davis during the 2016-2018 trial, where it did not perform well and frequently showed symptoms of sunburn. To discover if this species would prefer some shade in our Central Valley conditions, we evaluated it under the 50% shade cloth in the 2017-2019 trial. With light but consistent shade, the foliage remained green, with lighter coppery-green new growth and no signs of sunburn. With mean overall appearance scores at open houses between 3.2 and 3.9, participants found this plant acceptable to good (Table 21b).

Plant growth was not significantly different between treatments until October 2019 when the mean high-treatment relative plant growth index was greater than the low treatment (Figure 15b). Half of the plants on the low treatment actually declined in growth over the season, with dieback showing up in August. Another interesting thing to note: Growth on the high treatment began to pull away from the moderate treatment as well as the low in October, though it is not statistically significant at this point. Since the trial ends in October, we can only speculate that this pattern may have continued in subsequent months or years until that difference was significant. Keep in mind that the difference in total irrigation events between the high and moderate is a mere 2 (Table 3). Traditionally the deficit treatment season starts in early/mid-April when rainfall has ended. April measurements are then used as a baseline for the relative plant growth index and May data collection is typically the first instance after treatments have been imposed. However, after the high treatment had received one irrigation, enough rain fell in mid-May to refill the soil profile, effectively delaying any potential treatment effects.

Similar to the measurements pattern, quality ratings in September and October showed significant differences between the high and low treatments, and moderate and low treatments in foliage quality and overall appearance (Table 21a). These two ratings tracked closely since this is a shrub grown for foliage rather than flowers. This led to the average for the year being definitively lower on the low treatment. Overall this plant performed in the good to very good range, with the highest appearance scores on moderate water in September. We recommend ‘Vintage Jade’ be grown in at least partial shade and irrigated on moderate water in WUCOLS region 2.

Growth and Quality Data

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