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Hillier Urges UK Horticultural Industry to Develop Improved Tree Cultivars

The UK has a fantastic, thriving, horticultural industry. When it comes to the development of new and improved tree cultivars and clones however, some architects, designers and landscape contractors are still looking outside our borders for the best varieties. With relatively few new tree cultivars being developed in the UK, Hillier Trees is urging the industry to renew its focus on developing varieties for the UK environment, with the accompanying positive effects for the local industry and biosecurity benefits.

Hillier Trees has developed a number of cultivars that are now in widespread use across the UK. This includes the Hillier ‘Streetwise’ range, designed specifically for the growing number of tightly packed urban and suburban locations across the UK. This range has been developed by Hossein Arshadi, Divisional Director at Hillier Nurseries, over a period of many years to suit the modern urban environment and ensure our native trees can still thrive in these tricky urban spots.

Hillier Trees would welcome the development of more tree ranges designed specifically to meet the evolving needs of our local landscapes.


Acer campestre ‘Streetwise’

The field maple is a native tree that has been traditionally been planted among hedgerows and in open rural locations. Due to the unpredictable growth of its canopy, it is not a tree that naturally fits the high demands of inner-city urban planting.

With the desire to create a uniform and consistent cultivar, Hossein took cuttings from five specific field maples growing on Hillier Trees field nurseries that exhibited defined, upright branches. These five trees were propagated every 12 months and monitored for specific qualities, including outstanding autumn colour, pest and disease resistance, canopy shape and growth. After 18 years of propagation and thorough analysis, Hossein selected the best cultivar for performance against all these qualities, which is now available as the Acer campestre ‘Streetwise’ selection.

Acer campestre ‘Streetwise’ is exceptionally hardy, responding well to pruning schedules and yearly maintenance. Its upright, consistent canopy is ideal for locations with vehicle and pedestrian traffic, including carparks, central reservations and pathways. It is tolerant of all soil types, as it is both drought and waterlogging resistant. Being native, it is a valuable tree for bees and butterflies. The keys specific to this cultivar develop into a profound cardinal red as the summer fades and the leaves are a deep emerald green, which develops into the most spectacular autumn gold of all our native trees


Hippophae salicifolia ‘Streetwise’

The creation of a ‘Streetwise’ version of sea buckthorn came off the back of a visit to Sir Harold Hillier Gardens in Hampshire. During the tour, Hossein discovered an unusual Hippophae multi-stem shrub with curious upright branches, that he believed could work brilliantly as a street tree.

Hippophae salicifolia ‘Streetwise’ is an excellent choice for city applications. It tolerates all urban issues, including pollution and salt spreading. It has been used in difficult locations throughout London with great success.

The tree presents with branches that are mainly ascending, with a few lateral for the canopy to remain open and light. These branches are also less thorny than the well-known Hippophae rhamnoides (seaberry) shrub. Its leaves are long and willow-like, opening a fresh subtle green, with an almost white underside. The bright orange fruit develops in October, ready to support wildlife with winter nutrients. The berries are renowned as superfoods with amazing health benefits and are enjoyed by birds and humans alike.


Sorbus aucuparia ‘Streetwise’

This clonal selection of mountain ash, introduced by Hillier in 1998, was raised by Hossein Arshadi in the early 1980s at Hillier Tree Nurseries. This particular cultivar stood out as being an extremely robust grower, quick to establish at every stage of production.

Sorbus aucuparia ‘Streetwise’ has a very neat, upright habit and its narrow, compact canopy makes this the best of the species for street and urban planting. Its vigour ensures that it establishes quickly on site, even in harsh conditions. The strongly ascending branch structure maintains the upright, tidy form throughout its maturity.

This tree is free fruiting, with bright orange berries from July to November having produced corymbs of attractive white flowers in May and early June. The leaves are mid to dark green becoming orange-yellow in the autumn. The berries are very attractive to birds, so are almost always eaten while still on the tree.


Tilia cordata ‘Streetwise’

Tilia cordata ‘Streetwise’ is a tree cultivated, introduced, and a personal favourite of Hossein Arshadi, the Divisional Director of Hillier Trees. This is part of the famous Hillier Streetwise selection, cultivated to ensure the continued planting of our native trees within the expanding urban environments.

This seedling was first raised from mature lime trees in 1982. It was conspicuous thanks to its ‘well-behaved’ characteristics and uniformed canopy of ascending branches. Its healthy vigour very clearly set it apart from the other seedlings, and as the years progressed, these beneficial characteristics continued through to maturity.

Tilia cordata ‘Streetwise’ has become a significant rival to the industry-known Tilia ‘Greenspire’, proving to be a better-suited tree for urban applications. It has a noticeably faster growth rate than T. ‘Greenspire’, being consistently one nursery girth size larger at the same age. The leaves are also noticeably darker. This is due to the increased quantity of chloroplasts that contain the chlorophyll, which highly absorbs sunlight with low reflectance. This ensures the T. cordata ‘Streetwise’ has exceptional tolerance to periods of drought and heat. On the hottest days of the year, where other Tilia leaves are wilting, its leaves consistently remain vibrant and healthy.

As the days progress and the summer becomes hotter, the new leaves of T. cordata ‘Streetwise’ open with much larger width and size to the first leaves produced. These larger leaves then quickly develop the same darker shades of green. By the autumn, the dark leaves have grown many times the size of the Greenspire. This larger size, thicker leaf with additional chloroplasts, along with its upright ascending canopy, make it the perfect tree for the difficult conditions of street urban planting.

Come autumn, the leaves melt into buttery shades of gold, creating the most wonderful urban displays when planted as avenues. This vibrant colour is further accentuated by its uniformed, upright canopy. Like the species, the ‘Streetwise’ linden is attractive to bees and many other insects but is its thicker leaf significantly reduces the issue with Aphids, making it perfect for urban amenity.


Hossein Arshadi Biography

Position

Divisional Director at Hillier Nurseries

Education

Horticultural Studies at Hadlow College and Business Studies at Portsmouth University.

Career

Having initially intended to be a building architect, Hossein changed direction to a career in horticulture after spending a summer working at a nursery and getting to like the industry.

Hossein joined Hillier in 1980 within the Amenity division, which at that time grew trees and shrubs for business customers. He worked his way up through the company, with roles in Production, Sales and Management. Hossein has been a Company Director at Hillier since 1999 and has overseen major developments in the selection, quality and scale of tree production at Hillier.

Horticulture Highlights

One of the most important decisions for the Hillier Trees division has been the move towards growing large, semi-mature trees, orchestrated by Hossein. He set the objective for Hillier Trees to be the market leader in the UK, an objective which has been realised in terms of tree volume, quality and size.

This move towards quality, semi-mature trees at scale has set Hillier Trees in good stead for prominent projects. One of the most significant of these was the Olympic Park project in 2012. Hillier Trees was shortlisted as a competent nursery to compete and ultimately won the contract, supplying all trees for the whole of the park.

The door has also been opened to numerous mid to large size projects requiring bigger trees, with Hillier Trees the only nursery in the UK capable of supplying these at volume.