National Transport and Wildlife Corridors-Roadside Wildflora-Using Native Irish Wildflowers

 
 

Brief Guidelines for Roadside Landscaping with Wildflowers: 

Some basic standard general tips on planting wildflowers. 

 

The following brief guidelines are for planting wildflowers on roadside landscapes.
Our experience is that Irish roadside planners did not sow wildflowers on roadsides due to a general inexperience throughout the Roadside Design sector regarding species choice, correct sowing, placement and management.  Furthermore the industry once suffered lack of funds and insecurity about the appearance of wildflowers. Sometimes flora did not grow as the wrong or inappropriate species were used. Other times the Landscape Contractor did not sow them correctly nor were they managed in the early years. The perceived costs involved further restricted the use of native flora. In the final analysis we think that the species used were unsuitable for the non-cutting regimes on roadside embankments and cuttings.  

Richard Webb of An Foras Forbaintha was one of the first to use native flora, in an Irish situation.  Sadly the seed was imported from British sources and some of the species failed to grow.

Where species establishment was successful, I observed mixtures of species that required cutting, which did not happen and today only one or two species still exist. 

On the Newtownmountkennedy By-Pass, Co. Wicklow, (sown late 1980's) some species grew, but failed due to no cutting.  Recently due to pipe laying some species re-emerged.  Here the problem is that these species can be seen as native stock by future generations of wildflower pickers. 

We Recommend 

We recommend planting robust mixtures that do not require cutting and are from locally occurring species with additions of species found in the region on similar soils.

Our species choice is designed to stabilise road embankments and cuttings as well as attract wildlife and flower providing interesting roadside colour.

The reasons to plant native flora are discussed elsewhere. DBN specialise in site specific design for flora and further will also pick locally occurring species best suited to the area 

Site Survey

Large roadside projects should include a site survey which DBN can carry out.  

A site survey reveals the actual composition of flora, (unlike Impact assessments which use the county register of flora, and is not necessarily site specific). To encourage native flora, the soils, plant communities and natural succession are all surveyed along with wildlife corridors. The resulting information provides information to make recommendations.

The DBN experience

DBN Experience. Because DBN grow and manage native flora we are familiar with each situation where native flora will grow, based on our site survey we make recommendations as to cost effectively sow or encourage native flora. Often the site survey reveals floras or soils containing floras that can be protected and re-established on the roadside.

Species choice

Species choice depends on many factors, the wild flora must become a sustainable low or no maintenance flora and survive no or little cutting.

Native floras used on roadsides should be tolerant of the extreme stresses found on verges and steep sided embankments.

All mixtures with or without grasses

Where the site survey reveals specific soil types, floras or micro climate suitable for the establishment of flora, the following are the main groups of roadside seed mixture supplied by DBN:

Species and mixtures that require no cutting:

  • Shade or Hedgerow, Wetland, or marsh
  • Wildlife attracting species
  • Specifically designed moist or dry acid soil mixtures.
  • Specifically designed moist or damp alkaline or neutral soils
  • "No cut" mixtures are available for sand, peat, clay and silt or fertile loam
  • Tall, short, early, late flowering or single colour mixtures provide further  choice
  • However the best mixtures are derived from plant communities that locally occur in the area.

Top soil

Where at all possible the stripped away soils taken during construction should be stored correctly and reused back on the roadside landscape.

While this information seems obvious, rarely are soils properly stored or labelled to allow the correct spreading often years later. Weeds are killed when the soil is re-spread.  

If a weed invasion occurs, seek advice before re-spraying, certain weeds are very useful as a nurse crop.

Sub soil, certain base ,second or sun soils

These in-earth soils are unique in that they occur specifically in that locality, if spread elsewhere they can become inappropriate to the landscape. Such site specific soils must be reused to best effect to enhance the exact area where they were excavated from. 

These sub soils are perfect for the establishment of many native flora mixtures. Provided they are fed, or covered in a 30mm-80mm layer of top soil. 

Soil Spreading

The approach that must be taken by the contractor is that soil is a precious commodity and should be used sparingly.

For standard wildflower sowings top soil can be spread to an absolute maximum depth of 150 mm, especially where the sub soil is heavily compacted. 

DBN recommends very shallow spreading of subsoil from 40 - 70mm, this will ensure enough nutrients to get grasses and flora started and adequate water holding potential so that the roadside does not dry out in the early years of seedling establishment.

Where no top soil is found, fertiliser (16 - 40 kg per Ha ) will be required to establish flora especially where grasses are used on second soil.  The second soil needs to be carefully spread and not compacted above 150mm.

A special method of sowing compacted soil on very steep soils has been developed at DBN.

Sowing rates

Native wild flowers are normally sown at 1.5gms per metre. High rates of 3gms per metre can be used in important areas or where the soil is very poor. 

Where ideal conditions prevail as for farmland,  as low as 0.75gms can be sown.

The higher rates of 3gms are best used on roundabouts, key junctions and in areas where colour is required.

Hydra seeding

There are now three main Hydraseeding units in Ireland. Where wildflowers have been hydrasown the results are varying, however when properly used the method works well provided the sowing is carried out at the optimum sowing times of mid spring and early autumn.  We prefer hand sowing and hydraseeding the grass later.

If the weather dries up a crust can form lifting the hydraseed of the soil, killing the seedlings.

Flora with and without grasses

Grasses should be used to control erosion and where the amenity value is required,

There are many situations where grass is inappropriate such as mid way down a steep dry slope as it tends to yellow very early and become a fire hazard.

Grasses act as a nurse crop for wild flora and attract many species of wildlife mainly butterfly. Grasses mixed with native flora are available at 20%, 30%, 50% and 80% grass.

Price

DBN supplies mixtures with at below UK cost for equivalent 28-35 species mixture.
Imported seed mixtures can seem less expensive when buying only 6 species, but on species per species comparison on 35 species DBN are less expensive and our seed is native and often site specific local.

Where long term contracts are placed to grow flora for specific roadwork's, then DBN wildflower mixtures are even better priced.

DBN offer a site survey service from which further cost savings can occur.
Exact prices are very difficult to quote from this web site, on average mixtures vary from Euro() 170 - per kg to Euro() 200 - per kg of PURE WILDFLOWERS NO GRASSES depending on species composition and numbers. 
If DBN are asked to carry out a site survey we will be able to place appropriate species in a cost effective manner. For instance the top of embankments are very different to the mid-slope and base, the planting and cost should acknowledge this.

DBN will be updating this page with examples of planting and further advice.
Watch out or update pages on Roadside projects.

DBN (Ire) - Irish Native Origin Wildflower Growers - Working on the Wildside

 

 
 

 

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