How to establish wildflowers

Basic planning


Wild flowers will not ‘just grow anywhere’. Some plants only grow on certain soils and in certain conditions. Most do not grow well if they have to compete with pernicious weeds or vigorous grasses, and they will give the best ecological value and the most pleasure if the right plants are grown in the right place.


So sit down and have a think. You have some land on which you would like to see wildflowers growing. Analyse your reasons: To support biodiversity? To give you pleasure with their variety and colour? To improve the landscape? To educate the visiting public? To attract birds, butterflies, bees or other beneficial insects? To justify infrequent cutting of a grassy area? To distract from an eyesore?


All of these objectives are valid, whether in a suburban garden, a country park, roadside verge or working farm. Consider them in relation to the ways in which adjacent land is used and how wildflowers can improve the value (wildlife, aesthetic or monetary) of the whole area. Are there areas of high ecological or landscape value nearby? Consider the season(s) at which you wish your planting be at its best. How much time do you want to spend maintaining the area in future years? Would you, or your client, like some flowers in the first summer or is it acceptable to wait until the perennials reach flowering stage in the second year after sowing?


Take a spade and check what soil type you have.


Armed with this information, you can choose the appropriate wildflower mixture to suit the site and your objectives. If improving biodiversity is an important aim, or if the project is within an area of high landscape or ecological value, you should choose ‘local-origin seed’ (which poses minimal threat to the local ecology). The same is true for highly fertile sites, where genuinely wild grasses such as Herbiseed’s Park Meadow’ will be less vigorously competitive than cultivated varieties. For other sites, and to meet purely aesthetic (rather than ‘ecological’) objectives, the use of generic ‘British native seed’ is acceptable, and may offer a greater range of choices than the limited choices of ‘local-origin’ and ‘organic’ seed available at present.


The Herbiseed list comprises seed mixtures for most soil types in Britain, plus a few mixtures composed of ‘generalist’ species which are not fussy about soil characteristics and can be relied on to succeed on almost any soil type. Finally, if no standard mixture suits your requirements, discuss your requirements with Herbiseed, and our ecologist will suggest possible bespoke solutions .


Most wildflower mixtures are composed of 80% grass seed and 20% wildflower seed because a pure stand of wildflowers tends to leave bare areas in the winter which look unsightly and allow weeds to establish. These 80:20 mixtures produce a ‘meadow’ which appears as a mixture of grasses and wildflowers in the growing season but can be cut in the autumn and managed as mown grass during winter. However, should you wish to enhance an existing grass field, choose the 100% pure wildflower mix version of a standard seed mixture and sow that directly into the grass or use pot-grown plants (see below for methods).


Herbiseed’s ‘Cornfield Annual Spectacular’ can be added at 5% for moderately fertile soils and 10% for low fertility soils to produce a scattering of poppies, corncockle and cornflowers in the first year which provides interest before the perennial species flower in the second year.


Preparing the site


1) First, get rid of all perennial weeds such as nettles, docks and thistles, possibly by spraying them with an appropriate weedkiller.


2) Next, aim to achieve a moderate to low fertility in the top 15 cm. of the soil. Where the fertility is too high, weeds and grasses grow faster than the wildflowers (If high fertility is unavoidable, use a mixture based on Herbiseed’s ‘Park Meadow’ wild grasses which are less vigorous than agricultural grass varieties and less mat-forming than cultivated varieties of red fescue).


Soil fertility can be lowered by scraping off the topsoil, leaving no more than 10 cm. of topsoil above the subsoil and if possible, ploughing to a depth of 25cm to mix subsoil and topsoil. Another method is to mix a 15 cm. layer of crushed brick rubble or stone with the top 10-15 cm. of soil


Conversely, although it is possible to establish some wildflowers on pure subsoil, if the subsoil is pure clay, the establishment phase is much shorter and more reliable if 5-10 cm. of topsoil is applied to the surface of the subsoil.


Fertiliser is not required at any time for wildflowers except on the most extreme sites where no natural soil is present. On industrial and demolition sites, a substrate of crushed brick, rubble or slag will support pioneer species (such as mixture WF29) provided it is well compacted and a dressing of nitrogen (as urea) and phosphate is applied. On such sites spreading even a few millimetres of topsoil can greatly accelerate vegetation establishment. On acid substrates such as coal mining waste, lime may be required to reduce soil acidity. All industrial wastes are easier to vegetate if they have been weathered for a few years and the weathered surface layer not buried before sowing.


3) Cultivate the site to a depth of at least 10 cm. (on badly drained or compacted soils, plough to at least 25 cm.) and prepare a fine tilth. Do this as early as possible, ideally two months before the planned sowing date, to encourage any weed seeds in the surface soil to germinate.


4) Control Weeds before sowing wildflowers. Whenever a flush of weeds reaches 2 cm. high kill them with a non-residual herbicide such as glyphosate (do not cultivate or disturb the soil surface because the objective is to exhaust the weed seed bank in the upper centimetre of the soil). If subsequent flushes of weeds appear kill them in the same way without disturbing the soil surface.


Seed sowing


On large projects the ideal time for sowing wildflower mixtures is the last week in August or first week in September. This avoids the dry soil conditions of summer but gives the seedlings sufficient time to become established before winter. Spring sowing from March onwards is usually successful, although it should be avoided on soils with a large weed seed bank (lots of weeds are programmed to germinate in spring). In high rainfall areas, or where watering is possible, seed can be sown at any time of year provided that weed pressure is acceptable.


Immediately before sowing, kill any weeds which are present with a non-residual weedkiller but do not cultivate the soil surface.


Broadcast the seed by hand or fertiliser distributor. Rake or harrow it into the top 3 mm. of soil surface (not deeper than 3 mm.!). If desired the seed can be mixed with sawdust (available as cat-litter from a pet shop) to aid achieving an even distribution of the seed. Ensure that the seed, and sawdust if used, is well mixed before and during sowing.


Roll, preferably with a ribbed roller. However, do not roll late autumn sowings, because there is usually plenty of available soil water for germination and rolling before winter tends to cap the soil.




In the first season after sowing, weed control is a priority. If weeds are present they can be controlled by mowing. Each time the vegetation reaches 15 cm. cut it back to 10 cm. Most of the wildflowers are biennials or perennials. They spend their first summer building a rosette of leaves close to the soil, so are not significantly harmed by this mowing regime. If no weeds are present, cut the vegetation to 10 cm. every time the grasses reach 20cm to prevent the grasses out-competing the slower growing wildflowers. Remove the cut vegetation to prevent it smothering the wildflowers.


If ‘Cornfield Annual Spectacular’ has been added to a perennial wildflower sowing, the poppies and cornflowers will be detrimentally affected by cutting, so unless weeds are present, do not cut the area until they have finished flowering. However, if a significant weed population develops, give priority to weed control!




In the second year after planting, the grass and wildflowers will be established and annual weeds will be less of a threat. Maintain wildflower and grass areas as short grassland or lawn from October to March. The ‘October’ mowing should be timed for just after the last flush of flowers set seed in the autumn. The timing of the spring cut is critical, needing to be just before the first wildflowers (usually cowslip but earlier if you have planted spring bulbs into the area) send up their flowers. These two cuts should be adequate for most wildflower meadows. A single autumn cut may be appropriate in agri-environment schemes and roadside verges. More domestic situations such as ‘flowering lawn’ are best if one or two additional cuts are timed between flushes of flowers during summer. Always remove the cuttings to prevent them smothering grass or wildflowers.



Sowing Wildflowers Into Existing Grassland


A pure wildflower mixture can be used to improve the biodiversity of existing grassland using the following technique:


• Manage an existing permanent grass field or lawn to remove all perennial weeds such as nettles, thistles and docks, using a selective herbicide if necessary. Neglected pony paddocks in particular need a year of treatment to remove nettles, thistles and docks!


• Cut or sheep-graze (cow pats are undesirable) the existing grass as close as possible to the soil.


• Severely scarify the grass with several passes of a spring-tine harrow or rigid tine cultivator. The object is to create at least 50% bare soil. On sites where a month of moist soil can be expected, create at least 70% bare soil, possibly using a single shallow pass with a rotavator.


• Immediately the scarification is complete, before the top dries, broadcast the wildflower seed, using sawdust or coarsely ground barley meal (Not sand which is much heavier than seed!) as an extender if desired.


• Roll with a ribbed roll, if necessary make several passes on light soils to produce a firm but not puddled surface.


• In the first year after sowing, use periodic mowing down to 10 cm. to control weeds and suppress the grass. This will not significantly damage the biennial and perennial wildflowers which form a rosette of leaves close to the soil in their first year. Do not leave dense wet mown material on the area as it may prevent wildflower establishment.


• Be particularly vigilant for weeds in the first year of establishment if the wildflowers are sown into land with a recent history of arable farming, as there may be a large soil seed bank. In this case, more frequent mowing may be necessary.



Planting wildflower plugs and pot plants into established vegetation.


Plug plants are 6-8 week old seedlings grown in modules of compost measuring typically 3cm. x 3cm. x 4 cm. They can be rapidly planted with a trowel or dibber and grow on immediately. Planting plugs also enables individual plants to be positioned intentionally in the planted area, so tall plants can be planted at the back, short plants at the front, special species planted in drifts in certain areas, other species concentrated in other areas.


Plug plants of wildflowers can be introduced into an area newly seeded with grass seed or a wildflower mixture. The head start that plug plants have over the new seed enables them to establish faster than the grass, and often plugged perennials will flower in the first season after planting.


Wildflower plugs, or better the larger, more competitive plants grown in 11cm pots, can be used to introduce wildflowers into established vegetation such as a lawn or permanent pasture. This tends to be most successful on sites with good soil structure, medium to low soil fertility and abundant moisture. It also requires the grass to be temporarily suppressed to reduce its competition with the introduced plugs. Try one of the following techniques:


• Scarify the grass very heavily, even shallowly rotavate it in a single pass, so that about 30%-50% of the area shows green. Plant the plugs or pot plants immediately before the surface dries, then roll with a flat roller to produce a firm but not puddled surface. Do not use the rotavator technique between May and September unless you are in a very high rainfall area.




• A modification of this technique is to use a rotavator specially designed to cut 30%-50% of the area, leaving the remainder of the grass intact. Tractor-mounted machines of this type are rare in Britain. However sets of ‘Virgin Land’ straight blades can be purchased for some models of pedestrian controlled rotavators which achieve the same effect. Plant into the cultivated strips and roll well.




• Professional operators with the appropriate qualifications can spray the entire area of grass to be planted with the lowest recommended label rate of ‘Fusilade’ or other selective graminicide 1-3 weeks before planting (different products have different concentrations and this technique is very rate sensitive, so read the label carefully before spraying). This will suppress the stronger growing grasses and leave the slower-growing fescues and meadow grasses. This method is only effective on lawns and permanent pasture and is not suitable for leys and swards with few grass species. Plant the plugs in the treated area (even if the grass still appears green) and firm in well or roll.




• Spray narrow 6-8 cm. wide strips of the grass with glyphosate 2-3 weeks before planting. Plant the plugs into the yellow/brown sprayed strips and firm them in well, or roll the entire area.




With all these plug and pot plant techniques, cutting the grass monthly in the first year will suppress any weed or excess grass growth until the wildflowers are well established.




Whether you are establishing a wildflower area from seed or plants, remember that key requirements for success are good weed control and soil preparation prior to establishment. Effective preparatory work is well worth the effort when considering that a wildflower meadow is a long-term investment in a wildlife-friendly and low maintenance landscape.