<em>Mimulus</em>, mimule: planting and care

Description and botany

Mimulus or monkey flower is a herbaceous perennial plant of the family Scrophulariaceae, like snapdragon and Diascia, most often native to wet areas, riverbanks and lakes of Asia, America, Mexico, Australia and South Africa. The genus comprises about 180 species of annual or perennial plants, sometimes shrubby, most of which are tender and therefore usually grown as annuals in our climate. However, some species such as Mimulus luteus, Mimulus ringens, and Mimulus guttatus show some hardiness down to -10°C and sometimes to -20°C. The latter is among the widespread species together with Mimulus cupreus.

There are many cultivars and hybrids derived from Mimulus guttatus and Mimulus luteus, such as Mimulus × hybridus, offered in a wide range of colours and heights.

Depending on species and cultivars, mimulus adopts a variable habit: erect, semi-trailing, trailing or very ground-covering (Mimulus luteus). The smallest varieties do not exceed 20 cm in height for Mimulus cupreus, a dwarf species, while the tallest form bushy clumps of 0.70 up to 1.20 m in height and as much in width for shrubby species such as Mimulus aurantiacus.

Although growth is fairly rapid, mimulus is an ephemeral perennial that benefits from regular propagation to maintain it in the garden; except for hybrid varieties, it readily self-seeds in heavy, moist, clay soils.

Mimulus forms a small shrub, most often very ground-covering with deciduous foliage, rarely evergreen in our climate, except for Mimulus aurantiacus or orange monkey flower.

Mimulus guttatus in flower

Branches, often pubescent, bear opposite leaves, oblong, rounded or linear, entire, slightly to strongly toothed, sessile towards tip of stems and petiolate lower down. Leaves are sometimes covered with a fine velvety layer or sticky. This dense, vigorous foliage, from light green to grey-green, sometimes bronze at first then green, is hidden by long, very generous flowering of mimulus.

Flowers with intense, varied colours appear in the axil of leaves. They open from June to September without interruption, standing out against foliage. Stems, erect, semi-erect or prostrate, end in spikes of 3 to 8 trumpet- or funnel-shaped flowers. Set in hairy calyces, they are composed of 5 fused, rounded petals; two upper petals turned back above three lower lobes, the central lower lobe being wider. These bilabiate corollas with an open, hairy throat evoke a smiling mask with tongue out or the face of a mocking or grimacing monkey. A morphology that earned mimulus the English name ‘Monkey Flower’.

Flower size varies by variety and hybrid. They measure from 2 cm to over 10 cm in diameter for the largest, such as Mimulus × hybridus ‘Maximus Mixed’, which bears giant flowers on average four times larger than most mimulus flowers.

Mimulus flowers are available in an infinite range of vivid monochrome colours from bright yellow, coppery orange (Mimulus cupreus), pink, scarlet red (Mimulus cardinalis) to pastel shades ranging from white, pale violet-blue (Mimulus ringens or blue mimulus) to pale yellow (Mimulus ‘Highland Yellow’).

There are also bicolour varieties, fully marbled or striped, or with throats subtly speckled with a contrasting colour (spotted mimulus or Mimulus guttatus, Mimulus × hybridus ‘Monkey Magic’ F1 Hybrid, ‘Calypso F1’).

Although most mimulus flowers are unscented, some species such as Mimulus moschatus give off a distinctive musky odour, hence another common name “musk-flower”.

This endless flowering is melliferous, attracting many pollinating insects.

Even if some hardy mimulus (down to -15 to -20 °C) can withstand cold, most hybrids are tender perennials sensitive to frost (maximum -5°C) and are therefore often grown as annuals in our climate. To keep them year to year, it is preferable to grow them in pots to overwinter in a frost-free room or greenhouse and bring them out again in the growing season.

Mimulus ringens

Mimulus is best grown in sun that is not scorching or in light partial shade in a rich, humus-bearing soil kept fresh to permanently moist.

It thrives in naturalistic gardens or exotic-style gardens around ponds, in garden wet areas, in borders and rockeries that remain cool in summer and even in cool container displays.

By virtue of its medicinal properties, Mimulus guttatus is one of the 38 Bach flowers used in alcoholic maceration to calm fears and help control emotions. Applied as a poultice to minor burns, its leaves soothe. Entirely edible, mimulus absorbs sodium chloride from soil, retaining a salty taste that Native Americans used as a salt substitute.

Main species and varieties

Mimulus is perennial in its natural habitat, but has a reputation for being not very hardy in our climates (-5 °C for the most tender such as M. cupreus; -20 °C for the most cold-resistant species such as Mimulus guttatus, Mimulus luteus, Mimulus ringens and Mimulus cardinalis). In our gardens, it is therefore grown either as an annual or as a perennial.

All appreciate soil that remains cool to even moist, some mimulus such as Mimulus luteus tolerating even shallow immersion. They are therefore suited to multiple uses: pond edges, beds, rockeries or containers that stay cool.

Among the 180 species in the genus, Mimulus guttatus or spotted mimulus and Mimulus cupreus, a frost-tender creeping species grown as an annual, are the most widespread. They come in numerous cultivars and hybrids with bright, plain or variegated colours, such as Mimulus x hybridus which offers a wide choice of colourways.

Heights vary from dwarf mimulus (20 cm), well suited to growing in pots, beds and borders, to shrubby mimulus such as Mimulus aurantiacus or orange mimulus, which can reach 1.20 m in height.

Most popular

Mimulus ringens

Beautiful, very hardy perennial mimulus. Its heavenly-blue flowering will illuminate pond edges.

• Flowering time July to October
• Height at maturity 70 cm

See the product sheet

Mimulus Highland Yellow

A lovely hybrid variety, very showy but fairly tender to grow as an annual north of the Loire. A spreading groundcover plant perfect for covering pond edges or flowering for almost six months on pond banks, in a rockery or the front of a cool bed.

• Flowering time July to October
• Height at maturity 20 cm

See the product sheet

Our favourites

Mimulus luteus

A vigorous, hardy groundcover species! It thrives near water and flowers for nearly six months!

• Flowering time July to October
• Height at maturity 80 cm

See the product sheet

Mimulus hybridus Maximus Mixed

A selection of frost-tender mimulus producing giant flowers in a wide range of colours. Ideal in the foreground of borders, beds or pond edges and why not in an exotic garden!

• Flowering time July to October
• Height at maturity 60 cm

See the product sheet

Mimulus Monkey Magic F1 Seeds - Monkey flower

A mimulus grown as an annual with white flowers maculate with blood-red. Ideal for an exotic garden or pond edge.

• Flowering time July to October
• Height at maturity 25 cm

See the product sheet

Planting

Where to plant Mimulus?

Hardiness varies among Mimulus: some are frost-tender down to -5°C, others are hardy to -20°C, for example Mimulus ringens! Most tender Mimulus are grown as annuals in our climate, either planted in ground or kept in a bucket and overwintered in warmth.

It needs a sunny but not scorching exposure to flower abundantly. In southern France, it prefers partial shade.

Very easy to grow, it must never lack water! Perennial of wet mediums, Mimulus particularly enjoys cool, marshy areas. Give it fresh to very wet, light, well-drained and humus-bearing soil. It adapts to many situations, managing to develop where few plants grow. Undemanding, it tolerates any good garden soil that is not too dry in summer, while avoiding stagnant moisture. It will have more difficulty acclimatising to Mediterranean climate, which is too dry in summer.

That said, cultural conditions can vary considerably from one Mimulus to another. While Mimulus luteus tolerates shallow immersion up to 10 cm depth, Mimulus cardinalis endures flooded soils; Mimulus aurantiacus is an exception, intolerant of excess water, more tolerant of drought and preferring a light, well-drained soil. Mimulus cupreus is a dwarf species sometimes used in aquaria.

Mimulus will thrive almost anywhere in the wet ground of a natural garden or exotic garden, provided the location stays cool. Its exotic flowering will be striking in the foreground of cool border beds, in rock gardens and even in a pot. Mat-forming species will make excellent groundcover to scallop pond edges or creep along wet banks where they will find all the moisture they need.

Mimulus lewisii

When to plant?

Plant Mimulus in bucket from March to May when risks of severe frosts have passed, or from September to November after the intense heat.

How to plant?

In open ground

Plant 3 to 5 plants per m² spaced 20 to 50 cm apart. If your soil is too dry, choose a much less thirsty plant.

• Dig a hole 2 to 3 times wider than the bucket
• In very poor soil, add some well-rotted compost or composted manure to the bottom of the hole
• Place the rootball and backfill
• Firm soil then water generously
• Keep soil around the base cool with an organic mulch

In pots

Growing Mimulus in pots is perfectly possible provided rootballs are kept moist in both summer and winter.

• Spread a good layer of drainage (gravel or clay balls) at the bottom of the pot
• Plant in a mix of garden soil, turf, sand and compost, kept consistently moist
• Mulch and water very regularly, never allowing substrate to dry out
• Fertilise regularly with an organic fertiliser during the flowering period

When and how to sow Mimulus?

Sow the seeds of mimulus in seed trays in spring from March to May for transplanting into open ground when risk of frost has passed.

• Sow in trays on surface of a good compost for sowing
• Do not bury seeds
• Keep warm and in light between 20 and 30°C
• Keep moist until germination (10 to 21 days)
• When young shoots have 5 leaves, prick out into buckets
• Plant out in ground or pots after any risk of frost has passed

Seed capsules of Mimulus

Follow our tips to succeed with your seed sowing!

Caring for monkey-flowers

Mimulus needs little attention provided soil remains sufficiently moist.

To flower abundantly, in pots as well as in ground, it needs plenty of water, especially during prolonged drought: water very regularly.

Mulch in summer to retain moisture at the base and reduce waterings.

In case of severe heat and lack of water, flowering may stop: cut the clump back to one-third or half its height to encourage it to flower again.

Fertilise every year in March with compost and apply a fertiliser for flowering plants monthly to mimulus in pots.

Pinch young shoots at the start of growth to encourage plant to ramify.

Remove faded flowers regularly to prolong flowering.

In regions with mild winters, after flowering prune dried parts then spread a mulch of dead leaves at the base to protect stumps from frost. At the very start of spring, tidy the clumps.

In cold regions, mimulus perish with frost: before winter, uproot clumps.

If you nevertheless wish to keep your mimulus for several summers, store pots over winter, keep them well warm and frost-free so you can bring them out the following spring. Cut back the clump, mulch and continue watering even in winter.

Diseases and potential pests

Snails and slugs love young foliage of mimulus at the start of the growing season: we provide tips for controlling gastropods!

Not very prone to disease, mimulus is really only susceptible to powdery mildew, especially during prolonged drought. As a preventive measure to stop this harmless fungus leaving a powdery white coating on the foliage: spray with Bordeaux mixture or nettle and horsetail manure. You will find how to prevent and treat powdery mildew on our blog.

Propagation: cutting and division

When soil suits it, Mimulus self-seeds readily. However, it is a tender short-lived perennial that benefits from winter protection, although some species survive fairly mild winters. Mimulus propagates by sowing, by stem cutting or by division of clumps in spring, in March–April. Sowing is easy (follow our tips above!) with our Mimulus seeds.

How to take stem cuttings of Mimulus?

They root easily in water.

1. In spring, take 10 cm long non-flowering stem tips
2. Remove lower leaves
3. Place in jars filled with water until the cutting forms roots
4. Pot up the cuttings into buckets
5. In autumn, plant them out in garden

Division

1. Using a spade, gently separate divisions from well-established clumps that have sufficient roots and some leaves
2. Replant immediately in garden or in pots
3. Water to encourage root establishment

Companion plants for Mimulus

Mimulus invests the naturalistic gardens to brighten the edges of water features and cool, damp areas. It is unrivalled for contributing to naturalistic atmospheres.

An idea for planting in damp shade: Lysimachia punctata, Hosta, Rodgersia aesculifolia ‘Irish Bronze’, Mimulus (‘Highland Yellow’ for example) , Primula florindae and Dryopteris wallichiana

With its bushy or creeping habit, it allows many uses and combinations.

At the edge of a water feature, it will companion other perennials for damp banks, which, like it, enjoy cool soils such as Japanese irises, spiralled rushes, persicarias or marsh euphorbias, alchemillas, artemisia, variegated calamus, golden lamiums or even mint amid masses of refreshing green foliage.

In a damp, misty and elegant setting, plant it at the feet of astilbes, goat’s beard, and Filipendula, which will provide welcome shade without masking it.

At the edge of a cool, romantic-style border, pair pale-yellow or blue-flowering mimulus with oblique lungwort, Japanese primroses, loosestrifes and Japanese anemones.

The colourful, mottled trumpets of hybrid mimulus such as ‘Monkey Magic’ F1 Hybrid’ or ‘Calypso F1’ will even find a place in an exotic garden (provided plant never lacks water), alongside luxuriant broad-leaved perennials such as cannas, rodgersias, Colocasia madeira, gunneras and hostas.

Another planting idea: Imperata cylindrica ‘Red Baron’ and Mimulus (M. tilingii for example)

Warm tones of spotted Mimulus (Mimulus guttatus), scarlet Mimulus and Mimulus luteus will echo crocosmias and daylilies.

The pastel flowering of Mimulus ringens or “blue Mimulus” will provide a pretty contrast with acid-yellow flowers of marsh euphorbias, Ligularias and Lysimachias, or harmonise with pale violet of Siberian or Japanese irises.

Mimulus will form colourful groundcover in a grass border, surrounded by carex, molinia or miscanthus.