<em>Mimulus</em>, mimule: planting, 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, the Americas, Mexico, Australia and South Africa. The genus includes about 180 species, annual or perennial, 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 more widespread species together with Mimulus cupreus.

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

Depending on species and cultivars, Mimulus adopts a variable habit; erect, semi-trailing, even trailing or very mat-forming (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 to 1.20 m in height and as wide for shrubby species such as Mimulus aurantiacus.

Although growth is fairly rapid, Mimulus is a short-lived perennial that benefits from regular propagation to persist in the garden; except for hybrid varieties, it readily self-seeds in heavy, wet, clay soils.

Mimulus forms a small shrub most often very mat-forming with deciduous foliage, rarely evergreen in our climates, except for Mimulus aurantiacus, the orange monkey flower.

Mimulus guttatus flowering

Shoots, often pubescent, bear opposite leaves, oblong, rounded or linear, entire, slightly to strongly dentate, sessile in upper parts and petiolate lower on stems. They are sometimes covered with a fine velvet or are sticky. This dense, vigorous foliage, from pale green to grey-green, sometimes first bronze then green, is hidden beneath the long and very generous flowering of Mimulus.

Flowers with intense and varied colours appear in the axil of the leaves. They open from June to September continuously, standing out against the foliage. Stems, erect, semi-erect or prostrate, end in spikes of 3 to 8 trumpet- or funnel-shaped flowers. Enclosed in hairy calyces, they consist of five fused rounded petals; two upper petals turned back above three lower lobes, the central one being larger. These bilabiate corollas with a gaping, hairy throat suggest a smiling mask with tongue protruding, or the grimacing face of a mocking monkey. This shape has earned Mimulus the English name ‘Monkey Flower’.

Flower size varies with varieties and hybrids. They measure from 2 to over 10 cm in diameter for the largest, such as Mimulus x Hybridus ‘Maximus Mixed’, which bears giant flowers on average four times larger than most Mimulus flowers.

The flowers occur in an endless array of vivid single 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 bicoloured varieties, fully marbled or striped, or with the throat subtly flecked in a contrasting colour (spotted Mimulus or Mimulus guttatus, Mimulus x hybridus ‘Monkey Magic’ F1 Hybrid’, ‘Calypso F1’).

If most Mimulus flowers are unscented, some species such as Mimulus moschatus emit a distinctive musky scent, hence the name “musk-flower” sometimes given to the plant.

This endless flowering is melliferous, attracting large numbers of pollinating insects.

Although some hardy Mimulus (down to −15 to −20 °C) can withstand frost, most hybrids are tender perennial plants that tolerate frost only to around −5 °C and are therefore often grown as annuals in our climate. To keep plants from year to year, it is preferable to grow them in pots and overwinter them in a frost-free room or greenhouse, bringing them out in the growing season.

Mimulus ringens

Mimulus is grown in sun that does not scorch or in light partial shade in a well humus-bearing soil that remains fresh to wet.

It likes naturalistic gardens or exotic-style gardens by ponds, in wet garden areas, in borders and rockeries that stay cool in summer and even in cool container displays.

Because of medicinal properties, Mimulus guttatus is one of the 38 Bach Flower remedies, used in an alcoholic maceration to soothe fears and help with emotional control. Applied as a poultice to minor burns, leaves soothe heat. Completely 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-hardy 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 moist, some mimulus such as Mimulus luteus even tolerating shallow immersion. They therefore allow multiple uses, on the banks of a pond as well as in borders, rockeries or cool containers.

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

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

A beautiful, very hardy perennial mimulus. Its sky-blue flowering will brighten the banks of a pond.

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

See the product sheet

Mimulus Highland Yellow

A beautiful, very luminous hybrid variety, though quite tender and best grown as an annual north of the Loire. Groundcover plant perfect for covering pond edges or flowering for almost six months the banks of a pond, a rockery or the front of a cool border.

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

See the product sheet

Our favourites

Mimulus luteus

A hardy, vigorous 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 front of borders 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 is variable among Mimulus: some are frost-tender down to -5°C, others are hardy to -20°C, for example Mimulus ringens! The most frost-tender Mimulus will be grown as annuals in our climates, either in open ground or in a pot to be overwintered in warmth.

It needs sunny but imperatively 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 especially appreciates cool, marshy areas. Offer a cool to very wet, light, well-drained and humus-bearing soil. It nevertheless adapts to many situations, managing to develop where few plants grow. Undemanding, it tolerates any good garden soil not too dry in summer, without stagnant moisture. It will have more difficulty acclimatising to Mediterranean climate, which is too dry in summer.

That said, cultural requirements can vary markedly from one Mimulus to another. While Mimulus luteus tolerates shallow immersion down to 10 cm, Mimulus cardinalis copes with flooded ground, Mimulus aurantiacus is an exception in fearing excess water, being more tolerant of drought and preferring a light, well-drained soil. Mimulus cupreus is a dwarf species sometimes used in aquaria.

Mimulus will be happy almost anywhere in damp areas of a natural garden or exotic garden, provided the spot remains cool. Its exotic flowering is particularly striking in the foreground of cool borders, in rockeries and even in a pot. Spreading species make excellent groundcover to edge ponds or creep over moist banks where they will find all the moisture they need.

Mimulus lewisii

When to plant?

Plant Mimulus in bucket from March to May once risk of severe frosts has passed, or from September to November after high summer heat.

How to plant?

In open ground

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

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

In a pot

Growing Mimulus in a pot is entirely possible provided you keep rootballs moist in summer as well as winter.

• Spread a good layer of drainage (grit or clay balls) at bottom of 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
• Feed regularly with an organic fertiliser during flowering period

When and how to sow mimulus?

Sow mimulus seeds in seed trays in spring from March to May for transplanting outdoors once any risk of frost has passed.

• Sow in trays on surface of good seed compost
• 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 into pots after any risk of frost has passed

Mimulus seed capsules

Follow our tips to succeed with your seed sowing!

Caring for monkey flowers

Mimulus requires little attention provided soil remains sufficiently moist.

For abundant flowering, 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 around the base and reduce watering.

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

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

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 around the base to protect stumps from frost. In early spring, tidy clumps.

In cold regions, mimulus perish in frost: before winter, lift the clumps.

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

Potential diseases and pests

Snails and slugs love young foliage of mimulus when growth begins: we provide tips to control 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 from leaving a white coating on the foliage: spray with Bordeaux mixture or nettle and horsetail manure. You can 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 being made perennial, although some species survive milder winters. Mimulus is propagated by sowing, by stem cutting or by dividing clumps in spring, in March–April. Sowing is easy to do (follow our advice above!) with our mimulus seeds.

How to take stem cuttings of Mimulus?

They are easy to root in water.

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

Division

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

Companion planting with Mimulus

The Mimulus takes to naturalistic gardens to brighten edges of water features and cool, damp areas. It is unmatched at contributing to natural atmospheres.

Planting idea for moist 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 edge of a water feature, it will be companion to other perennials of damp banks, liking cool soils as much as it does: Japanese irises, spiralled rushes, knotweeds or marsh euphorbias, alchemillas, artemisias, variegated calamus, golden dead-nettles or even mint in exuberant displays of refreshing green foliage.

In a humid, misty and elegant setting, plant it at feet of astilbes, goat’s beard and filipendulas, which will provide beneficial shade without hiding it.

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

The colourful, patterned 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), with luxuriant perennials with ample foliage such as cannas, rodgersias, Colocasia ‘Madeira’, gunneras and hostas.

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

Warm-toned flowers of spotted Mimulus (Mimulus guttatus), scarlet mimulus and Mimulus luteus will find echoes among crocosmias and daylilies.

Pastel flowering of Mimulus ringens or “blue mimulus” will offer 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.