Althea, a fantastic hibiscus

From midsummer right through to late autumn, althea (Hibiscus syriacus) renews an opulent succession of flowers on a deciduous shrub that works as a hedge, in a flower bed, standing alone, or in a pot on a terrace. Give it full sun, sheltered from stronger winds, and the display returns year after year.

Althea at a glance

Name	Hibiscus syriacus
Family	Malvaceae (mallow family)
Type	shrub
Height	3 to 13 feet (1 to 4 m)
Exposure	full sun, part sun
Foliage	deciduous
Flowering	midsummer to late autumn

Caring for this plant, from planting to blooming and including watering and pruning, is easy and this will give your althea magnificent flowers.

Planting althea

Whether you plant it in a pot on a terrace, deck or balcony, or directly in the ground in a shrub and flower bed, Althea deserves particular care upon planting to ensure it grows and blooms well.

Planting althea in pots

All year round, the shrub must be planted in a soil mix designed for flowering plants, for planting, or any universal soil mix.

• Althea needs a pot that is large enough, this will enable it to grow well as seasons come and go.
• A bed of gravel or clay balls at the bottom of the pot will guarantee sufficient drainage. This helps prevent roots from wallowing in sitting water at the bottom of the pot.
• The pot must have a hole at the bottom for excess water to drain away.
• Repot in spring, at least every second year (3 years is also fine occasionally), in a pot that is slightly larger than the previous.

Planting althea in the open

Prefer planting in fall or spring if you have purchased the shrub in a pot or a container.

• Choose a sun-bathed area, sheltered from stronger winds.
• Watering often during the first year after planting is important for Althea.
• Follow our advice on planting shrubs.

Propagating althea through cuttings

Cuttings are very easy to perform in spring for althea.

Simply keep cut stems in a vase with water, and plant as soon as a few roots appear.

Pruning althea

When to prune Althea

At the beginning of spring, towards late winter to early spring, it is time to prune your althea. Early spring pruning still gives the shrub time to produce flowers in the summer of that same year.

Althea blooms on new growth, so you can prune every year.

However, try to avoid pruning late in the season, since this would tend to reduce blooming.

How to prune Althea shrubs

• Remove all branches that grow inwards so that the shrub can filter light through the inside.
• After that, cut remaining stems back by about ⅔, just above an outward-facing bud. This means 1/3^rd of the branch remains on the tree.

Choosing an althea variety

Nearly all garden altheas are cultivars of Hibiscus syriacus, and they differ mainly in flower colour, flower form and eventual size. The table below gathers the varieties most often found on garden centre benches, to help you match one to your bed, hedge or patio pot.

Reading the symptoms on an althea

Most althea troubles come down to water, heat or sap-sucking insects. Match what you see on the shrub to the cause before you reach for the watering can.

Repeated wilting in the same spot is a sign the planting site itself is too hot and dry.

Diseases and pests that attack Althea

Wilting leaves

In hot weather, Althea leaves quickly lose their firmness and start drooping over.

• This is a sign that the shrub needs watering.
• Water abundantly with rainwater.
• Ensure the soil drains well, though, since even in warm weather, wet soil will lead roots to rot.

If this occurs very often, then you’ve planted the shrub in a spot that is too hot and dry for it. Try protecting it with a taller neighboring plant, moving it to a cooler spot, or use a shade veil that dampens the sun out during the hottest hours.

All the leaves drop off within a few days

This, on the other hand, is due to excess water.

• Don’t water until the soil surface feels dry to the touch.
• If it’s still moist, cool, and rather on the sticky side instead of feeling dusty, don’t water yet.

Flowers are stunted, teeming with insects, and are covered in a sticky mess

This is typically due to aphids and to their shepherds, ants.

• Remove aphids from your Althea with these tips

If the bugs look like tiny wisps of cotton, then it’s certainly mealybugs.

Flower buds drop before opening up

Dry air is what causes flower buds to drop before opening up. If in a pot indoors, avoid setting the plant near a radiator or large, sun-filled window.

• Try one of these many ways to increase air humidity around potted plants.

All there is to know about althea

Althea, also part of the Mallow family, is very certainly one of the most beautiful flowering shrubs. Not only is it well suited to any garden, but it also does great on terraces and balconies. Another name for this plant is tree mallow.

Even if this shrub prefers warm climates, several varieties are perfectly adapted to our harsher climates, like Hibiscus rosa sinensis or Hibiscus syriacus.

The numerous cultivars available in garden stores and county fairs allow for many shapes and colors, and each is more beautiful than the next.

Whatever the configuration – hedge, flower bed or stand-alone – althea will enchant you with the beauty of their flowers.

Its blooming is very generous, in that it is both opulent and constantly renews itself from midsummer to mid-autumn and even late autumn if the weather stays mild.

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