Althea, a fantastic hibiscus

Pink double althea flower with crimson red center.

Althea, also called Hibiscus or Rose of Sharon, is a very decorative shrub.

A list of Althea facts

NameHibiscus syriacus
Family – Malvaceae (mallow family)
Type – shrub

Height – 3 to 13 feet (1 to 4 m)
Exposure – full sun, part sun
Foliage – deciduous
Flowering – July to November

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 February-March, 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 1/3rd of the branch remains on the tree.

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.

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.

All there is to know about althea

Althea grows into nice hardy shrubs.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 July to October and even November if the weather stays mild.

Smart tip about althea

If it freezes in your area, it is highly recommended to winterize your plant with horticultural fleece as early as November!