Horticulture Magazine

How To Divide Alstroemeria Tubers

Lily of the Incas in the botanic gardens of Singapore

Dividing Alstroemeria tubers is an easy garden job.

Like other perennials, Alstroemeria tubers can be divided to reduce overcrowding and propagate new plants.

Read on to learn a little more about this plant and to discover why, when and how to undertake this simple task.

What is Alstroemeria?

purple, pink and yellow alstroemeria flowers

Alstroemeria, also known as Peruvian lily, has long been popular for inclusion in cottage gardens. Excellent in summer borders or containers, there are modern cultivars to choose from which flower for longer, and which have even more impressive blooms.

The vibrant flowers of Alstroemeria resemble lilies. They come in a huge range of different colours and are often striped or speckled with additional hues. With so many different options to choose from, they can fit in with many different styles of gardens.

Alstroemeria plants require a sunny, sheltered site, with a reasonably fertile soil or growing medium which drains easily. They are generally hardy, and the fleshy roots or tubers from which they grow can be left in place over winter.

These are good choices for growing alongside roses, and other traditional cottage garden plants. They are also good for attracting bees and other pollinators to your garden.

Why Divide Alstroemeria Tubers?

There are two main reasons why you should divide Alstroemeria (and other clump-forming perennial plants).

The first reason is to clear space and reduce overcrowding in a bed or border, or to stop a mature plant from outgrowing its container.

The second reason is, of course, to propagate your plant, and obtain new plants for your garden. Propagation by division is the easiest way to get new Alstroemeria plants, since these plants are not easy to grow from seed.

If you collect your own seeds then the plants you grow may not look the same as their parent. Plants grown from seed will also take several years to flower.

When you divide Alstroemeria, you will obtain a number of plants immediately, each of which will be an exact copy of the parent plant. These new plants can also be placed in new containers, or elsewhere in your garden right away.

Dividing plants is a great way to make new plants to fill new areas in your garden and to improve existing growing areas.

When To Divide Alstroemeria Tubers

Alstroemeria tubers are best divided in April, though you may also undertake the task in May.

While other summer flowering plants can often also be divided in autumn, between September and November, this is not the best time to divide Alstroemeria tubers because they can be a little tender.

Also, because the new plants must be planted right away, spring sowing gets them the easiest start.

If your alstroemeria are growing in a bed or border, among other perennial plants, it is best to think about dividing your clumps every 2-3 years or so, even if you are not in need of new plants.

This ensures that the plants remain healthy and flowering well, and will also help to prevent overcrowding in the growing area.

How To Divide Alstroemeria Tubers

A little more care is required when dividing alstroemeria tubers than is required when dividing many other perennial plants. But it is still a relatively easy job.

First: Lift the Plant From the Soil

Alstroemeria have fragile roots and they do not cope well with any damage. So it is very important to be as careful as possible at this stage.

Place a garden fork or spade into the soil at some distance from the base of the plant. Then gently lever to raise the plant out slowly, easing it out of the soil.

Prepare the Root Ball

Now that the root ball is above ground, carefully examine it. Gently knock off excess soil so that you can see the tubers clearly. Again, be very careful not to damage the roots.

You will note that the tubers are tangled together into a clump.

Separate the Tubers

As you examine the root ball, you can now gently begin to disentangle individual tubers from the clump. At this stage, you will have to decide how many new plants you wish to make from this parent plant.

Often, you will be able to simply tease the tubers apart by hand. Occasionally, you may wish to use a sharp knife to separate roots that are particularly enmeshed, though this is not usually required.

Replant as Quickly as Possible

The key thing to remember about Alstroemeria tubers is that, unlike tubers of many other plants, they will not store well. You need to make sure that you replant your divisions as soon as possible, either into containers or a suitable spot in your garden.

Remember, as mentioned above, Alstroemeria require reasonably fertile soil, which is free draining, in a sunny and sheltered spot. If using containers, these should be filled with John Innes No. 2 compost or a homemade equivalent.

Planting Alstroemeria Tubers

pink and yellow Peruvian Lily

Alstroemeria plants should be replanted to the same depth that they were at in the previous location or container.

Simply bury the tubers and leave any shoots sticking up above the surface of the soil or growing medium. Divisions of tubers should be planted to a depth of around 15cm.

Mulching around the plants with organic matter to add fertility, reduce moisture loss and suppress weeds to a degree can be a good idea. However, make sure that the mulch does not actually touch the base of the plants.

The divisions should begin to produce new growth and flowers within 15 weeks. Be patient and do not be tempted to give up on your tubers if you are worried that they are not yet growing.

Wait for at least four months before determining that something has gone wrong.

Keep the area moist but do not overwater. The tubers can rot in damp soil and prolonged waterlogged conditions. Remember that more watering will be required when growing in containers.

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