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Planting, Pruning and Maintaining Perennials

Perennials in the garden
Perennials ensure a beautiful garden scene. They flower in various colours. ©iStock/Martin Wahlborg

When Should You Plant Perennials?

Planting perennials
Plant your perennials in the spring or autumn. The more favourable time of year depends on the type of perennial. ©MSG/Frank Schuberth; Prod.:Dieke van Dieken

The ideal time to plant perennials is in the spring or autumn. If you place the perennials in the autumn, they can grow in before the spring and then start straight away with intensive growth.

Perennials which flower in the autumn such as asters, chrysanthemums and Japanese anemones as well as damp-sensitive plants such as oriental poppies or peonies are better planted in the spring.

Which Perennials Should You Plant?

Distribute principle, supporting and filler perennials in groups. It looks particularly attractive if they repeat in large plant beds.

Plant an uneven number of principle perennials, three or five plants. Plant the supporting perennials in larger tufts around the principle perennials. Sage, daises, or yarrow are suitable for this. Lady’s mantel or geraniums look good in the foreground. Their foliage looks neat for a long time. These plants also conceal the edges of beds.

Don’t only choose a perennial for its flowers, but also consider the overall appearance. Sometimes the flower shape and colour are appealing, but the leaves less so.

Last but not least, the flowering period is decisive. Don’t choose plants which flower when you take your annual holiday.

Perennials in the garden
It’s not only the flowers of perennials that are important. Consider the overall appearance of the plant as well when making your decision. ©MSG/Alexandra Ichters

Perennials look best if you plant them according to their size. Place the large perennials in the background and the lower ones at the front in the bed. Plant the medium sized species in between. But don’t stagger the heights too precisely, rather offset the plants. This makes the bed look particularly vibrant.

What Is the Proper Arrangement for Perennials?

Perennials look best if you plant them according to size. Place the large perennials in the background and the lower ones at the front in the bed. Plant the medium sized species in between. But don’t stagger the heights too precisely, rather offset the plants. This makes the bed look particularly vibrant.

The Proper Location for Perennials

Perennials have different requirements of their location depending on the species. The light, the soil quality and the availability of nutrients in the soil are all decisive for whether a perennial develops well or not.

Place shade-loving perennials in darker locations in you garden. These include begonias, barrenwort, hostas and foam flowers. Geraniums, fox gloves, astilbe and bugles are all happy in semi-shade.

Some perennials only develop on dry gravel beds or in prairie gardens. They need lots of sun but very few nutrients. These include Turkish sage as well as stonecrop, mullein and Valerian.

Statement perennials need sun, good soil, regular fertiliser and plenty of water. These include larkspur, aster, day lily, scarlet beebalm, and phlox.

Prepare the Soil for Perennials

Preparing the soil for perennials
Loosen the soil before planting the perennials. Remove weeds in the process. ©iStock/sever180

Before you plant perennials you should carefully loosen the soil. Remove weed roots in the process. The task is easily done with a digging fork.

If the soil quality is not ideal for perennials you can improve the quality. Here’s how:

  • Sandy soils
    If you want to plant bed or shady perennials here, enrich the earth with to 0.5 kg to 1 kg of clay powder per square metre. You can also use well decomposed compost to improve the soil quality.
  • Loamy soils
    Make loamy soils more permeable for winter-hardy perennials with leaf compost. Underpinning with sand can also help here.
    Rock garden and steppe perennials grow better in loamy soils if you work in 10 l to 20 l of rough grit per square metre.

In general, horn shavings can improve the soil for perennials. Use 100 g for every square metre for perennial beds. You can use just 50 g per square metre for other perennials. You can also improve the top soil layer with basal rock dust. Use 100 g of this per square metre.

Planting Perennials: Step by Step

Simply follow our instructions for planting perennials step by step to ensure that your perennials grow well and develop quickly.

1. Water and Position the Perennials

Submerge the root ball of the perennial in a bucket of water. Leave it in the water until no more bubbles emerge. Then distribute the pots in the bed at the correct distance.

Perennials in a bucket
Water the perennials before planting. The root ball should be completely saturated. ©MSG/Martin Staffler

2. Planting perennials

If the plant arrangement looks good, carefully remove the perennials from their pots. Try not to damage the roots in the process. If the perennial growth has become attached to the pot, cut off the affected roots with secateurs.

Then dig the planting hole. It should be about twice the size of the root ball. Use the root ball as a depth guide. After planting it should be the same height as the surrounding soil.

3. Fill in the soil and press down

Then return the dug up earth to the plant holes and press down firmly. Follow this with plenty of water.

Planting a perennial
Place the earth from the planting hole on the plant and press in firmly. Then give the perennial plenty of water. ©MSG/Martin Staffler

Caring for Perennials

After planting the perennial you will need to care for it. This will help them develop well and adorn your garden with beautiful flowers.

Watering Perennials

Take extra care in the weeks after planting to ensure that the soil never dries out. The roots of the young plant are not yet long enough to draw water from the deeper layers of the ground.

Water your perennials in the morning. This is the time when the soil can absorb water particularly well. Water generously. This will enable the plants to grow long roots. This will enable them to withstand upcoming dry spells much more easily. The shower mode of the Fontus from the Bosch 18 volt battery system is suitable for gentle watering.

The frequency for watering depends on the weather. The species of perennial is also decisive. Coneflower and desert candles require less watering. The Siberian iris and bonesets have a higher water requirement. Perennials in semi-shade such as the false goat’s beard or masterworts do not tolerate dryness. Never let root balls from these species dry out.

Watering Perennials
The frequency which with you should water your perennials depends on the weather. However, the species of perennial is also decisive. ©MSG/Martin Staffler

Fertilising Perennials

You should not fertilise perennials in the first year. Otherwise their roots won’t grow as intensively as they can get all their nutrients from closer by.

Afterwards, fertilise your perennials carefully. Lots of nutrients will ensure active growth. However, the leaf tissue will then often also be weak. This makes the plants more susceptible to mildew and other fungal diseases.

Mature compost is sufficient to supply most perennials well for the coming year. Distribute a thin layer of this over the entire bed in good time in the spring, so before they start growing shoots. You can find out how to make compost here.

Flowering perennials such as the larkspur or phlox require more nutrients. Give them additional horn meal or organic complete fertiliser in the spring. Alternatively, use a mineral fertilizer in the early summer.

Fertilise evergreen perennials in the autumn with a special, potassium-rich fertiliser. This will help the leaves to tolerate frost more readily and they will not turn brown so quickly.

Supporting Perennials

Perennials with very large flowers should be supported with a rod. Bamboo is very suitable for tall perennials. Alternatively, you can use a supporting ring for your plants. This is suitable for oriental poppies, heliopsis and yarrows, for example.

Pruning Perennials

Pruning Perennials
It is preferable to prune your perennials in the summer. Then the plants may flower a further time in late summer.

Regular pruning is good for your perennials. You can prune them practically all year round. However, pruning in the summer is particularly recommended, as sometimes the perennial will then flower second time in late summer.

For a second flowering, cut the entire perennial to a hand width above the soil as soon as most of the flowers have faded. Pruning is particularly easy with power-assisted secateurs such as the Easy Prune from Bosch or with a hedge trimmer. You can cleanly, quickly and safely trim several shoots at the same time with the EasyHedgeCut 18-45 hedge trimmer from Bosch.

Then fertilise the perennials and give them plenty of water. After four to eight weeks they should flower again.

Extending Perennial Flowering Periods

Some perennials flower at staggered intervals, i.e. in several stages one after another. You can extend the flowering periods of these varieties. For this, simply pluck out all the withered stems. This prevents the perennials from forming seeds. Instead they develop new stems.

Extending the Lifetime of Perennials

Flowering Perennials
Prune the perennials back before they form seeds. In this way you can extend the lifetime of the plants. ©MSG/Silke Blumenstein

Some species of perennial should be pruned in the planting year even before they flower. In this way you can strengthen the plant and extend its lifetime by a few years.

In the next season, you then wait for the flowering to finish and only prune back the perennial before it starts forming seeds. With the following species, for example, you can extend the lifetime with this kind of pruning: hollyhock, hesperis, horned violet, blanket flowers and white gaura.

Prevent the Perennials from Self-Sowing

You can also stop self-sowing in perennials with a single cut. Perennials form lots of seeds which readily germinate in the garden soil. If you don’t do something to prevent this, you will soon have an extremely dense crop of perennials in the garden. This often simply displaces competing plants.

You can prevent self-sowing. Do this by simply cutting off the stems of these perennial species before the seeds mature: false goat’s beard, purple loosestrife, solidago, lady’s mantle, red yarrow, phlox, Jacob’s ladder, clustered bellflower, spiderwort and mourning widow.

Planting, Pruning and Maintaining Perennials
Perennials ensure fresh colour in your garden. With the proper care you can enjoy many years of joy from them. We can tell you what you need to know about planting, pruning and caring for perennials.