Perennials: planting / RHS Gardening (2024)

This information relates to planting perennials, including herbaceous perennials. See our

Perennials are planted in beds and borders. These are often mixed borders, where they are grown with trees, shrubs and bulbs. However, herbaceous perennials (that die down in the winter) were traditionally grown on their own in an herbaceous border.

Where to plant

Perennials can grow in every situation in the garden. From shady to sunny, wet to dry soil, there are suitable plants available. However, it is essential to choose the right plant for the location, as they will not thrive without the right conditions.

• To grow the widest range of perennials, site new beds and borders in full sun where there is shelter from wind
• Perennials can be grown in difficult areas, such as dry shade. See our Perennials profile for links to all our pages of relevant information

There is no practical difference between a bed and a border: both are simply defined areas of well-prepared soil containing plants. They are commonly adjacent to paths, lawns and hedges.

Perennials are best planted in spring (March to early May) or autumn (late September to October), while the ground is moist.

Barerooted plants Theseneed to be planted at the optimum times, mentioned above. These are usually bought by mail-order.

Container-grown plants Sold throughout the year at garden centres and nurseries. They can be planted at any time as long as the ground isn’t frozen or waterlogged. Likewise, after planting, they must be kept moist, especially if planted in summer.

Too get worthwhile results, good soil preparation, planting and aftercare is needed. This effort should be rewarded with a display for many years.

Planting bareroot perennials

These plants usually arrive by mail order, but you might also get bareroot clumps from gardening friends.
Begin by assessing the bareroots provided. Good-sized clumps, typically over 7.5cm (3in) across can be planted straight into the border. Smaller clumps and roots are best potted and grown on in a cold frame or sheltered area of the garden before planting out.

1. Begin by preparing the soil. If you are creating a new border, consider double digging otherwise remove the weeds and single dig
2. Arrange the bareroot clumps on the surface so you can see how they will look (see section on Spacing below)
3. Next, use a trowel or spade to create a hole just deep and wide enough to set in the clump. The aim is to bury just the roots, leaving the bases of the stems (when in growth in summer) and/or the shoots (in spring) above ground
4. Firm back around the soil, using your hand for small clumps and your heels on large ones
5. Water in well even if the ground is moist and rain is forecast. This will settle the soil and prevent desiccation

Planting container-grown perennials

This process is similar to bareroot perennials, but has some extra steps.

1. Begin by preparing the soil. If you are creating a new border, consider double digging otherwise remove the weeds and single dig
2. Arrange the container-grown perennials on the surface so you can see how they will look before planting (see section on Spacing below)
3. Individually knock out each plant from its container. Look at the roots – if they are circling around the compost, it is best to tease them out. To do this, push your fingers into the rootball along the bottom edge and pull to rip the roots. Do this in three to four places. This will prevent the roots growing round and round and, therefore, should encourage the roots to spread into the surrounding ground
4. Next use a trowel or spade to create a hole just deep and wide enough to set in the rootball. The aim is to bury just the roots, leaving the bases of the stems (when in growth in summer) or the shoots (in spring) above ground
5. Firm back around the soil, using your hand for small clumps and your heels on large ones
6. Water in well even if the ground is moist and rain is forecast. This will settle the soil and prevent desiccation

Spacing

It is tempting to plant closely to get a quick, full effect from your plants. However, most plants are relatively small when you buy them so it is wise to give them room to grow.

As a general rule, check the plant label and look for the predicted spread or width (check a book or RHS Find a Plant if none is given). This will be the maximum spread, so aim to plant a little closer if you wish for plants to knit together with no soil visible.

So, for example, if a plant has a spread 60cm (2ft) wide, plant about 50cm (18in) apart.

When planted too closely, plants generally perform poorly as this creates competition for light and water. However, with initially small plants, it is possible to plant a little closer for the first few years, but they will then need lifting and dividing to correct their spacing.

In most cases, the key to success with perennials is keep them well watered. This particularly applies in the first year, even if they are described as drought tolerant. Aim to keep the ground moist, but not soggy, using either a watering can or hose. Apply the water under the foliage.

Feeding again after the ground has been prepared isn’t usually necessary, but if plants appear yellow or growth is poor, apply a liquid fertiliser.

Staking will be needed for many taller perennials to prevent them flopping or the flowers from being blown over.

There are few specific problems associated with planting, especially if carried out between autumn and spring. However, ensure that plants don’t dry out while they establish.

It is worth carrying out slug and snail control from February. Likewise, rabbits and voles can be problematic at times.