Perennials throughout the year

Planting perennials and other herbaceous plants

You can choose from a fabulous range of potted perennials. If you want to put together an arrangement of plants, you can set them out in their pots first in order to assess the effect. For a natural look try creating groups of the same variety. For a more high tech look set them out in ordered groups/rows. 

Steps for planting:

1. Remove the plant from its pot
2. Dig a planting hole
3. Place the rootball in it
4. Press the soil onto if carefully with both hands
5. It is important that the roots are in close contact with the soil
6. Then water thoroughly

Spring tips

Place supports beside tall perennials early in the season in order to prevent them from hanging over smaller plants or being snapped by the wind. Best done when the plants begin to shoot.

Most perennials need to be ‘tidied up’ in the spring (from the beginning of March).
To do this:

• Cut off all the dead stems and remove the dead foliage. Ensure that you do not damage the new shoots. Hedge-clippers are an ideal tool for this. 
• Evergreen perennials which still look good can be left alone, but if they are ugly you can also cut these varieties off just above ground level. They will then grow back attractive and healthy. 
• If a plant is still not doing well by May it is probably dead and is best replaced. 
• Some clump-forming perennials can age. They will then no longer grow or flower very well. The same applies to them.

Summer tips

A number of varieties such as Salvia, Nepeta, Trollius and lady’s mantel (Alchemilla), can be drastically pruned after their flowering has peaked, which will offer the benefit of a second flowering.

As long as perennials have enough water and food, they will do well. If any of these vital ingredients are missing, they will soon show it:  a lack of water can lead to a shorter flowering period and smaller plants, or a lack of food can cause smaller flowers and the plants no longer grow well.

Some plants may also become more prone to pests and diseases. In most cases this involves fungi, such as powdery and downy mildew. Some varieties such as tall phloxes, Aster and Monardas are very prone to this, although an increasing number of cultivars of these varieties are being offered which are less susceptible.

If this happens, cut away the affected parts and dispose of them (in the garden waste bin). Then give the plants organic fertiliser and water regularly. Replace an affected plant or one which sickens repeatedly with a stronger variety. This is more environmentally-friendly that repeated spraying.

During the growing season you can give the most profusely growing and flowering plants, such as Lavatera, some extra organic fertiliser. The others do not need this help if you have provided sufficient long-term fertilisers and a layer of compost (see under winter). 

Autumn tips

Perennials require quite a lot of maintenance in the autumn.

Cut stems which have finished flowering and are very ugly right back if necessary and protect those varieties which are not entirely hardy. For example, lay a layer of conifer branches on the soil close to the roots, or scatter potting compost between the plants.

You should leave dying stems and foliage on perennials as much as possible in the autumn in order to prevent the frost from causing damage later.

Only where the dead plant material could suffocate evergreens should you cut the plants right back, but then compensate by scattering potting soil around the roots.

Winter tips

What about planting some true winter-flowering plants? Look out for lovely Helleborus niger, the Christmas rose, its colourful flowers appear midway through the winter and for many cultivars, continue to flower until the beginning of spring.
 
For non-winter perennials it is a good idea to tidy them up for the winter.  Cut away dead stems. On a number of varieties there is no foliage left by the autumn. Hostas for example, disappear completely. So you do not need to do anything to them.

Placing a layer of compost, (approx 3cm deep), around the perennials annually during the winter period is enough to enable them to grow and flower for many months from springtime onwards. You could also scatter some dry cow manure or bone meal.