The move from Summer into Autumn is happening as the days become shorter. Now is a good time to start planning for the spring garden. Order spring bulbs as planting them can start in late September. Hopefully if you have grown vegetables, you should be harvesting them now.
Dividing Perennials
Dividing perennials regularly will ensure healthy, vigorous plants that will perform year after year. It also offers the opportunity to multiply your plants.
Perennials are any plant living for at least three years. The term is also commonly used for herbaceous perennials which grow for many years (To compare: annual = one year, biennial = two years).
Perennials benefit from division every two to three years to maintain health and vigour. If you want to increase the number of plants you have by dividing them, the task can be done more regularly.
When to divide perennials
Plants can be divided successfully at almost any time if they are kept well-watered afterwards. However, division is most successful when the plants are not actively growing.
- Divide summer-flowering plants in spring (Mar-May) or autumn (Sep-Nov) when the soil is dry enough to work. In wet autumns, delay until spring. Spring is also better suited to plants that are tender
- Many spring-flowering plants, such as irises, are best divided in summer (Jun-Aug) after flowering when they produce new roots
How to divide perennials
Here are our simple tips for dividing but do please check a gardening book or the labels on plants before starting this process.
These are just a few examples of plants that can be divided:
Agapanthus, Anemone, Aster, Bergenia (elephant’s ears), Convallaria (lily-of-the-valley) , Delphinium, Epimedium, Eryngium (seaholly), Euphorbia, Geranium, Helianthus, Hosta, ornamental grasses, Primula (primrose), Ranunculus (buttercup), Salvia, Sedum, Verbena, arum lily.
Verbena Bonariensis and Rudbeckia
- Some plants, such as Ajuga (bugle), produce individual plantlets which can simply be teased out and replanted
- Small, fibrous-rooted plants such as Heuchera, Hosta and Epimedium can be lifted and pulled apart gently. This should produce small clumps for replanting
- Large, fibrous-rooted perennials, such as Hemerocallis (daylily), require two garden forks inserted into the crown back-to-back. Use these as levers to loosen and break the root mass into two sections. Further division can then take place
- Plants with woody crowns such as Helleborus or fleshy roots such as Delphinium require cutting with a spade or knife. Aim to produce clumps containing three to five healthy shoots
Aftercare
Plant as soon after division and water them well. They can either be replanted in the same spot, taking the opportunity to mix in a little garden compost.
Perennials needing different methods
Here are three plants that require a different method of division.
Crocosmia and Dierama
Crocosmia
- Divide Crocosmia and Dierama in spring
- To remove the corms without damage, dig down 30cm (1ft) to avoid and gently lift
- The roots of both perennials form ‘chains’ of corms, which can be replanted intact or individually separated. There is evidence that maintaining the ‘chains’ intact may be the better option
- Discard wizened or diseased corms and trim old leaves
- Replant sections at their original depth
It is worth noting that crocosmias flower profusely when crowded, so do not divide clumps too often – every two or three years should be enough.
Dieramas dislike disturbance and will take time to flower again after division.
Hostas
Hostas
- Lift and divide clumps of hostas in spring or late autumn
- Hostas with tough, fibrous roots can be divided with a sharp spade, slicing the clump in two
- Large clumps can be split further to leave sections containing five or six shoots
- Cultivars with loose, fleshy roots are best teased apart by hand or with two hand tools by placing them back-to-back to lever them in two
- Plant the divided sections at their original depth, with the shoots above the soil surface
Ensure that plants don’t dry out while they do re-establish, and check slugs and snails are not attacking your plants.
When to plant bulbs
Autumn
- Plant spring-flowering bulbs including daffodils, tulips, crocus and hyacinths, preferably by the end of September
- Plant tulips in November or even up to mid-December
- Plant hardy summer-flowering bulbs, such as lilies, alliums and crocosmia, in September and October
Planting tulip bulbs
Most hardy bulbs, including tulips and daffodils, prefer a warm, sunny site with good drainage as they come from areas with dry summer climates
Snowdrops and scillas, are some of the earliest flowering plants in the garden, brightening up the short days of very early spring.
How to plant bulbs
Bulbs need specific siting, most hardy bulbs, including tulips and daffodils, prefer a warm, sunny site with good drainage as they come from areas with dry summer climates
Plant as soon as possible. Aim to plant in groups of at least six, as the more bulbs that are grouped together, the better the display. Typically, 25 to 50 bulbs may be needed to make an impressive show.
- Dig a hole wide and deep enough for your bulbs. Plant most bulbs at two to three times their depth. For example, for a bulb measuring 5cm (2in) high, dig a hole 10-15cm (4-6in) deep and sit the bulb in the bottom of it
- Place the bulbs in the hole with their ‘nose’, or shoot, facing upwards. Space them at least twice the bulb’s own width apart
- Replace the soil and gently firm with the back of a rake. Avoid treading on the soil as this can damage the bulbs
- If the ground is moist or the bulbs are autumn-planted, watering is not critical. Otherwise water straight after planting
Bulbs in containers
Most bulbs are ideal for growing in containers, but this especially suits those with large, showy flowers, such as tulips, arum lilies and alliums. For bulbs that are only going to spend one season in their container, use a mix of three parts multi-purpose compost and one part grit. Plant bulbs at 3 times their depth and one bulb width apart.
Pond care
If you are fortunate enough to have a pond in your garden which will be a wonderful magnet for wildlife. Occasional maintenance will help to keep it in good condition.
Remove dead, or fading leaves, so they don’t decompose in the water. Cut back vigorous plant growth – aim to keep half the surface clear. Ensure water is well oxygenated by aerating it and agitating it and using aquatic plants.
Consider cleaning the pond out if silted up or overgrown.
Water is our most precious resource.
Rainwater is better for your plants as it often has a lower pH. Please consider collecting water. Rainwater can be collected from the roofs of homes, garages, greenhouses and other garden structures as long as they have gutters and a down pipe that enters the drain at ground level.
Position the rainwater butt in the shade if you can, as the water will be kept cooler, reducing the growth of bacteria. It is advisable to clean water butts out annually.