Tool Tech: how to reinvigorate your summer perennials by division
Reinvigorate summer perennials by lifting and dividing the crowns, says
CLUMP-forming hardy perennials that grow from a crown of buds and roots are some of the easiest plants to grow and provide a stunning array of flowers. However, if they’re just left in the ground to get on with it, after about five years they can look tatty. Growth becomes irregular as the centre of the plant weakens.
To avoid this, clump-forming perennials (as opposed to shrubby types like fuchsias and lavender that are best propagated from cuttings) should be lifted from the soil every three years, divided into healthy chunks, and replanted in improved soil. If treated in this way they quickly grow back into tidy clumps and flower much better.
When dividing crowns you get at least two healthy chunks to replant. The freebies can be planted elsewhere or given to friends or swapped for plants.
Summer-flowering perennials can be divided in autumn or in spring, but I’m usually much too busy come March or April so I prefer to tackle them now.
Tools needed
Tools you need include a sharp spade and two stout forks. I prefer a small border spade and fork that are lighter and more manoeuvrable, but for big clumps or on heavy soil you may need a full-sized digging spade and fork.
Specialist compact perennial spades are available, such as the Burgon & Ball Perennial Spade (£19.99 from burgonandball.com). This has a very short handle (overall length 21in/53cm) so it’s easy to use while kneeling, and a small head with a pointed tip for slicing through crowns. If you’re feeling confident you can use it to just dig chunks of the plant you’re dividing directly out of the soil, with the roots attached. It’s worth considering if you do a lot of lifting and dividing.
You’ll also need secateurs or shears, a hand trowel and hand fork, a groundsheet on which to divide plants so you don’t make a mess, moistureresistant gardening gloves such as Town & Country Master Gardener gloves ( townandco.com) so your hands don’t get muddy, garden compost or wellrotted manure, and fertiliser to improve the soil before replanting divisions. If you’re going to pot up divisions, seek out some two-litre pots and potting or multi-purpose compost. Finally, you’ll need labels and a pencil/marker.
How to lift
To lift an established perennial crown, first cut down all top growth. Now thrust your garden or border fork in deep, vertically, at the edge of the crown, then ease gently back on the handle to loosen roots. Work around the crown easing it up until you’ve gone all the way around, then with a little more effort the rootball should lift. You want as much root attached to the crown as possible, hence the gentle approach.
Lay the sheeting on a hard surface.
Place the crown and rootball on its side on the sheet, and thrust your fork prongs top-to-bottom through the centre of the crown. Take your second fork and thrust it in back-to-back with the first – this should leave the handles 2-3ft (6090cm) apart. Pull the handles firmly together, which should ease the crown into two pieces with plenty of roots attached to each half. Repeat this process several times if the crown is very large, so you end up with chunks of crown about 8in (20cm) across with roots attached.
Some crowns, such as those on ornamental grasses, are dense and are more easily divided after lifting by using a sharp spade. Do this by laying the crown on its side and carefully slicing top-to-bottom through the centre of the crown, then through the centre of each piece until they are the size you require.
Other crowns such as tulbaghia are loose and can be eased apart with just a hand fork and trowel. Dividing the crown doesn’t work well with lupins, which have a long tap root. Instead, take basal cuttings from the root base in spring.
Improving soil
Improve the soil in the planting site by adding compost or well-rotted manure and fertiliser, then replant a healthylooking chunk of the divided crown. The crown should be at the same level as the soil surface when the roots are well settled. Water it in, and don’t let it dry out for at least a couple of weeks. Plant other divisions elsewhere, or pot them up. And don’t forget to label them!