Q. What are herbaceous perennials?

These are plants that normally grow from below soil level during the spring.

In summer and autumn they produce leaves, flowers, and sometimes fruit.

They then die down below ground level during winter to re-emerge in the spring to start the cycle all over again. 

The new growth of the season is already emerging by March so old growth can be cut back.

Where the old growth doesn’t pull away from the plant easily, chop this down with shears or if there is a danger or damaging the new growth, use secateurs.

Ornamental grasses can be left until last as they hold last year’s growth well without looking too scruffy. Grasses that have died off can be cut down to just above the new shoots. The evergreen grasses can be combed through with a rake to pull out the dead thatch. All the trimmings can be wheeled onto the compost heap using the trusty wheelbarrow.

Q. How can these be divided?

When the weather is dry enough in winter and spring,it’s a good time to divide most perennials, grasses will divide better in summer though.

With a lot of perennials the centres tend to die off if they are not divided as the growth moves out, away from the original plant, which eventually weakens the whole clump.

Perennial clumps can be gently lifted with a fork and the soil shaken off the roots. The youngest sections can be pulled off or cut apart with a knife then replanted.

When the new offshoots are planted take the opportunity to improve the soil by adding compost, manure and a handful of plant food such as blood fish and bone into the planting hole.

 Digging up and dividing perennial plants at this time of year are an ideal opportunity to reposition any you feel are in the wrong place. In my case it’s rare a plant goes into the right place when I first plant them and it generally takes me a few attempts to be totally happy with the result.

Different types of roots

Many herbaceous plants can be divided and by doing so you can have lots of new plants.

Plants with fibrous or roots can easily be lifted and divided, but plants with fleshy or rhizomatous roots need to lifted and divided by using a sharp knife.

Dividing fleshy rooted plants. Dig up the plant and with a sharp knife separate the woody crowns. Make sure that each new piece has strong roots and several bud growths. Again if its an old big clump that's been in the ground for several years or more then throw away the centre part.

Plants with fleshy Crowns include: Delphiniums / Lupins / Astilbe / Hosta.

Fibrous rooted plants:  Dig the plant out of the ground and place two garden forks or hand forks back to back and then lever their handles together. This pulls the plant apart and untangles the roots. You will need to repeat this technique several times to end up with small divisions of the main clump. A golden rule is usually to throw away the centre part of the main clump and keep and replant the outer parts of the plant. The centre of the clump is the older part and becomes woody.

Plants with fibrous roots include: Artemisia, Asters, Golden Rod, Herbaceous Campanulas, Herbaceous Geraniums, Meadowsweet, Perennial Spiraea, Perennial Sunflowers and Yarrow.

Dividing rhizomes:  Dig up and select young outer pieces.

 Use a sharp knife to separate the rhizomes. Select pieces that have at least one or two fans of leaves from the outside of the clump and discard the centre rhizomes.

Plants with rhizome roots include: Flag Iris, Lily of the valley and Orris Root.

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