Divide and conquer in the garden with Peter Dowdall

Knowing when to divide herbaceous plants can be key to a lovely garden, says Peter Dowdall.

Whatever about seeing a few early flowering daffodils which have been visible now since before Christmas, I was dumbfounded recently when I came across an established clump of Alstromeria ‘Indian summer’ in full flower in January.

To put that in context for those who don’t know, this is a herbaceous perennial, it should be lying asleep, dormant under the ground during January. It wasn’t one or two flowers, this was near enough to be in full flower.

Indian summer is a particularly nice, relatively recently introduced cultivar. It is vigorous without being invasive like some of its more, unruly cousins. It grows to a height of about 60cm to 80cm with lovely bright orange/red flowers which contrast beautifully with the chocolate brown foliage. It does need to be staked to prevent the blooms from falling over.

There are varieties of daffodils which will flower as early as December so while many varieties may indeed be flowering a bit early, it’s certainly not that unusual to see some of the cheerful yellow trumpets above ground in January.

Whatever the unseasonably mild weather during December and January was due to, it certainly led to some interesting sights such as this in the garden.

Will it harm plants if we suffer snow or frost before the end of winter?

No, it won’t, as what has happened in the case of this Alstromeria and those like it is that it hasn’t yet gone to sleep after 2018, as it didn’t get cold enough.

It’s still flowering from last year as opposed to it being in flower early for this year. So, with the cold weather just returned, this specimen has curled up under ground and come spring time will break the soil once more in preparation for the season ahead.

Its period of dormancy will be greatly reduced however, and I don’t know what effect, if any that will have if it continues on a longer-term basis. The risk to the plant would be if we get extreme cold or snow, out of season. If, after the plant started its growth for 2019, temperatures plummeted then, some damage would be done, but let’s hope that doesn’t come to pass.

Perennials that have died back for the winter can still be lifted and divided right up to the end of this month. I would even suggest that the same could be done to those that have not yet died back. Cut back the foliage and flower stems to ground level and then lift and divide.

Dividing established clumps of herbaceous has the benefit, obviously of providing the gardener with more plants for free, allowing you to bulk up on favourites but it also benefits the parent plant, by helping to restore its vigour.

Depending on what species you are working with will determine how exactly you divide but for all of them, lift the entire clump out of the ground during this dormant period and identify the crown or growing shoots of the plant.

If the plant grows from a bulb such as a Lilium, or a corm such as Crocosmia, then it’s quite obvious what to do as you will see a cluster of individual bulbs or corms all connected to the one root system.

To divide these, you simply prize the bulbs apart from each other, store them and replant again later in February or March using a good amount of horticultural grit to ensure excess moisture drains away from the bulb.

For tuberous plants such as dahlias and cyclamen, it’s best to use a sharp knife and cut the root system into individual plants ensuring each new clump has at least one ‘eye’ or growing bud.

The same is true for the majority of other perennials such as alstromerias, which grow from rhizomes or fleshy roots. When dividing these, each new plant should have at least two or three fleshy roots attached to a growing shoot.

It may sound a bit like hard work but it really isn’t. The hardest task is lifting the original clump out of the ground.

Once you have made the divisions you can simply grow them on in pots filled with compost and soil or plant directly into the ground. Any cuts made, particularly to tubers could be treated with a light dusting of copper sulphate, a good, organic fungicide to prevent any fungal infection entering through the wound before it calluses over. Then your plants provide your garden with even more flower colour for summers.

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