Peter Dowdall: Winter quarters beckon for frost-tender plants 

You’re taking a gamble by allowing frost-tender plants remain the ground at this time of year

Frost-tender perennials like this dahlia should be lifted from the ground and brought in for the winter months. Picture: iStock

The October garden requires a bit of work. You’ll discover you need to take up many plants — these could be plants that need a break or that may have passed their best — and fresh new specimens will need to be planted. I guess it’s a bit like Dáil Éireann at election time.

You’re taking a gamble now with anything frost-tender by leaving them in the ground at this time of the year and the odds lengthen with each day as nighttime temperatures dip and the risk of an early frost increases.

Such tender specimens as canna, datura, argyranthemum, gazania and arctotis, to name a few, should be lifted out of the ground and brought inside in pots to spend the winter months in the covered comfort of a glasshouse, polytunnel or even a bright garden shed. A covered carport will do, provided no frost gets in there.

If these plants are growing in pots outdoors during the summer, then this is a relatively easy task, provided you have a suitable covered area into which to bring them. If they are growing in the ground, it may be more difficult and you may even take the risk and leave them outdoors for the winter.

If this is the case then I would suggest keeping a roll of horticultural fleece to hand.

This is a breathable material which protects the plants beneath from the frost. Simply cover the plants with this fleece during the most at-risk periods and remove it when the day has warmed up.

It’s important that you use a breathable material such as fleece as using a plastic material or polythene will not do.

Plastic isn’t breathable and thus condensation will build up inside and this in itself will lead to problems such as the development of fungal infections.

Dahlias. File picture

Dahlias, which are still giving their best in many gardens, are an example of another plant which, if we lived by the textbook, we would all lift and bring in for the winter. I used to refer to my 10 or 20 years of experience in the garden when offering advice; now as that number is growing ever larger, I prefer to say “in my experience in the garden”! 

Well, in my experience in the garden, I have never once lifted a dahlia tuber to be stored inside for the winter. I have often lifted them to divide them into more plants but never to protect them from low temperatures and to the best of my recollection, I have never lost any either.

The one thing that dahlias will struggle with, is the amount of winter rain that we get here. They don’t like to be sitting in waterlogged soil for any length of time so make sure that you plant them in a sunny position in free-draining soil. It helps to include a good amount of grit in the planting area before placing the tubers as this will draw moisture away from the root zone.

Other perennials which may be frost-tender, intolerant of our high rainfall levels, or simply short-lived include diascia, penstemon, some of the verbenas, osteospermums, fuchsias and pelargoniums. These can all be propagated from cuttings taken during the summer and even cuttings taken now, will most likely produce roots if kept indoors. 

This is not only a good way to bulk up on plant numbers but it will also provide insurance in case anything happens to the parent plant left outside during the winter.

They were called “slips” in our parents’ day but to put the correct terminology on it, these plants are grown using semi-ripe, nodal cuttings. This means that the cuttings are of this year’s growth with the base of the cutting being at a node, where a leaf meets a stem. 

The nodes are the magical parts of the plant, where all the hormones hang out and congregate including auxin. This is the hormone needed for a cutting to produce roots and it is at the nodes where you will find the highest concentration of auxin.

Verbena bonariensis.

Take a 10cm-15cm cutting from this year’s growth, making sure that there is a node at the base, remove the terminal bud (which is simply the growing tip) and any signs of buds or flowers as you don’t want any energy going into flower production, you want all the reserves in the cutting to go into root production.

Dip the base of the cutting into some rooting powder or gel, stick the cutting in a small pot or seed tray filled with compost, keep indoors and within a few short weeks you can expect some root development.

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