Mary Keenan’s Garden Diary: break for the border

February is a busy month for us as work in the garden really gets back into full swing. At the moment, borders aren’t looking at their best, but this is the time to get them ready for the growing season ahead.

We start by systematically going through each border, removing weeds and cutting back last season’s dead stems of all the herbaceous perennials down to soil level. The aim is to get all the cutting back done as early as possible to avoid damaging the new growth coming through. All the cut material is then chopped up and added to our compost heap.

Consider division

Most herbaceous perennial plants, such as lupins, hardy geraniums and hostas, benefit from division every three to five years to rejuvenate their vigour and improve flowering. When the cutting back is done, we dig up and divide any old, tired and congested perennial clumps, discard the unproductive central portion and replant the young outer sections. It’s also a good time to move plants and adjust planting combinations that are not working, perhaps because of mismatched height or colour.

We then lightly fork over the bare spaces between plants to relieve surface compaction, break up growth of liverwort and improve drainage. We finish off by spreading a deep mulch (7-10cm) of compost over the surface of the border. Over the coming months, earthworms will work this material down into the soil, enriching it for the season ahead.

Clumps of deciduous grasses, like miscanthus and calamagrostis, that have been left for winter interest, are also cut down now to make way for new growth, but we delay lifting or dividing these until they are actively growing again, which can often be well into April. Evergreen grasses, such as carex and stipa, need nothing more than a good comb through with gloved hands to remove old growth.

Vacant spaces

Where there are vacant spaces in our borders, we will use some of the perennial plant divisions to plant up these gaps, rather than buying new plants. Repeating plants in garden borders is a great way to unify a planting scheme. We like to use multiples of the same plant in drifts for stronger impact, spacing them slightly closer than recommended so that the plants knit together with no soil visible. Dense planting like this helps to shade out and inhibit weed growth.

Get a handle on things

To ensure even spacing when group planting, it can be helpful to use the long handle of your planting spade as a measuring stick. Lay it on the ground alongside a tape measure and use a permanent marker to mark out some common gardening measurements like 15cm, 30cm, 45cm and so on along the handle. When you need to space plants a certain distance apart, you’ll have a ready-made measuring device in your hand.

Several of the show gardens at Bloom last year featured impressive displays of Eremurus or foxtail lilies, which prompted me to buy some for planting in my own garden this spring. Guaranteed to prompt a wow-reaction, these tall, stately perennials feature distinctive, bottle-brush spires of star-shaped flowers in white, pink, pastel peach, brilliant yellow or burnt orange. Blooming from June into July, they make dramatic, long-lasting cut flowers and are attractive to bees.

Foxtail lilies do best in a really warm planting site in full sun. A well-drained, ideally sandy or gritty soil is essential for success. Choose a sheltered position where the tall flowers will be protected from strong winds and give them plenty of space as they don’t do well if crowded.

Bare-root crowns are available for planting from autumn to early spring. I prefer to plant them in spring to minimise risk of rotting in winter wet. If the roots appear dry, soak them in water for a couple of hours prior to planting. The brittle roots are fragile so handle carefully.

Dig a shallow planting hole 15cm to 20cm deep and wider than the roots. Position the centre of the crown on a mound of coarse grit, sharp sand or gritty soil, so the central growing point is around 5cm below the soil surface when covered. For best impact, plant in groups, spacing the crowns about 30cm apart.

Prune hybrid tea and floribunda roses now to generate vigorous, new season growth for flowering in summer. Start by pruning out any dead wood and remove all weak, damaged or crossing stems. For hybrid tea roses, prune the remaining stems down to about four buds (10cm to 15cm) from the base or from the point where last year’s growth began. On floribundas, prune to about six buds or around 25cm from the base. Keep in mind when making pruning cuts that new stems will develop in the direction in which the top remaining bud is pointing. Good air circulation is important to maintain rose health so, most cuts should be made to just above an outward-facing bud to produce airy, open-centred bushes.

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