Why Autumn is the Best Time to Plant Hardy Perennials

Autumn is one of the best times of year to plant hardy perennials — and yet, for reasons that are hard to fathom, it has rather fallen out of fashion. If you have a project in mind — a new border, a redesign, a planting scheme to establish from scratch — this is the season we are increasingly recommending to our customers who garden on free-draining soils. The soil is still warm, autumn rainfall is on your side, and plants have weeks of good growing conditions ahead of them before winter arrives.

This is, above all, advice for larger planting projects. Pot-grown perennials can of course be planted at any time of year when the ground is open and workable, and topping up a border with a few plants on a summer’s day is perfectly fine with a little extra watering. But when it comes to something more ambitious, timing really does matter.

Why Did Autumn Planting Fall Out of Fashion?

Planting in autumn is not a new idea — far from it. Before container growing became widespread in the 1960s and 70s, most trees, shrubs, and herbaceous perennials were sold bare-rooted. They were lifted in autumn or spring, and planted accordingly. Autumn and spring were simply the natural planting seasons, dictated by how plants were grown and sold.

Container growing changed everything. Suddenly, pot-grown plants could be sold and planted at any time of year, and the old seasonal rhythm began to fade. Spring, with its sense of renewal and the irresistible pull of new shoots emerging after a long dark winter, became the dominant planting season in the popular imagination. It’s hard to argue with that instinct — there’s nothing quite like the enthusiasm that comes with the first warm days of the year.

Plant retailers — and we include ourselves here — have perhaps played a part in this shift too. We talk about planting bulbs in autumn, and then our attention quickly moves on to Christmas. Autumn planting for perennials, shrubs, and grasses rarely gets the attention it deserves. We’d like to change that.

A Changing Climate Is Changing the Calculation

Rosy Hardy, who has spent nearly 40 years running Hardy’s Cottage Garden Plants and holds 24 Chelsea gold medals, has been thinking hard about how gardening practice needs to adapt. “The books are going to have to be rewritten on what is resilient and what will work. Over the last four years, there’s been a dramatic change in the UK,” she says.

One of the received wisdoms she’s questioning most directly is the dominance of spring planting. “You need to stop planting by March because we’re creeping slowly into drought conditions then and by May it gets hot.” Instead, she advocates taking advantage of autumn rains by planting from September to November — a return, in many ways, to the rhythm that gardeners followed before container growing transformed what was possible.

And container growing has transformed it — in the 1960s and 70s, buying by mail-order meant that as soon as you received your plants you had to do something with them: pot them up or plant them out. Pot-grown plants arrive with an established root system, giving a higher success rate from the outset. You can see exactly what you’re buying, position pots around the border before committing, and plant when your schedule allows rather than when the season dictates. For busy gardeners, that flexibility is invaluable. But flexibility is not the same as indifference to timing — and for larger projects on free-draining soils, autumn remains the moment we’d choose above all others.

The Soil Still Holds Its Warmth

After months of summer sun, the soil retains a gentle heat well into October and even November. This warmth keeps soil biology active and creates the conditions in which newly planted perennials can settle in quickly.

Spring planting still has its place — particularly if you garden on a heavy clay soil that sits wet over winter, or if you live in a frost pocket. Experienced gardeners know to wait until the soil has warmed and dried sufficiently before putting plants in the ground. But autumn planting has a great deal to recommend it on the right soil, and a changing climate is making the case stronger still.

Time to Establish Before Winter

Autumn planting gives hardy perennials a crucial head start. Roots extend quietly through September, October, and into mild spells in November, anchoring the plant and building the reserves it needs to surge away strongly come spring. By the time April arrives, an autumn-planted perennial is already well into its second season of growth — visibly more settled.

There is a further, often overlooked advantage: pest pressure is significantly lower in autumn. The aphid populations, including Greenfly and Blackfly, that can overwhelm soft new spring growth are by this point in steep decline, giving newly planted perennials the chance to establish without the immediate pressures they might face in warmer months.

Use the Rain

One of the strongest arguments for autumn planting is one that is becoming more compelling with each passing year: the rain. The evidence that the UK’s climate is shifting is no longer a matter of future projections — it is already being recorded.

2025 was the warmest year in the UK series going back to 1884. The last decade (2016–2025) has been 1.33°C warmer than the 1961–1990 average. Winter half-years (October to March) are 13% wetter than the 1961–1990 baseline, and occurrences of very wet months have approximately doubled over the same period.

Source: State of the UK Climate 2025, International Journal of Climatology (Royal Meteorological Society)

Looking further ahead, the Met Office projects that this trend will intensify:

By 2070, UK summers could be up to 60% drier in some regions, with winters up to 30% wetter still.

Source: Met Office UK Climate Projections (UKCP), based on the RCP8.5 high emissions scenario

For gardeners on free-draining soils — sandy, gravelly, or chalky ground that never sits waterlogged — those wetter autumns and winters are an asset. Steady rainfall through the establishment period means roots can extend without stress, building the deep, resilient root system that will carry the plant through its first dry summer. Plant in spring instead, and a perennial on free-draining soil faces its most challenging conditions — heat and drought — before it has had time to find its feet.

The picture is more nuanced on heavier soils. Rosy has noticed that clay soils are proving surprisingly resilient in recent years: “Clay soils seem to be much more resilient, which is unusual considering they break open and crack, but the plant material in them seems to have a better root system.” That said, if your garden sits on heavy clay, lies in a frost pocket, or you’re considering borderline tender or drought-loving plants, autumn planting carries real risk. For those situations, patience until late spring remains the right call.

The Right Choice for Free-Draining Soils

For gardens on sandy, gravelly, or chalky soils — soils that drain freely and warm quickly — autumn is simply the best planting window of the year for large-scale projects. These soils never sit cold and wet, so there’s no risk of roots rotting over winter. Plants establish with ease, and by the following summer they’re behaving as if they’ve been in the ground for years.

The key, as Rosy puts it, is understanding your soil in close detail — its texture, drainage, and water-holding capacity — and making planting decisions accordingly. “Plants don’t read plant labels,” she reminds us. Knowing your soil is the starting point for everything.

Whatever your soil type, all soils benefit from the addition of organic matter. Applied as a mulch in autumn, it will slowly work its way into the soil, improving structure, moisture retention, and fertility — whether you garden on free-draining sand or heavy clay, giving newly planted perennials the best possible foundation.

What to Plant Now

Autumn is the ideal time to establish the backbone of a cottage garden: hardy perennials, ornamental grasses, and robust shrubs. At Hardy’s, we grow the vast majority of our plants from our own stock, which means they’re already acclimatised to outdoor conditions and ready to go straight into the ground.

Browse our current availability and plant with confidence — autumn is on your side.

Frequently Asked Questions

Can I plant perennials in autumn on any soil?
Autumn planting works best on free-draining soils — sandy, gravelly, or chalky ground that doesn’t sit wet over winter. On heavy clay or in frost pockets, the risk of waterlogging is real, and late spring planting is often the wiser choice.

When is the best time to plant in autumn?
September and October are the sweet spot. The soil is still warm from summer, rainfall is increasing, and plants have several weeks of good growing conditions ahead of them before winter arrives. November plantings can still work on well-drained soils during mild spells.

Do autumn-planted perennials need watering?
Far less than spring or summer plantings. Autumn rainfall does most of the work. In a dry September, water in new plants well and keep an eye on them for the first few weeks, but once the autumn rains arrive they should need little intervention.

What’s the difference between bare-root and pot-grown plants?
Bare-root plants are field-grown, lifted and sold without soil, traditionally in autumn or spring. Pot-grown plants, which is how we sell at Hardy’s, arrive with an established root system and can be planted at any time of year — though for larger projects, autumn remains our recommended season.