This is one of the questions I am asked most often, and it applies to almost every hedging plant I work with, not just one species. The top and middle of the hedge look full and healthy, but down near the ground there is nothing, just bare stems, gaps you can see straight through, and a strip along the base that never seems to thicken up no matter how the hedge is trimmed. It is frustrating, because a hedge that is bare at the bottom rarely does the job you planted it for. It stops giving you privacy exactly where you need it most.

The good news is that this is almost always fixable, and it is rarely a sign that anything is seriously wrong with the plant. It is usually the result of how the hedge has been shaped, how much light is reaching the lower growth, and how it has been fed over the years. All three of those things are within your control.

Why hedges go bare at the base

The most common cause I find is light. As a hedge grows, the top and outer surface naturally put on the most vigorous growth, because that is where the most light falls. Left unchecked, the top of the hedge widens out and effectively forms a canopy over the lower growth, shading it. Foliage that does not get enough light will not sustain itself indefinitely. It thins, drops, and eventually the lower part of the hedge is left with bare wood and very little green cover at all.

The second cause is shape, and it is closely tied to the first. A hedge that is wider at the top than at the base, even slightly, will always struggle to keep growth low down. This is one of the most common shaping mistakes I see in Irish gardens, and it usually happens gradually and unintentionally over several years of trimming the sides straight up and down, or trimming the top less carefully than the sides.

The third is feeding, or the lack of it. A hedge growing in soil that has never been properly fed or improved will struggle to put out strong new growth anywhere, and the lower part of the plant, already disadvantaged by shade, is usually the first place that shows it.

Good pruning from day one

If you are planting a new hedge, this is the stage where a bare base is easiest to prevent altogether. The principle I always work to is simple: the hedge should never be wider at the top than at the base. Ideally it should taper very slightly inward as it rises, sometimes called a batter, so that light can fall onto every part of the plant from the ground up, not just the top and outer face.

The second habit worth building in early is trimming the sides from the first year, rather than waiting until the hedge has reached its final height. Light, regular trimming in the early years encourages the plant to branch and thicken low down while it is still young and responsive. A hedge that is left to grow tall and untrimmed for its first few years, with all the early pruning attention going to height rather than width and shape, very often ends up with the bare base problem built in from the start.

If the hedge is already established

Correcting a mature hedge that has gone bare at the bottom takes patience, and I would always recommend thinking of it as a project over several seasons rather than a single fix. Trying to force an established hedge back into the right shape in one aggressive cut can do more harm than good, particularly with evergreen species, which do not always respond well to sudden, heavy renovation.

The general approach I use is restorative pruning spread over two to three years. Rather than cutting hard on all sides in one go, reduce and reshape gradually, correcting the taper a little more each year and allowing the plant time to recover and put on new growth between cuts. Deciduous hedges such as beech, hornbeam, privet and hawthorn tend to tolerate harder renovation cuts and will regenerate from old wood reasonably readily. Many evergreens, including photinia and laurel, will also regenerate from harder pruning, but I still prefer the gradual approach on these, particularly if the hedge is already under any stress. Species vary in how well they respond, and if you are working with a particular hedge type, it is worth reading the specific guidance for that plant before you start.

Let light back in

Correcting the shape is only part of the job. If the top of the hedge has become dense and congested, simply tapering the outline will not be enough on its own, because the inner growth may still be too thick for light to penetrate down to the base. Thinning out some of the congested growth within the canopy, not just trimming the outer surface, allows dappled light through to the lower stems and gives them a genuine chance to respond. This is a step that gets missed more often than any other, because it is less visually satisfying than a clean, tidy outer cut, but it often makes the difference between a hedge that recovers and one that does not.

Feed from the ground up

None of this pruning work will achieve much if the soil beneath the hedge cannot support the new growth you are trying to encourage. Good feeding, ideally starting before planting and continuing through the first several years of a hedge's life, gives the plant the resources it needs to respond to the light and shape corrections rather than simply sitting there.

I always work on the soil first. Working organic matter into the planting area before a hedge goes in, and then continuing to feed it well through establishment, sets a hedge up to fill out properly from the base rather than needing correction years later. For an established hedge that has gone bare, the same principle applies. A feed based on biochar improves the soil's ability to hold and release nutrients over time, rather than delivering a short burst that fades quickly, which is exactly what a recovering hedge needs. I go into this in more depth, including what and when to feed, in my guide to what to feed hedges in Ireland and when.

When it may be more than pruning and feeding

Occasionally a bare or thin hedge is showing something other than simple light starvation, particularly after a wet winter, when waterlogged soil puts real stress on root systems and can mimic or worsen the same symptoms. If your hedge is red robin specifically and you are seeing patchy weakness alongside general bareness, it is worth reading my dedicated guidance on red robin hedges, which covers soil, waterlogging and disease in more detail.

If you are not sure what you are dealing with, that is exactly the kind of question I would rather answer directly than have you guess. Ask Peter is there for that.