Lawson cypress hedge care in Kent

Lawson cypress (Chamaecyparis lawsoniana) is a North American conifer that has been widely planted in UK gardens since the Victorian era. It is slower and more ornamental than leylandii, with a good range of cultivars offering blue-grey, gold and dark green foliage. In East Kent gardens, it turns up most often as a formal screening hedge along boundaries in Sandwich, Deal and the surrounding villages.

The maintenance principles are straightforward, but the one rule it shares with all conifers is absolute. Understand that rule and the rest is easy.

The one rule: stay in the green

Lawson cypress, like virtually all conifers, does not regenerate from completely bare brown wood. If you cut a stem back to the point where there is no green foliage left on it, that stem will not put out new growth. The result is a permanent brown patch or a dead section in the hedge.

This is different from a beech or privet hedge, which you can cut back to stumps and it will still regrow. With Lawson cypress, the green foliage at the outer surface of the hedge is effectively the "reserve" the plant draws on to recover from a trim. As long as you leave some green on every stem you cut, you will get new growth. The moment you remove all the green from a section, that section is done.

The practical implication: never try to reduce a Lawson cypress hedge dramatically in a single year. Take a little off each time. Keep every cut surface in the green zone.

How to trim a Lawson cypress hedge: step by step

Step 1: Choose your timing

The main trimming window is May to August. Cut during active growth and the hedge recovers quickly, covering the cut surfaces with new foliage before winter. A single cut in late May or June is enough for most established hedges. If the hedge grows vigorously (some Lawson cypress cultivars put on 60 cm a year), a second light trim in late August is worthwhile. Do not trim in late autumn or winter, as freshly cut foliage is vulnerable to frost damage and there is no active growth to heal it over.

Step 2: Check for nests and wasp activity

Walk slowly along the hedge, watching for birds entering and leaving and for wasp flight paths. If nesting is in progress between March and August, stop. The law is clear.

Step 3: Set the height and line

If the hedge has grown taller than you want it, decide how much to remove this year. As a safe guide, take no more than 15 to 20 cm off the top. If you need to reduce it by 40 cm, plan on two or three seasons, not one. Use a string line or canes to mark the target level if you are working across a long run.

Step 4: Trim the sides first

Work from the bottom up on each side. Keep the blade angle slightly tapered (narrower at the top than at the base) so that light reaches the lower foliage. A perfectly vertical-sided conifer hedge shades its own base and the lower foliage dies back faster as the hedge ages.

Step 5: Trim the top

Work carefully, checking regularly from a distance that you are keeping a consistent height. Use the string line as your guide. On a tall hedge, a long-reach pole trimmer makes this step far safer than a ladder.

Step 6: Clear the debris

Conifer clippings are not ideal for a standard compost heap as the foliage is slow to break down and the oils can inhibit other composting materials. A council green-waste bin is the easiest disposal route. If you have a chipper, finely chipped conifer clippings can go on a path or on a bed as a temporary mulch, but keep them away from the base of the hedge itself.

Common Lawson cypress cultivars in Kent gardens

Alumii: narrow, upright habit with blue-grey foliage. One of the most widely planted hedge forms. Grows 30 to 50 cm a year in reasonable conditions. Very common in Deal and Sandwich gardens planted in the 1970s and 1980s.

Columnaris: similar to Alumii but slightly more compact. Good for a formal, narrow screen where space is limited.

Green Hedger: bright green foliage, faster growing than Alumii, good formal hedge plant. Less common but occasionally seen in newer plantings.

Lane: gold-yellow foliage, upright habit. Often used as a specimen but sometimes planted as a mixed or informal screen alongside green forms.

How fast does Lawson cypress grow?

Once established (after two to three years), expect 30 to 60 cm of new growth per year depending on the cultivar, soil conditions and rainfall. In Kent's chalky soils, growth tends to be at the slower end unless the hedge is fed and watered during dry spells. On the sandy, free-draining soils around Sandwich Bay, young hedges may need supplementary watering in their first two or three summers to establish well. See our guide to hedge care in summer and drought.

Lawson cypress versus leylandii: which to plant?

Leylandii is faster and cheaper to establish a screen with, but grows so quickly that it requires cutting twice a year and can still get out of hand rapidly. Lawson cypress is slower, slightly more expensive to establish, but easier to hold at a given height long-term and more ornamentally interesting. For gardens in Woodnesborough, Ash or Eastry where a formal screen at 2 to 2.5 metres is the goal, a slower-growing Lawson cypress cultivar is often the better long-term choice. See our guide to leylandii and conifers for a comparison, and our choosing a hedge species guide for East Kent soil and exposure considerations.

Phytophthora: the main disease risk

Phytophthora lateralis is a soil-borne water mould that is lethal to Lawson cypress. Symptoms begin with yellowing foliage at the base of individual plants, progressing to total collapse. There is no cure. It spreads through infected soil, water movement and on contaminated tools and boots. In East Kent's relatively dry climate, the risk is lower than in western parts of the UK, but if your Lawson cypress hedge starts dying back in sections, particularly after a very wet winter, have it looked at by an arborist before assuming it is a trimming or maintenance issue.

Garden Ninja (Lee Burkhill, BBC Garden Rescue presenter and RHS-qualified garden designer) covers conifer care and pruning in detail on his YouTube channel, including the bare-wood rule explained visually. His channel at youtube.com/@Gardenninja has over 100,000 subscribers and is one of the most practical UK-focused gardening resources available.

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