The Border in Its Prime: How to Keep Your Planting Looking Magnificent All Summer

June is the moment your border earns its keep — but a little timely attention now means it keeps giving right through to September

Stand in front of a well-planted mixed border on a mid-June morning and it is difficult to imagine wanting to be anywhere else. The begonias are blazing in orange, yellow and red along the front edge, the salvias are throwing up their deep blue-purple spires through the middle, and the hydrangeas are opening into soft mopheads behind. Tucked between them, sweet william and phlox add their own vivid punctuation. It is full, generous and unapologetically colourful — exactly what a summer garden should be.

June is this kind of border's opening act, and it is a glorious one. The beauty of a mixed planting — annuals, tender perennials, bedding plants and shrubs all growing together — is that it offers more flexibility and more continuous colour than almost any other style of gardening. But it also rewards attention. What you do in these next few weeks will determine how the whole thing performs through July, August and into September. After many years of tending borders of all kinds, I've come to think of mid-June as the most important maintenance window of the entire gardening year.

Deadheading: The Task That Keeps on Giving

If there is one job that makes the biggest difference to a summer border, it is deadheading — the regular removal of spent flowers to encourage further blooming. Many perennials and all annuals will continue producing flowers as long as they are prevented from setting seed. The moment a plant achieves its reproductive goal, it begins to wind down.

Get into the habit of deadheading two or three times a week in June and July. It takes very little time once you are out there, and the difference in flowering longevity is remarkable.

Different plants require slightly different approaches:

• Roses — cut back to the nearest outward-facing bud or leaf with five leaflets, not just the dead flower head
• Geraniums (hardy) — cut the whole plant back hard after the first flush; new growth and a second flowering follows within a few weeks
• Delphiniums — remove the main spike once finished but leave the lateral shoots, which will produce smaller secondary flowers
• Dahlias — pinch out cleanly behind the spent bloom; the more you pick, the more they produce

EXPERT TIP
For repeat-flowering roses, don't just snap off the dead head. Cutting back to a proper bud lower down the stem produces a stronger new shoot and a better second flush of bloom. It feels more drastic than it looks, but the plant responds with vigour.

Staking: Better Late Than Never, But Earlier Is Always Best

If you haven't staked your taller perennials yet, do it now — this week if possible. Delphiniums, dahlias, tall salvias, phlox, and the larger geraniums all benefit from support, and the ideal time to put it in is when plants are about half their final height. At that point the foliage grows up through and around the stakes, concealing them entirely.

By mid-June you may have missed that window for some plants, but staking now is still infinitely better than nothing. A single heavy rainstorm or a gusty evening is all it takes to bring an unsupported delphinium to the ground.

Good staking options for different situations:

EXPERT TIP
Avoid tying stems too tightly to stakes — leave room for natural movement. A stem that can sway slightly in the wind develops stronger cell structure than one rigidly fixed in place. Snug but not strangling is the rule.

Filling the Gaps: What to Do When the Border Has Holes

Even the most carefully planned border has gaps in June. Perhaps a plant didn't come through the winter, or something has underperformed, or you're simply waiting for a later-season perennial to bulk up. Gaps are normal. What matters is what you do with them.

This is exactly the moment to use annuals. Hardy annuals sown in situ in April — cosmos, ammi, scabious, calendula — will be coming into their own right now and can be used as gap fillers that perform beautifully through summer. If you didn't sow earlier, well-grown annuals from a nursery or garden centre can be planted out now and will establish quickly in warm June soil.

A few annuals that earn their place in a perennial border:

• Cosmos 'Purity' or 'Sensation' — airy, tall, flowers until first frost
• Ammi majus — white umbellifers that look like wildflowers and attract beneficials
• Nicotiana sylvestris — dramatic architectural plant for partial shade gaps, wonderfully scented at dusk
• Verbena bonariensis — technically a tender perennial but behaves as an annual; flowers from July, self-seeds freely

EXPERT TIP
When using annuals as gap fillers among established perennials, water them in thoroughly and then leave them to it. Annuals establish faster with slightly less fuss than perennials and will knit into the border quickly once their roots reach down into warm soil.

Watering Wisely in Early Summer

June can fool you. The days are long and warm but the soil often retains moisture from spring, and established perennials have deep enough root systems to find what they need. Over-watering at this stage does more harm than good — it encourages shallow rooting and creates plants that become dependent on regular irrigation rather than developing resilience.

The plants that genuinely need attention are:

1. Anything planted this spring, which hasn't yet established a deep root run
2. Plants in containers, which dry out rapidly in warm weather
3. Wall-trained plants, where the soil at the base of a fence or wall is often extremely dry
4. Anything showing signs of stress — wilting in the morning (not just afternoon heat-wilt) is the key indicator

Water deeply and infrequently rather than lightly every day. A good long soak once or twice a week does far more good than a daily splash. Watering at the base of the plant, rather than over the foliage, reduces the risk of fungal disease and ensures water reaches where roots actually are.

EXPERT TIP
If you're unsure whether to water, push your finger into the soil to the second knuckle. If it feels damp, don't water. If it's dry at that depth, water thoroughly. This simple test saves enormous amounts of water and prevents the over-watering that is responsible for more plant failures than drought ever is.

The Chelsea Chop — Still Worth Doing

If you haven't heard of the Chelsea Chop, it is one of the most useful techniques in the summer border gardener's toolkit. The idea is simple: in late May or early June (around the time of the Chelsea Flower Show, hence the name), you cut certain late-summer perennials back by about a third to a half. This delays flowering by two to three weeks and results in shorter, bushier, sturdier plants that rarely need staking.

It works particularly well on:

• Sedum (Hylotelephium)
• Helenium
• Phlox
• Echinacea
• Rudbeckia
• Asters

You can also use the Chelsea Chop to stagger the flowering of a single plant — cut half of the clump back and leave the other half untouched. The two halves will flower in sequence, extending the display by several weeks.

EXPERT TIP
Don't be tempted to chop everything. Plants that are already in bud, or early-flowering perennials like geraniums and salvias, should be left alone. The chop is specifically for plants whose main flowering season is July through September.

Take a Moment to Look

Amid all the deadheading, staking and gap-filling, do not forget to simply stand still and look at your border. June is fleeting and the border at this moment — abundant but not yet tired, vivid but not yet overblown — is something worth properly noticing.

Take a photograph from the same spot each week through the summer. Note what is working and what is not, which combinations please you and which feel slightly wrong. Jot it down while it is in front of you, because by October the details will have blurred and winter is a surprisingly difficult time to remember exactly what June looked like.

The garden is always teaching you something. June is one of its finest lessons.