Head Gardeners monthly blog: September

9 September 2022

Well, what a summer we have experienced this year!  The temperatures have been scorching and our gardens have had to cope with extreme drought.

Here in Hampshire, we have had a hose-pipe ban.  You may have seen me on the local BBC news, giving advice on gardening in these extreme temperatures, and in last month’s article, I touched on some water-saving techniques for your garden.  I’d like to give you some further tips for planning a drought-resistant garden.  There are some useful techniques that maximise the effectiveness of the precious water we have available to use.

The first important consideration is water use.  Be sure to water immediately around plant and soak well once or twice a week.  You want the water to go down deep into soil, which will encourage the roots to grow down looking for it and give you a stronger plant.  If possible, use a seep hose or drip irrigation as opposed to sprinklers and water early in the morning or late in the evening to reduce evaporation.  Water wisely, by prioritising seedlings and those plants which are flowering or fruiting.  Harvest water from gutters to fill your water butts.  You can also use grey water from sinks, showers and baths during a drought.  It is perfectly acceptable to reuse water which contains mild detergent as soil and potting composts are effective at filtering them out.  Residues can sometimes even act as a mild fertiliser.  To minimise bacterial growth, use this grey water within 24 hours.

To reduce run off, plant either in a terrace or a saucer shape with a lip.  This will retain water and allow it to soak in.  Think of the soil as a sponge which needs to hold as much water as possible.  You can achieve this by adding organic matter, such as compost and well rotted manure, and making sure that you avoid compaction.  I would not recommend using peat as it is not environmentally sustainable.  You should also avoid working the soil in dry weather as this will accelerate moisture loss.  Mulch your beds with organic matter (up to 10cm deep) in the spring, while soil is moist.  This has the dual purpose of holding in water and preventing weeds.  If you do have any weeds, be sure to remove them so that they are not competing for water and nutrients.

Let’s turn our attention to planting.  Aim to transplant and plant trees or shrubs in the autumn as this will give them chance to establish a good root system before the next warm season.  Think about providing shelter from drying winds by planting in groups.  We know that woodlands dramatically reduce the air temperature, so consider an area of trees if you have room.  Planting ground cover plants such as Lamium maculatum, Vinca major, or Bugle will reduce soil exposure and help minimise evaporation.

I recommend growing plants with silver or grey foliage, as most are drought tolerant and can withstand full sun.  Senecio candidans – Angel Wings, can withstand very low rainfall.  It needs good drainage and a sunny position.  Stachys byzantia – Lambs ear, has attractive soft, woolly foliage and is reasonably drought tolerant once established.  Lavender and Rosemary both thrive in warmer temperatures and free draining soil.  Any plants with blue coloured leaves and a waxy surface are a good choice as these restrict water loss.

Eryngium (sea holly) has spiny leaves and a characteristic ruff around the flowerheads.  The thistle-like flowers are made of many tiny flowers packed together in a tight cluster.  The colours range from grey to intense blue and are good for attracting pollinating insects.  They need free-draining soil and can tolerate poor soil.  Nepeta (catmint) is a dependable perennial which produces a profusion of lavender-blue flowers.  These are tough plants which are easy to grow, low maintenance and can withstand full sun in dry soil with very little rainfall.  Another good idea is to choose succulents, as they store water in their leaves and are excellent at surviving heat with very little rainfall.

We are seeing signs of trees and shrubs going into autumn early as a response to drought stress, with leaves already showing colour or falling.  Shrubs such as the rhododendrons, azaleas and camellias don’t produce deep, searching roots and are prone to drying out, so we have been busy mulching to help them survive the drought.  Aim to mulch with a lime-free, ericaceous compost or bark to conserve soil moisture, insulate the shallow roots from heat and keep down competing weeds.  At the moment, these plants are setting their flower buds for next year’s floral display.  So, I do have some concerns over the effect that this year’s drought will have had.  Hopefully our efforts with mulching and watering will have been enough to reduce the impact on flower bud production.

Our Acer palmatum – Japanese maple, is already turning and beginning its autumn display.  The shortening days and cooler nights trigger these trees to prepare for winter.  Photosynthesis shuts down and green chlorophyll fades from the leaves, allowing other colours to emerge.  There are several pigments present in leaves.  The red in maple leaves comes from anthocyanin, which protects tree leaves from disease and drought, repairs leaf damage and acts as a natural sunscreen.  As the chlorophyll fades, the beautiful red hues emerge.

Flowering at Furzey Gardens in September is the Leycesteria formosa – Himalayan honeysuckle or pheasant berry.  This is a vigorous, deciduous shrub with erect sea-green stems bearing long, pointed ovate leaves and pendulous racemes of white flowers with showy red-purple bracts, followed by deep purple berries.  As well as looking attractive, this shrub is known for attracting bees and birds.  This is a robust and easily grown shrub which is widely available in garden centres and online.

September is the perfect month to plan and plant next spring’s bulbs.  Choose a catalogue from a reputable supplier and relax in the garden to ponder daffodils, snowdrops and tulips.  Try making a rough sketch of your flower borders to make a plan.  Planting bulbs together is a good idea to create colourful drifts of spring flowers.  If you’re planning to rearrange your garden over winter, it is helpful to take lots of photographs now to use as a reference point.

I love planning and anticipating the spring bulbs as they offer wonderful colour at a time of year when many other plants only offer muted colours.  Ideally, plant your bulbs by the end of this month at a depth at least two to three times their height and place them with their shoot facing upwards.  When you replace the soil on top of the newly planted bulb, firm it down gently with the back of a rake.  Avoid firming in with your boot, as you may damage the bulb.  I hope that I have given you some useful suggestions to start planning your garden for next year.

As we move into the next season, be sure to enjoy the last of the late summer perennials and the arrival of the autumn colour. I hope to see many of you at the gardens this month to enjoy a tranquil visit with late summer displays in our borders. The tea rooms continue to open seven days a week from 10am-4pm with a selection of light lunches and tasty cakes and pastries.

This article originally appeared as the monthly In The Garden column in the Lymington Times, buy the paper on the second Friday of every month to read the next column first.