Monthly Masterclass: June


Do it: weed control

Weeds, Winterbourne House and Garden, Digging for Dirt

Himalayan balsam (1), hairy bitter cress (2) and goosegrass (3), photograph by Andrew Gee

Step 1

No matter how much preparation work has taken place the odd weed species will always appear in summer ready to challenge ornamentals in a battle for supremacy. Annual weeds reproduce in a single year before the parent plant dies leaving only offspring behind. Some, like hairy bittercress, spread but pose little threat to larger border plants. Others, such as goosegrass, will scramble vigorously and inhibit their growth. Both can be easily removed by hand or garden hoe being careful not unearth too much soil which can disturb long-dormant weed seed and result in germination. Other annuals are less obliging; an average sized Himalayan balsam contains 800 seeds fired up to 11m by exploding seed pods. The plant must be pulled from the ground or cut below the lowest node before it has flowered and distributed seed. Those left rooted with several nodes remaining will simply re-grow and flower before the end of summer.


Weeds, Winterbourne House and Garden, Digging for Dirt

Bindweed (1), horsetail (2) and Japanese knotweed (3), photograph by Andrew Gee

Step 2

Perennial weeds pose an even greater challenge appearing year after year and often sprouting from the smallest piece of broken root. Some, such as bindweed or horsetail, are extremely deep rooted travelling several meters below ground. Here, digging out established plants is unfeasible. However, repeated pulling of the foliage above ground over several seasons can seriously weaken growth and even eliminate the weed altogether. Japanese knotweed is far more persistent and where total excavation is not possible a recommended systemic herbicide used in accordance with the manufacturer’s instructions will be most successful. This is best applied when the plant is about 1m tall but Japanese knotweed is so vigorous it will probably continue to grow. Re-growth should be treated again in late-summer and checked the following spring.


Weeds, Winterbourne House and Garden, Digging for Dirt

Foxglove (1), Olympian mullein (2) and ivy (3), photograph by Andrew Gee

Step 3

Annual weeds can be composted as long as they have not set seed which can sometimes survive the composting process and germinate again when later applied as mulch. Perennials on the other hand must never be composted and some, such as Japanese knotweed, are even classed as ‘controlled waste’. These weeds cannot be included in general or green waste collections but instead should be disposed of at licensed landfill sites or dried and burnt in the garden. Not all weeds need such drastic treatment and in fact many are removed unnecessarily to the detriment of the environment. Self seeders like the foxglove or Olympian mullein, can be colourful welcome additions impacting little upon other established plants, whilst other common garden invaders, like ivy, provide a source of early winter nectar for late flying bees, wasps and butterflies.


Grow it: catmint

 What: Nepeta, or catmint, is a summer flowering herbaceous perennial producing mainly purple flowers, occasionally yellow or white, which grows between 30 – 100 cm tall. 

Where: Grow in full sun or the lightest shade in a free draining soil with other cottage or drought resistant perennials and shrubs. N. govaniana is the common exception preferring cool and moist conditions.

How: Cut back to new growth at the base following the first flush of flowers and a second will follow continuing until early autumn. Repeat again once flowering has finished completely in preparation for winter.

Nepeta x faassenii in the Walled Garden, Winterbourne House and Garden, Digging for Dirt

Nepeta x faassenii and Alchemilla mollis in the Walled Garden

When: Plant in spring and water well until established. Water stressed plants will be susceptible to mildew in this early period. Take softwood cuttings in early summer or divide plants in spring and autumn.

 The Gardener’s Verdict:

Nepeta is an ever-present at Winterbourne in June when it springs forth with sprays of lavender coloured flowers which come in two glorious waves at either end of the summer. These repeat flowers in combination with its aromatic, grey-green leaves give Nepeta an advantage over many inferior rivals with uninspired foliage and a much shorter season.

Nepeta looks best in the front of a border or next to a path where it can sprawl but still be seen and the scented foliage will be disturbed by passersby. It greets visitors here lining the path leading to the front entrance, planted alone beneath climbers along the Pergola, and in combination with other perennials in the Walled Garden borders.

In recent years, N. ‘Six Hills Giant’ has become the most popular. It is bigger than most, growing to nearly 1m tall, and extremely reliable. However, it can also be so vigorous that it flops under its own weight and collapses totally in heavy rain. We grow the common N. x faassenii most often. It is a little less spectacular but tidier in habit and rarely requires staking.

Nepeta combines best with cool-colours and in particular pastel shades. Front-of-border staples such as Alchemilla mollis will intermingle happily and taller plants, such as roses, benefit from being planted behind where their bare lower branches are covered by the shorter perennial. Otherwise, the movement of breezy grasses, such as Miscanthus, compliments Nepeta well whilst more impervious forms, such as Phlomis, provide contrast and give some solidity to the scheme.

Of course, cats love Nepeta and will often flatten an entire plant in a fit of frenzied pleasure. A sacrificial pot of the much duller N. cataria, or catnip, should be enough to keep neighbourhood cats away from the showier hybrids favoured by gardeners. For those that can’t escape feline attentions, Perovskia ‘Blue Spire’ and Caryopteris ‘Dark Knight’ will both produce similarly coloured flowers and foliage without the furry friends.”

Daniel Cartwright, Outdoor Area Supervisor, Winterbourne House and Garden


Read it: Monthly Masterclass: May

The handkerchief tree has to be one of the most spectacular of all flowering trees. Catch up with last month’s Monthly Masterclass: May to find out how to grow a handkerchief tree all of your own or what to plant instead if you just don’t have the room.

Davidia involucrata, photograph by Jenny Lilly, Winterbourne House and Garden, Digging for Dirt

Davidia involucrata, photograph by Jenny Lilly

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