Kew's Broad Walk is in the process of a comprehensive redesign to create the longest double herbaceous borders in the UK. Stretching for over 300 metres from the Orangery to the Palm House Pond, these borders are being planted with swathes of vibrant summer-flowering perennials, grasses and bulbs to form a spectacular new horticultural feature.
Selected plants from Kew’s botanical collections will also be incorporated into the planting design. The first phase of this project was resurfacing the Broad Walk path with a resin-bound gravel surface and adding improved drainage. This part of the project was completed on schedule last autumn and since then mulching and planting has begun.
We are overjoyed to have passed the halfway point in the mammoth task of mulching the newly created borders! This event seemed insurmountable back in November when the Broad Walk team embarked on the daunting task of mulching the entire 320m length of the borders. With a healthy dose of extra help from students, staff and volunteers we have now made it to the stirrup.
Mulching is beneficial because it helps improve the soil structure and acts as a weed suppressant. Some areas of the border had become compacted and waterlogged, and adding mulch (along with the action of worms and weathering) can help break up and aerate the soil. The mulch is made in-house at Kew using soft green waste mixed with horse manure and straw. It takes a minimum of five weeks to break down and create a usable product. The dark mulch also looks attractive and helps protect plants from frost.
We will continue to work our way down the borders towards the Palm House. In addition to mulching, we are continuing to create neat bed edges using a motorised edging machine which cuts down to a depth of approximately 20cm. The remainder of the plants will go in at the end of March - these will be species that may not have survived the winter. These include lavender, Achillea (yarrow) and Stipa gigantea (golden oats), which need a warm period to settle in and establish.
Weeding is a perennial task on the borders - we must keep on top of this and prevent weeds from flowering and spreading their seeds. Once the plants have grown bigger they will begin to shade and crowd out the majority of weeds.
We are looking forward to the next phase of planting and to ensuring the borders look their very best for the summer.