Close planting

Sunday, 17 February 2019

A thick planting of coleus, shrimp plant and Alstroemeria

I have been pondering lately on the merits of planting things close together in the garden. I have always loved the look of plants merging together like a tapestry and covering every spare centimetre of the ground. This gives the profuse, overflowing effect that I saw and loved during my self-guided Grand Tour of English gardens more than 30 years ago. The creator of Sissinghurst, Vita Sackville-West, wrote about her planting technique as 'Cram, cram, cram, every chink and cranny' (1955), and Margery Fish, in her garden in Somerset, East Lambrook Manor, also practised close planting, believing that 'most plants seem to do better when growing close to their neighbours than in isolation' (1964).

Rhizomatous begonia, polka dot plant and other groundcovers in a dense planting

Traditionally, the doctrine was that plants need to be spaced well apart so that they don't compete with one another. However, I have noted, in this horrible hot summer, that the parts of my garden that are the most densely planted are the ones that seem to be coping the best with the challenging conditions. It's possible that the heavy cover of vegetation shades the soil, keeping its temperature lower and helping conserve the moisture in it to some extent. It also means that it is harder for weeds to get a foothold and compete with plants for water and nutrients. Taller plants shelter the lower-growing ones from the harshest rays of the sun, as well as providing wind protection, making a microclimate that benefits the grouping. Shrubs can offer climbing plants support, another benefit of close planting.

Flowers of parsley

In gardening folklore, companion planting has long been talked about, with the idea that particular plants are said to benefit the growth of other plants, broadly or specifically, and suggests a range of helpful plants. Marigolds, for example, are said to drive away nematodes through the release of the chemical thiopene. Garlic planted nearby to roses is said to discourage black spot and aphids. Mint supposedly repels moths and beetles. Nasturtiums are said to lure aphids away from other plants. Some flowering plants - such as Queen Anne's lace, most daisy flowers, alyssum and even parsley blooms - seem to attract beneficial insects such as lacewings that control aphids, thus indirectly helping nearby plants. Whether there is any scientific proof to these claims, I don't know, but these notions do suggest possible advantages of growing plants close together.

Pilea cadierei growing with bromeliads

Modern thinking about plants is that instead of existing in isolation, they communicate with one another in complex ways, exchanging information, such as warning each other when they are in danger, such as insect attack or presence of pollutants in the soil. Plants even seem capable of recognising their own species and restricting their root growth so as not to disadvantage their kin! Plants are even capable of feeding one another via a vast underground system of roots and mycorrhizal fungi. This is a fascinating area of gardening that I hope to explore more in a future blog, and it does suggest that close planting can potentially be a beneficial garden practice.

Crassula multicava growing with Tradescantia zebrina, liriope and bromeliads

In my garden at the moment, robust groundcover plants such as rhizomatous Begonia, Tradescantia zebrina, Pilea cadierei, Crassula multicava, Geranium macrrorrhizum and a number of low-growing Plectranthus are forming thick carpets between and beneath shrubs, interspersed with Tradescantia pallida 'Purpurea' and self-seeding polka-dot plants (Hypoestes phyllostachya) in various leaf colours. Bromeliads are excellent for massed plantings to completely fill in a dry, shaded area under a tree. All these plants are all easy to grow in Sydney's climate and cope well with our increasingly hot summers.

The other advantage of close planting that I have noted is that the dreaded brush turkeys, which seem to have invaded many Sydney gardens in recent times, tend to avoid area which are densely covered, in favour of areas where there is bare soil or mulch between plants, which they thoroughly enjoy scratching about in. I do put metal obelisks over newly planted specimens, as the turkeys seem to sense when earth has been freshly dug, and dig out the plants before they have been established.