Plant Association: Trees, Herbaceous, Bulbs, Ground Cover Plants

If you mix trees, shrubs, herbaceous plants (perennials) and bulbs together you can cover up the ground in layers from the trees down, as with the natural structure of the woodland. This creates growing conditions for other plants and when you have plants of varying heights, you can have really attractive planting schemes. ‘Ground cover’ on its own tends to be all the same height and rather boring.

Plants naturally thrive at the different levels in the conditions created by the taller plants and this is the essence of the trouble-free garden. In a dense wood or on a tree-covered bank there may be only ivy on the ground as it is the only plant that thrives in the low light conditions. But in a more open wood there will be tall shrubs, brambles, herbaceous plants and bulbs. By choosing the right plants you can have them happily growing together, in the way that they have been selected for sections of each garden.

The main objective when choosing plants for a ‘little work’ garden is to have every inch of the soil surface covered by plants. That way there is no room for weeds. Plants and mixes of plants that need no more than an annual trim, prune or tidy up, mulch and feed are ideal. The plants that naturally keep the weeds down tend to be thick and bushy or to run underground with a dense network of roots and a mat display of foliage or spreading branches.

If the plants are not carefully chosen to mix well together, (see plant guide for each garden design), they will grow into each other and the more vigorous ones will eventually take over. As illustrated in several of the garden layouts, one way to keep one plant from overtaking another is by laying paving stones or runs of bricks between them. This gives a formal effect dominated by the paving or bricks.

So each plant needs to be distinct in foliage, habit or flower in its own right. A large number of plants have quite a different pattern in winter: there are shrubs that are evergreen or deciduous; and some herbaceous plants die right down to the ground in autumn while others keep a cover of leaves just above the ground. These evergreen herbaceous plants are very useful to keep the earth covered in the winter months when many gardens tend to look bare.

Epimediums have nice leathery leaves while comfrey (Symphytum) and some cranesbills (geraniums) have soft, furry leaves. Lamium (deadnettles) have a white stripe down the centre of the leaf and the leaves of the variety Beacon Silver are silvery white. These are good spreaders as ground cover. Some plants which form a clump, such as hellebores, need to have several planted close together so that they join up when the clumps get bigger. Their leaves are large and fingered so they make an interesting contrast to the other plants.

Trees for the Small Garden

One or two trees in a small garden give a feeling of height and space, but choose upright growing varieties. A spreading tree will dominate the garden and give much less chance to vary the planting beneath.

natural structure of woodlandIn a large garden a clump of three or more trees will provide a shaded spot where shade-tolerant shrubs and perennials such as bergenia, hostas, sarcococcas and Solomon’s seal can be planted.

Really dense shrubs such as choisya (Mexican orange blossom), Viburnum plicatum Mariesii, hydrangeas, spreading junipers (Juniperus pfitzerana types), Lonicera pileata (shrubby honeysuckle) and Cotoneaster salicifolius ‘Repens’ do not really allow anything to grow under them except perhaps snowdrops under hydrangeas and viburnum, both of which are deciduous. Early flowering bulbs like snowdrops die down before the shrub comes into leaf and create a solid mass of foliage which makes the ground below too dark for the weeds to get a chance!

Then there are the more open shrubs that need herbaceous plants under them to keep the weeds down, as their open habit lets more light through and weeds can easily get established. Some are upright shrubs and can be used in contrast. Buddleias, for example, have upright growth that arches over later in the summer. Lilacs develop a bare stem as they get older, as do most varieties of Japanese maple. Really upright shrubs like Viburnum Dawn and Pereskia can have low shrubs around them as well as herbaceous plants.

Herbaceous Plants

The following herbaceous plants all tolerate some shade and can be found in the plant lists. Like most plants from woodland habitats, they are early flowering. The really easy plant to use (for a leafy cover) is the cranesbill Geranium macorrhizum. It is about 8 in (20 cm) high and has pink, purplish or white flowers in May. You can select the flower colour by choosing the right varieties. The foam flower Tiarella cordifolia has a mat of leaves about 4 in (10 cm) high and masses of plumes of creamy white flowers that look light and frothy. Symphytum grandiflorum (comfrey), which flowers in spring and is good for compost, has a slightly taller spread of larger leaves and ivory bells in spikes that fall between the leaves. These plants really do look after themselves, once established. They do not even need the dead flower heads removing and the autumn leaves quickly rot down into the soil and leave a fair cover of fresh green leaves on them for the winter.

The herbaceous plants recommended in this section look after themselves and make attractive clumps with foliage down to the ground. Peonies, Dictamnus (burning bush), Euphorbia poly chroma and griffithii are good, solid plants that are long-lived, and the tall grass Miscanthus sinensis and its colourful leaved varieties are also easy. Michaelmas daisies tend to wander a bit so unless you want them everywhere they should not be planted without thought.

The next layer, if you wished to imitate the natural structure of the woodland in plant association, would be bulbs, those undemanding darlings who require little and give so much.

Bulbs

One of the moments that gives me the greatest pleasure in our garden is in late spring, after the garden has rested for the winter and is suddenly awoken with a dazzling display of spring bulbs. The narcissi and daffodils are heralded by the earlier awakening of the snowdrops in February, and, in the sheltered tubs, hyacinths, grape hyacinths and tulips. Bulbs are the ultimate in low maintenance and a wonderful beginning to the flowering months to come.

Bulbs are so good-natured and undemanding: providing they have a yearly feed after they have flowered in spring, and their leaves are left to die down for six weeks before they are cut, they are absolutely no trouble.

In smaller gardens, the smaller daffodil is appropriate and it may be a good idea to choose shorter, early flowering varieties for planting in grass. February Gold is a wonderful one that spreads fairly rapidly, although I have only once or twice seen it in flower by the last day in February! Its cousin February Silver has pale yellow outer petals and does not spread rapidly (which means it is more expensive to buy). Jack Snipe and W. P. Milner also fill the bill.

cyclamen hederifoliumThe taller varieties are probably best in beds and borders, set back a bit so that the spring growth of the plants in front covers up the dying foliage. Plant them where they get full sun before the other plants come into leaf, and not in the shade of a dense evergreen or they won’t flower more than once.

Large daffodils such as King Alfred (deep golden yellow), Magnet (creamy white) and Ice Follies (pure white with a large flat yellow crown) are all lovely planted in the grass in a large space. But in well-drained soil the shorter late-flowering Jonquilla, a 12 in (30 cm) narcissus and Minnow, a small 10 in (25 cm) daffodil with delicate pink and light yellow blooms, are delightful.

For the back of a border Crown Imperials (Fritillaria imperialis) grow to 3 ft (90 cm) and make a magnificent show each spring as their great clusters of yellow or orange flowers tower above the other plants. Crown Imperials are better planted individually about 12in (30cm) apart. (Their corms have a very strong and unusual, foxy smell.)

Snowdrops are very appealing in grass or under deciduous shrubs. They should be planted just after flowering while still in leaf. Dry bulbs are rarely successful, so if you cannot find a specialist nursery that sells them ‘in the green’, beg some from a friend’s garden. It is quite safe to split them up into individual bulbs when planting, and they will multiply each year. You can go on and on dividing the clumps until you have a ‘carpet’ of snowdrops to herald the spring.

The sight of crocuses never fills me with anything more than faint admiration, although I appreciate that when little else is in flower and they appear in their hundreds in the park they do look wonderful. So providing you choose the colours the birds don’t eat and plant them on a well-drained lawn or in the front of a border where their narrow leaves are not too obtrusive when they die down, they are worth the little effort needed to plant them. The early flowering winter crocuses are more elegant than the spring flowering hybrids.

One of the loveliest of bulbs is the lily of the valley (Convallaria). In France on the first of May they give bunches of ‘muguet’ (lily of the valley) or muguet plants in the same way here we give camellia plants or bunches of flowers on Mother’s Day. The sweet smell and delicate white flowers of the lily of the valley are a delightful asset to any garden when they flower in late April or early May. They benefit from a good covering of peat, mulch, leaf mould or organic matter in the autumn and their leaves take a long time to die down. But they are lovely in the garden and delightful if picked to have in the house. And, like snowdrops, they multiply and multiply all on their own.

For the undiscerning, the root system of the lily of the valley is not dissimilar to that of ground elder, and I made the mistake of asking a novice gardener to weed a bed in which there was ground elder and where the lily of the valley had died down. I regret to say he managed to pull up hundreds of yards of lily of the valley roots and leave the ground elder intact. ‘Cleared that for you,’ he said happily as he pushed the wheelbarrow full of the roots of one of my favourite spring bulbs towards me. So I had to weed the bed and replant the lily of the valley roots myself.

But bulbs don’t begin and end with daffodils, hyacinths, tulips, bluebells (Scillia) and other bulbs that flower in the spring. There are the wonderful lilies such as the hardy Lilium macklinae and the sweet-smelling Lilium regale, both of which flower in June and July.

Crinium powellii is a majestic bulb and bears beautiful autumn flowers if planted in a sheltered spot at the base of a wall where it is well protected.

The cyclamen, which flowers from October to March, is yet another splendid bulb, and the ever-useful bergenia flowers twice a year, is evergreen, trouble-free, shade-loving, wonderful ground cover beneath shrubs and attractive when planted to overlap on to paving stones or bricks. Bulbs that are ideal for planting under shrubs include the spring flowering aconite (Eranthis), Anemone blanda which has blue flowers and Chionodoxa gigantea, bright blue flowers. All die back until they reappear to glorify the ground without a grumble the following year.

Bulbs are a large and wonderful family and not to be overlooked.

Ground cover

To better understand the nature and function of ground cover plants, you have only to walk in the Alps of Austria or Switzerland. It was on such a walk in the Austrian Tyrol that I first saw many of our cultivated varieties growing wild.

alchemilla mollisIn their natural habitat not an inch of ground is left uncovered and there are stunning carpets of potentilla and late flowering azalea (stone rose), which are much smaller than when cultivated. These grow cheek by jowl beneath the trees with shade-loving hellebores whose delicate flowers appear before the snow has melted and Hypericum (St John’s wort), whose flowers and leaves are also much smaller and prettier than the many cultivated varieties, all proving that Nature herself is an inspired gardener.

Reliable and undemanding spring and summer ground cover plants such as Alchemilla mollis, campanulas and geraniums have their delicate leaves and blue flowers fluttering in the breeze, together with violets, anemones, Sedum and evergreen Ajuga reptans.

Nature doesn’t plan unimaginatively; she arranges luscious sweeps of colour and variety in the shape of the leaf. The balance between the vigorous, such as oxeye daisies and marjoram, and more delicate plants like pansies, violets, cornflowers, wild strawberries, forget-me-nots, cats paw, cowslips, auriculas and lilies of the valley, is controlled naturally. In the summer the cows are taken up into the high meadow to graze where they keep down the more vigorous plants and grass, allowing the smaller and more beautiful to continue growing.

But now that milk is so plentiful the danger is that only horses will be put out to pasture in the high alpine meadows and that many wild varieties will become extinct. The horses’ teeth will rip up the more delicate plants and leave only the tougher grasses, Erica (heather) and saxifrages.

One of the keys to keeping the work in the garden down to a minimum is having a good selection of hardy ground cover plants. Ground cover is usually fairly vigorous (sometimes too vigorous!) and will quickly cover the earth under trees and shrubs and save you a lot of weeding. Ground cover plants are either evergreen or perennials which die down in winter. But you need to choose the correct plant for the spot as some ground cover plants do better in the sun and others in the shade.

Hardy ground cover such as Geranium endressii ‘Wargrave Pink’ and Diascia rigescens and Diascia vigilis which are not quite so hardy, is particularly pretty; these plants have charming flowers, bright pink and dark pink respectively. They flower all through the summer then die down each winter.

The flowers of some of the other ground cover plants are insignificant but they have leaves that are colourful and interesting the year round, which certainly makes up for it. Whether it’s a dry sunny bank or dark shady corner, there’s usually a suitable ground cover plant

But should you have a bed of shrubs which are not likely to be moved, graded bark flakes or bark nuggets are ideal to cover the ground. They are very smart, give an elegant finish and certainly keep the weeds down if 3 in (7.5 cm) or so deep.

Ground Cover Plants

The following plants are trouble free, vigorous, spread easily, divide and most are evergreen -not a bad recommendation!

Sun-loving ground cover

Arabis (Rock Cress), grey/green foliage, small while flower. Excellent for sunny, well-drained soil. Lamium maculatum ‘Silver Beacon’, green/silver leaves, pink/purple flowers in May. Sedum ‘Ruby Glow’, pink flowers July/August, and Thymus ‘Silver Posie’ will do well in sunny, well-drained soil.

Campanula carpatica ‘Blue Chip’ is a vigorous grower with lovely blue flowers in July and August. Campanula garganica and Convolvulus mauritanicus are splendid for rockeries, dry stone walls and planted between the cracks on terraces and patios. Once it gets going campanula seeds itself.

Campanula portenschlagiana is a very ‘useful’ dwarf perennial with blue flowers from June to November. It is an invasive plant which will make its home happily between cracks in paving or brick walls. Prefers lightly shaded position. Once planted it will spread and seed itself everywhere.

Heuchera sanguinea ‘Bressingham Blaze’. Deep coral flowers in summer. Hardy herbaceous perennial.

Shade-loving or not fussy plants

Saxifraga umbrosa (London Pride) is not fussy. It is good in all soils and the shade. It has small rosettes of fleshy leaves and tiny pink flowers in May/June and spreads sloivly. Ajuga reptans ‘Atropurpurea’ is very good in shade. It likes a moist shady position. It has dark purple/green leaves and blue flowers in June and July.

Alchemilla mollis (Ladies Mantle). Delightful mid-green leafed herbaceous perennial.

Bergenia (Elephants’ ears). Pink flowers in spring. Large, round, flat, evergreen leaf Hellebores. Hardy winter flowering plant. Single open-faced flowers from white to plum purple.

Hostas. Summer-flowering herbaceous perennial with broad plain green and variegated leaved plants.

Pachysandra terminalis ‘Variegata’. Pale evergreen leaf edged with cream. Nice bushy shrub, grows to 6in (15cm), spread 18in (45cm) or more.

Primula vulgaris (Primrose) and Primula veris (Cowslip) will grow in any soil. Flowers in spring and a few flowers in autumn.

Skimmia japonica ‘Rubella’. Dark evergreen leaves, crimson buds all winter, turning to white flowers in the spring. (Can be used to pollinate a female variety and get lots of shiny red berries.)

Tolmiea menziesii ‘Taffs Gold’. Flat maple-like lime green evergreen leaves. Red flowers on spikes in June. Wonderful undemanding ground cover plant.

17. June 2013 by admin
Categories: Boundaries / Hedging, Flower Beds & Borders, Garden Management, Gardening Ideas, New Gardens, Types of Gardens | Tags: , , , , | Comments Off on Plant Association: Trees, Herbaceous, Bulbs, Ground Cover Plants

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