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Give new shrubs the best possible start

by Timber Press on January 15, 2019

in Design, Gardening

The hardy lilac, Syringa vulgaris, grows on most soils, including clay. However, good ground preparation prior to planting helps establishment and encourages a live display of flowers.

A shrub is a long-term garden plant. Its success in your garden depends on you. It is not only about where you plant it but also how you plant to ensure good root development and establishment, encouraging it to grow, develop, and thrive. You need to ensure that the growing conditions in your garden are as good as, or better than, those it enjoyed in the nursery.

Ground preparation
Preparation of the planting site is vital to encourage those roots to spread out from the growing medium or soil that the shrub started life in. Few gardens have deep, well-drained, fertile soil that needs little preparation. So fork over the area thoroughly to a depth greater than the roots of the shrubs you are planting and incorporate plenty of good garden compost, well-rotted manure, or any organic soil conditioner. This is especially important on poor, sandy, or chalky (shallow alkaline) soils, or on heavy clay. The organic matter helps to improve the soil structure. If existing shrubs, hedging, or conifers have been removed, be even more generous with the soil conditioner and add a concentrated organic fertilizer such as chicken manure pellets.

Poorly drained and very heavy clay soils can be improved by adding coarse grit or sharp sand. If the planting site is dry, water thoroughly and gently a day or two before planting.

Planting container-grown shrubs
Most shrubs are grown in pots for sale through garden centres and other gardening outlets. Always look for healthy stock that does not appear pot bound or as if it has been struggling in the same pot for a few years. Before you plant, water the shrub in its pot thoroughly; submerging the pot in a bucket of water until it stops bubbling is ideal. If you plant when the growing medium is dry, water often fails to penetrate the rootball once it is in the ground.

Dig a hole at least twice the size of the pot and thoroughly fork over the base of the hole. Sprinkle a handful of balanced, slow-release fertilizer around the hole and into the soil you will use to backfill around the plant.

Now carefully remove the shrub from its pot. If the roots look nice and healthy and are fairly loose around the edge of the rootball, leave them undisturbed and position the plant carefully in the planting hole.

If the rootball is densely packed, the roots appearing knotted together, you can gently tease out some of the roots from the base of the rootball and spread them out in the planting hole. Some recommend cross-cutting the base of the rootball with a knife to encourage branching. This is a matter of personal preference and is best only attempted on vigorous deciduous shrubs that are likely to grow easily.

Ericaceous subjects, such as rhododendrons, have dense, fibrous root systems and should be planted undisturbed. Roses have bony tap-root systems that never form a rootball. The growing medium is likely to fall away when they are planted, so adding mycorrhizal fungi to the planting hole is advisable to encourage establishment.

Settle the plant in the planting hole so that the surface of the growing medium is just slightly below ground level. Backfill with soil and fertilizer and firm around the rootball with your fist or foot. Ideally there should be a saucer-like depression around the shrub that will make watering easier. Now water thoroughly, even if the soil is moist or rain is expected. This is important to settle the soil particles around the roots.

Pot-grown rhododendrons have dense, fibrous root systems. They should be soaked thoroughly prior to planting, then planted undisturbed.

Planting root-balled shrubs
Some shrubs, especially conifers, are grown in the field, lifted during autumn and winter, and sold with the rootball and soil wrapped in hessian or burlap, sometimes with wire mesh around the outside. Lifting a root-balled plant is a skilled operation and great care is taken to keep the rootball intact with the soil to avoid breaking the roots. Take care when handling them and avoid dropping the rootballs when you move them. This easily breaks brittle young roots.

Ground preparation and planting are the same as for container-grown plants, but it is important not to attempt to remove the hessian or the wire cage. The hessian rots in the ground and the roots grow through the wire, so leave both alone. However, when the plant is positioned in the hole and you are ready to backfill, you can cut away some of the hessian from the base of the plant if it is likely to be left above ground after planting. This looks tidier and prevents its acting as a wick, drawing moisture from the roots.

Watering after planting and regular checking to make sure that plants are firm in the ground and have not been rocked by the wind are particularly important.

Planting bare-root shrubs
Some hardy, easy-to-grow shrubs are grown in the field and lifted when dormant during late autumn and winter. Deciduous hedging plants and roses are often sold in this way. The soil is not retained around the roots, but the roots are protected from frost and drying out, either by temporary planting, known as heeling in, or by wrapping them.

Here again good soil preparation is important. The roots must be moist when planted. If they appear dry, soak them in a bucket of water for a couple of hours immediately before planting. Ideally dig planting holes that are large enough for the roots to be spread out. If you are planting a large quantity of deciduous hedging plants, or whips as they are known, a mechanical soil auger to drill the planting holes is a massive benefit.

Using mycorrhizal fungi when planting aids establishment. This can be added as powder or granules, sprinkled onto and around the roots, or as a gel dip before placing the plant in the planting hole. The mycorrhizal fungi form a mycelium that grows in association with the shrub’s roots, aiding water and nutrient absorption and stimulating growth.

Plants should be really firm in the ground after planting, and thorough watering is essential.

Most hardy shrubs are easy to establish if planted with care in the first place. In temperate areas, where winters are not too severe, autumn planting is favourable because the soil is warm and moist and roots have time to establish before leaf growth is active. In colder areas it can be advisable to delay planting evergreens and borderline hardy subjects until spring.

When frost is expected beware of planting out shrubs that have been grown under the protection of a polytunnel or glass. Harden plants off by protecting at night or in severe weather until milder weather conditions prevail. However, it is a mistake to keep hardy deciduous subjects, such as Japanese maples, indoors before planting if they have previously been outside on a nursery. Keeping them indoors will stimulate soft, weak growth which is particularly vulnerable.


Andy McIndoe is the former managing director of Hillier Nurseries and Garden Centers in Hampshire, England. As designer of the Hillier exhibit at the Chelsea Flower Show for more than two decades, he has upheld the company’s unprecedented record of 68 consecutive gold medals. He is now a freelance speaker, writer, and consultant.



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