Colourful cornus

Dogwoods (Cornus) are a shrub cultivated for their vibrant winter stems. They are renowned for their fabulous colour during the deepest, darkest winter months and are a great way to help lift and add a sparkle to your garden.

Harlow Carr’s Winter Walk features some beautiful dogwoods which have really shone and glowed this year. Pruning last year helped to enhance their colour and we are now ready for the annual prune again.

Pruning keeps the plant healthy and encourages new growth; it is this new growth which produces and provides the best stem colour. Here at Harlow Carr we carry out annual pruning on the Winter Walk to create that ‘wow’ factor. Ideally it is best to do this before the sap starts to rise and any signs of leaf growth. Pruning in late winter or early spring helps to minimise the risk of bleeding and entry for any pest and disease. By hard pruning - otherwise known as stooling - cutting right down to the lowest bud possible encourages the most growth. You will not see any buds at this stage but look down the stem for lines or markings to indicate buds, and cut above this. Try to cut as close to a potential bud as you can, otherwise you will be left with a stalk or stump and this can lead to dieback.

The size, location and condition of your Cornus plant may dictate how you wish to prune it. If it has never been pruned and is a large plant, it is best to remove a third of the oldest, thickest stems to the lowest bud possible to encourage new growth from the base; do this over a three to five year timescale. If your plant is mature and in a prime location in your garden and would leave a gaping hole, simply remove a third of the oldest wood, meaning you can still maintain height and structure within your border. Cornus ‘Midwinter Fire’ has lovely red and yellow fiery stems which ‘glow’ and is one I would recommend you stool and cut back hard each year to optimise the best colour possible. Books may advise you to treat this one a little more gently than some of the other species but our experience at Harlow Carr suggests otherwise: if you don’t prune hard the colour is noticeably duller and your plant will contain more dead stems, with colour only at the tips.

Cornus ‘flaviramea’ has lime green zingy stems; C. ‘Kesselringii’ is the darkest one of them all, having dark purple almost black stems. C. ‘Sibirica’ produces the brightest red stems. They can all be treated in the same way and hard pruned if desired over a three to five year pruning regime, depending on how you wish to treat your plant. It is important with any pruning you carry out to give the plant a feed with an equal balanced fertiliser of NPK (Nitrogen, Phosphorus, Potassium) or blood fish and bone is equally as good. Cultivate this well into the soil then apply a mulch as this will help retain moisture over the summer and help to minimise weed control.

If you have bought new dogwood plants, now is the best time to plant them as the soil is warming up and is moist and ideal for good root establishment. Don’t prune newly planted Cornus plants until they are at least a year old, giving time for a good root system to be developed. Once your plant is a year to eighteen months old you can begin your pruning regime.

The great thing is you can be as creative as you wish with your pruning. Cornus give brilliant colour and decoration, both inside or out. You can use the stems to make plant supports for herbaceous plants or supports for sweet peas, beans or peas. Perhaps best of all, you can have a go at propagating new plants from hard wood cuttings. They will take a while to root so be patient, but you’ll have a new plant for free!

With thanks to Tom White, Horticulturalist at RHS Garden Harlow Carr

JOBS TO DO

• Plant your potatoes

• Apply a lawn weed and feed

• Prune any Cornus you wish to before the sap rises

• Plant shrubs, trees and perennials as the soil is warming up and moist.

For more information on things to do in the garden this month visit rhs.org.uk

DIARY DATES

Spring Plant Fair

Sun 3 May, 10am - 4pm

Held in conjunction with Plant Heritage, specialist nurseries will be at the garden selling a range of quality plants. The RHS Advisory team will also be available to answer all your questions. Normal garden admission

The Harlow Carr Rhododendron Show

Sat 9 - Sun 10 May, 10am - 4pm

The Harlow Carr Rhododendron, Camellia and Magnolia group will be at Harlow Carr all weekend offering advice, guided woodland walks and an exclusive talk. View collections from local growers who will be showcasing the very best specimens the region has to offer in our Rhododendron competition judged by RHS judges. The competition is open to everybody so if you are interested in showing your own collection please visit the RHS website for more information. Normal garden admission