Gardening on a slope

GARDENING ON A SLOPE

Dundee town has grown around the Law Hill, Balgay Hill and even Menzieshill, so there is a fair bit of steep slopes incorporated into housing development land.

The challenge of a sloping garden will vary according to the degree of severity, the type of soil and whether the slope runs towards the house or away from it. Slopes can create a dry garden by allowing surface water to run off it, or a flooding problem if you are at the bottom of a hill. Problems of steep sloping gardens are usually left by the builders for the house owner to solve. However if the slope is severe and runs towards the house the builder is most likely to have tackled any potential drainage problem which could affect the property.  However it is always a wise move to check the property to see if there is any history of flooding or water damage.

For every negative aspect of a slope there is always the positive side. You may be blessed with a burn that can create a fantastic water feature garden. A rock garden  is perfect on a well drained slope. Many plants look better if viewed from below e.g. Fuchsias, Lilies, Himalayan blue Poppies, and some better if viewed from above e.g. Tulips.

The slope allows terrific scope for gardening creativity in both soft and hard landscaping so take time to consider all aspects before getting the spade out.

Drainage

If your garden is at the bottom of a slope, surface water causing local flooding after heavy rainfall could be a problem. Wet soil may be indicated if you see a lot of moss, sedges or buttercups. It may be sufficient to cultivate deeply to allow water to percolate through the soil, but if the flooding risk is high consider some garden drainage. This could be a simple drainage system of perforated pipes under a gravel path leading to a decent sized soakaway. A more ambitious project may be necessary with professional advice needed on depth, type and size of perforated pipe, backfill material, extent of run and connection to an outlet. If using a surface water outlet the connections are critical and must be done properly incorporating a catchpit so that garden silt or debris can be filtered out in a sump to be cleaned out periodically.

Access

After drainage, good access must be incorporated into the design to allow for weeding, planting, pruning and wandering around enjoying the garden. There must be plenty of flattish areas to work from connected by a path network. Strategically placed large bushes and trees can help to hold onto to assist stability. Footpaths on very steep slopes are best with a handrail for safety.

A path system may be formal with slabs, bricks, and breezeblocks, or it can be sympathetic to the landscape with natural wood risers backfilled with course wood chips. A trip to a builders merchants yard who specialises in hard landscaping can give many ideas to work on.

Retaining Walls and Terracing

Really steep banks may require retaining walls next to footpaths, but terracing with large rocks will give a more natural appearance. Good quality natural stone can often be acquired from builders yards if they have been doing any demolition of old buildings, or it may be purchased from a local quarry. The size of the job will determine whether it is done in house or whether a bricky or stone mason is employed. There are plenty of excellent dry stone wall builders who can create an attractive wall with strength. If cost is a factor breezeblocks can be used for speed and strength. Their formal appearance can be softened with ground cover plants allowed to trail over the edge.

Make sure any walls are strong enough to retain the bank for at least 50 years and provide weep holes for drainage.

Terracing is very useful to break the bank into a series of flat areas held up by as big rocks as you can find. During garden maintenance you will want to scramble over these rocks without fear of them toppling over, so size is important. A JCB may be needed to move big rocks around. Try to create a series of natural looking rock faces with the rocks relating to each other. Bury at least two thirds below ground. Create a series of plateaux  by cut and fill over the slope.

Decking

This can be an important option to create a flat patio adjacent to the house on a steep bank. Often there will be space left below the decking as the slope falls away. This is useful for storing garden tools or given over to the kids as a den to play in. Much safer than a tree house.

 Make sure your patio enjoys plenty of sunshine, some privacy and shelter from winds. Decking has been in fashion for a few years now, so there is plenty of information on materials, construction methods and maintenance of the wood. Make sure it is strong, the wood is well preserved and the design safe.

Plants for soil stabilisation

Once the slope has been hard landscaped, the planting can now be thought out. Terraced slopes and walls allow a fair bit of easy planting at waist height, so these areas can be more intensively gardened. Other areas of steep slope may be better with permanent planting, choosing plants that can hold the soil together to prevent any erosion.

I garden on several very steep banks with a fair degree of walls and terracing. Over time some plants prove much better than others in binding the soil surface together.

My favourites include Flag Iris, Delosperma, heathers, London Pride, Euonymous, variegated ivy, numerous dwarf spreading conifers, Shasta daisies, fuchsias, rhododendrons, azaleas and hostas.

For the larger garden use philadelphus, saskatoons, ceanothus, viburnums, kerria and cornus.

It always helps if bulbs can be interplanted as they can be very good at naturalizing. Bluebells and grape hyacinths are some of the best.

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Perfect Gardening Weather

 PERFECT WEATHER FOR THE GARDEN

Spring has been perfect this year. We had enough dry weather to catch up on outstanding tasks, complete the digging, and start the planting and sowing. Then the sun came out for a whole week and just as we were beginning to worry about the soil drying up, along came some serious rainfall.

The spring flowers were glorious and tulips have never lasted so long. The strawberries are two to three weeks ahead of last year and I have harvested my first lettuce and radish, and the sun lounger has been tested on several occasions. Well, I have to do my garden planning somewhere.

Every time I need to crack on with a bit of planting the weather turns dry, then once I’ve finished we get a bit of rain over night to water things in. This is just too perfect.

Is nature trying to make up for giving us two hard winters on the trot plus three wet summers. We lost a few plants in the winter, including some cistus, escallonias and cordyline, but those that survived are really putting on a brilliant display. My Fuchsia Mrs Popple was again frosted back to ground level, but it has survived and now has many young shoots reaching for the sun.

Flowers

The spring flowers will now be replaced with summer flowering bedding plants. Tubs, hanging baskets and beds have now all been replanted with geraniums, tuberous begonias, petunias, nemesia, busy lizzies and lobelia.

I grow some cosmos which is used to fill in any bare patches around the garden, and also sow some Shirley poppies which never fail to put on a good show.

Euphorbia polychroma has lovely lemon yellow flowers, but this year they are quite dazzling.

Azaleas are at their peak and really enjoying the moisture combined with cool but sunny weather.

Lilac is also superb with the white Mme Lemoine still favourite, and the deep lilac Michel Buchner also outstanding.

Himalayan blue poppies continue to flower, but remove the seedheads unless you wish to increase the stock. They grow fairly easy from seed if harvested when ripe and stored in a fridge for a few months. Sow them in a tray in late autumn and keep them outdoors all winter in a sheltered but shady place. Do not let them dry out and they should germinate in April the following year.

Iceland poppies also need regular dead heading to keep them flowering all summer. I also save the seed but sow them in late summer so I can overwinter small plants in trays for planting in early spring. These will then flower for the next two years.

Aconites grow quite easily from seed, so collect it as they ripen and sow it immediately where ever you wish to grow them. They naturalise rapidly.

Fruit

Apple and pear grafts are now shooting so I will soon have new varieties on two trees. I am looking forward to seeing pear Beurre Hardy and Christie and apples, Park Farm Pippin, Lord Roseberry and Pearl.

Mildew on apples overwinters in buds which open up in spring completely infected. These primary infections are quite noticeable, (they are completely white with mildew) so they should be picked off and destroyed before they spread.

Peach fruit set has been really poor. I think the severe winter did not help them. The blossom was quite late to open, (normally a distinct advantage), but never looked very strong, and although they got their regular hand pollination, assisted by a few bees most did not fertilise. They did not get any late frost. I hope to get three fruits this year and they will still be better than supermarket peaches.

Fig bushes got a fair frosting, killing back many shoots, but there is still a wee crop.

Allotment

All my fruit bushes are looking very good, but the gooseberry sawfly caterpillars have massed an attack. I spent an unpleasant moment picking them off and disposing off them. You need to be vigilant as they don’t hang about. They can chomp through the bushes at an alarming speed.

Strawberries are looking great and I may be picking my first fruit by the time you are reading this.

Planting has gone ahead at full steam. Sweet corn, cabbage, cauliflower, Brussels sprouts are all planted and seeds of Dwarf French beans, Swiss chard, lettuce, radish, spring onion, beetroot, turnip, and Swedes are all sown.

Leeks have germinated but are quite slow to grow.

Glasshouse

Tomatoes have established in the growbags and are now in flower, so feeding has started. The flowers get a daily tickle to spread the pollen which will assist fertilisation as the flower is cleistogamic. Just love that word !!! Google knows what it means.

If you are growing them as cordons, remove the sideshoots regularly and twist the growing stems around the supporting strings to keep them upright.

Grape vines are now showing the flower bunches. I cut back any non flowering shoots to a couple of leaves just to help feed the plant. The flowering shoots get cut back to two leaves after the flower bunch. Thereafter right through the growing season you must cut back all sideshoots regularly to one leaf. Black Hamburg is very reliable and is full of flower, but Flame, my red seedless variety and Perlette the new white seedless grape do not have as much flowers as I would like.

However my newly planted outdoor grape vine, Solaris has a couple of bunches on it. Gardening by the book, I should really remove them to let the new vine concentrate its energies into growing into a strong bush. I was never very great at doing the right thing and I am very curious to know if I can get a good outdoor grape to ripen in Dundee, so I may leave them alone for a bit, but keep the situation monitored. My outdoor Brant is very successful, but it has small bunches that are not very commercial, no matter how sweet and juicy they are.

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Rhododendrons and Azaleas

RHODODENDRONS AND AZALEAS

The first rhododendron I came across was R. praecox growing in a large drift in a bed of pure leafmould. This was at Dawson Park in 1960 when the park was in its early years and was not much more than a playing field with a few interesting plants to relieve the boredom. I won’t ever forget my first two years apprenticeship training, digging drains all winter at Dawson.  The highlight of the year was when that rhododendron flowered and that only lasted a couple of weeks, but it must have made an impact on me as I have never been without my R. praecox. It is one of the first to flower usually in March or early April but only if there are no frosts to shrivel up the delicate mauve flowers.

The following year I was working at Camperdown Park where mature rhododendrons grew all over the place. Training trips in spring arranged for the apprentices by our tutor Walter Gilmore took us to Edinburgh Botanical Gardens and Crarae Gardens where both Rhodos and Azaleas are grown on a massive scale but to perfection. I was hooked for life. Parks training helped me understand the range from the tall varieties to the dwarf evergreens and the deciduous azaleas, and that first bed at Dawson growing in pure leafmould made me realise the importance of giving them the correct type of acidic soil.

Today we do not have to go too far to see them in all their glory growing in natural surroundings covering the whole spring season. The gardens at Glendoick are now world famous as the place to visit to see hundreds of different rhodos, azaleas, camellias and numerous other woodland plants growing in a natural setting of a Scottish glen complete with a burn and waterfalls.

History

No article on rhododendrons and azaleas would be complete without some reference to the massive contribution made by several generations of the Cox family.

In the early nineteenth century the Cox family started a textile business in Lochee. This was consolidated by four Cox brothers in 1841 and the factory at Camperdown Works was reputed to be the biggest jute factory in the world employing 5000 people. Alfred Cox bought Glendoick House and estate in 1899. His son Euan, educated at Rugby and Cambridge, got a taste for the good life while working in London and had little enthusiasm to return to the jute business in Dundee.

A chance meeting in London with the plant explorer Reginald Farrer led Euan to join him in his first plant collecting expedition to Burma in 1919. The trip was a great success and many new rhododendrons and other plants were introduced. Euan loved to write about the new plants being introduced from all over the world and founded a bookshop in London. However this got bombed during the war and Euan returned to Scotland to help run the family jute business. He started to develop the gardens around Glendoick with his new seedlings from his expedition. He also subscribed to other expeditions and received many new plant introductions. A nursery was started with new plants acquired from other collections. Then his son Peter started to go on plant collecting expeditions to Turkey, India then China in 1981. The garden at Glendoick expanded up the burn.

The rhododendron nursery was established in 1953 and the garden centre in 1973.

Peter’s son Kenneth has maintained the family traditions with 9 plant collecting expeditions and written many horticultural books. Peter and Kenneth have been breeding rhododendrons for over 50 years to produce plants suited to small gardens and the Scottish climate.

For the full and fascinating story of Glendoick, the Cox family, and their involvement with rhododendrons and plant exploration, check out the website at www.glendoick.com.

Types and varieties

Most Rhododendrons are evergreen but the Azaleas may be evergreen or deciduous. They come in all sizes from a few inches tall to small tree sizes given time. Many of the deciduous azaleas, eg A. luteum are scented. The flowering season normally runs from April to June, but changes due to weather pattern at the time, and there is always a few types that will flower early or later throughout the summer. R. praecox can flower in late March but the flowers are not frost hardy so can get wiped out in a bad year.

If you have a large garden you can indulge some of the taller growing varieties such as Cynthia, a vivid scarlet, Pink Pearl, or Horizon Monarch a yellow with red buds.

For smaller gardens try Nancy Evans, a deep yellow, or Elizabeth, a brilliant red that has been a favourite for years.

Azaleas tend to flower a bit later, but many have an exotic woodland scent and orange flowers such as Gibraltar. Klondyke is a brilliant yellow and there are numerous others in reds, pinks, mauves and white.

Dwarf evergreen azaleas (Japanese azaleas) may only grow a couple of feet or so after ten years, but they are perfect for mass planting for ground cover. They are also very easy to propagate from cuttings. Glendoick have bred numerous new varieties in colours including pink, purple, scarlet, white, orange and crimson.

Site soil and planting

Most Rhododendrons and azaleas flower better in full sun in Scotland as we don’t suffer too many very hot summers. They associate well as woodland fringe plants with a backdrop of birch, rowan, pine, spruce or if you wish a flowering tree choose a cherry or Eucryphia Rostrevor. However make sure they are not shaded by the canopy.

An acid soil is a must with all of these plants. Fortunately most soils in this area are naturally acidic, but may have been limed for previous crops. They like a free draining soil that can hold moisture. Soils can be improved by digging in plenty of leafmould, composted bark, garden compost, pine needles or peat. Acidity can be improved by using sulphur chips and a pre planting light dressing of sulphate of ammonia and sulphate of iron, but not after planting as they may scorch young leaves.

Plant rootballed plants in the dormant season, but containerised bushes can be planted at any time provided they are always kept moist. Do not plant deep and any mulch should only be quite shallow as the fine surface roots do not like getting buried.

Rhododendrons and azaleas do not need much feeding, so a light annual mulch will be quite enough.

Pests and diseases

Mildew may be a problem on a few varieties, (Elizabeth is prone) but can be controlled with a fungicide used for rose mildew.

Azalea leaf gall, exobasidium, can be a problem on the Japanese evergreen dwarf azaleas. Pick off and destroy any galls as soon as you see them.

Vine weevil adults cut notches around leaves and can girdle the stem just above ground level. They produce white grubs that eat the roots.

Lime induced chlorosis is only a problem where the soil is not acidic enough.

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Herbaceous and border plants

 HERBACEOUS AND BORDER PLANTS

The garden border has evolved over many years as the place around the house to grow herbs for culinary use, flowers to cut for the home and grow a few colourful favourite plants. Plant explorers brought back new plants to try out and slowly the variety of border plants increased in range. These  can include shrubs, roses, herbaceous plants, bulbs, climbers, ground cover, and anything else that happens to be popular at the time. Often in the early years before plants get established any bare patches can be filled with bedding plants and annuals from seed sown each year.

Borders next to buildings are often designed to link the hard building structure into a soft landscape, but with minimal maintenance in mind. Evergreen ground cover including conifers, are favourite and if the ground is on a slope choose plants that can bind the soil surface to prevent erosion such as flag Iris and Shasta daisies.

Design

Borders are usually long and narrow to be viewed from the front with a solid and usually permanent backing. This may be the house wall, a fence or hedge. Although it is natural to have the taller plants at the rear and short ones at the front, try to vary this to give variety of height.

Each plant will have its own season from the Doronicums and Pulmonaria flowering in early April, Delphiniums in mid summer, to the Michaelmas Daisies in September and October. It is better to try and group plants together in their season to increase the impact, and choose plants that blend well together by height, variety of foliage shape or colour. Good combinations include flag Iris with Oriental Poppies and Pyrethrum, try day lilies with Lavender in adjacent drifts, Delphiniums and Phlox are excellent together for height and colour and at the end of the summer into autumn try Anemone Honorine Jobert with a range of Asters, (Michaelmas daisies). At ground cover height, the black grass Ophiopogon is dense enough to smother weeds and when underplanted with white snowdrops is the perfect combination for late winter.

Where ever a plant is a late starter, under plant it with early flowering bulbs such as snowdrops or crocus. Plants that have a very short season such as Pulmonaria can be mixed with Cyclamen hederifolium which begins to grow and flower in late summer and then retains its foliage all winter.

If the border is in shade or partial shade select appropriate plants such as colombines, (Aquilegia), Hostas, Trilliums, Meconopsis, Epimedium, and Primulas, Bergenia, Lamium and Persicaria for ground cover.

If the border is free standing and is not backed by a building, a hedge at the back can help to define its shape, give shelter from strong winds, add colour and give a green background to the plants when in flower.

If the back of the border is a wall or fence it could create an ideal spot for a climber to give added height.

Soil preparation and planting

Borders are often planted up in the autumn so ground preparation is normal in late summer. If the soil needs a lot of amelioration, add a fair bit of garden compost, dig it in then sow a crop of mustard in spring. Dig it in when it comes into flower but before it sets seeds.  Allow it about a month before planting so the mustard is beginning to rot down and open up the soil. Make sure the soil is firmed and raked level and water if necessary before planting. Water again after planting.

Order plants well in advance as often the more popular ones sell out quickly. Your local garden centres will stock most of your needs, but it may be necessary to go to specialist growers for the best varieties. Blackmore and Langdon in Bath specialise in Delphiniums, Phlox and Aquilegia, and Claire Austin in Shropshire specialises in hardy plants. She has some terrific varieties of flag Iris, Daylilies and Oriental Poppies. They both have websites.

Most plants display best when planted in bold drifts.

 

Border plants

These tend to be lower growing than the majority of herbaceous plants, and may not die down in winter such as border carnations and Pinks, Lavender, Rosemary, Kniphofia, Sedum and Bergenia.

They add interest in the winter months when other herbaceous plants are dormant and have died back to ground level. Many rock garden plants can be added to the front of borders to soften edges such as the Delosperma, a succulent sun loving plant packed with yellow flowers in May and grows quickly, though no higher than three inches.

Flag Iris have always been my favourite. They are so easy to grow and come in some fantastic colours, though you need to buy from the specialists to see a good range. Daylilies also have a wide range of fantastic colours that will brighten up any border.

Herbaceous plants

True herbaceous plants die down in winter, but they can grow very fast and there is always something in flower from April till the frosts come the following winter.

My season starts with the blue Pulmonaria and yellow Doronicums in April, then the Himalayan blue poppies and Euphorbias in late April or early May.

Soon there is a rush as the Peonies, Pyrethrums, flag Iris, Colombines, Campanulas, and Oriental poppies enjoy the warm weather.

As they finish, the summer flowers take centre stage with Phlox, Delphiniums, Daylilies and Geraniums.

Autumn is the time for the Michaelmas daisies, Agapanthus, Kniphofia and Anemone Honorine Jobert. Most of these plants need to be in a large group to have full impact.

Bulbs

Spring flowering snowdrops, aconites and crocus are perfect in any spare space, and even narcissus, tulips and hyacinths can be found a spot. Many drifts of low growing plants will not mind a few summer flowering lilies planted at their feet.

Maintenance

Wherever possible I tend to only grow those plants than can stand up without needing support, but some essential types such as the Delphiniums will require staking. Weeds are usually only a problem early on as once the plants grow they will soon smother out any weeds.

After three or four years some clumps will require dividing and replanting.

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