Plant Pharmacy

Plant Pharmacy and Q&As

Advice, advice, and more advice... plus the answers to our most frequently asked questions.

1. Why won't my wisteria flower?

This has to be one of the most common questions we are asked here at Burford, particularly as the wisteria's spectacular blooms are the perfect adornment for the front of a Cotswold stone home.

First, it must be said that young wisteria are slow to flower, and it is perfectly normal to have to wait two to three years from planting before those first blooms start to reliably appear in late spring. Siting, feeding and watering correctly, and pruning are the keys to success. First, make sure you plant your wisteria where it will get as much sun as possible. South or west facing is best. Ensure you feed wisteria with a phosphate-rich feed regularly throughout the growing season to encourage blooms. Do not use nitrogen feeds or manure mulches, as this will only encourage prolific foliage growth.

Water is critical too, particularly in the dry soil you usually get against your house wall. Wisteria flower buds start to develop in the late summer of the previous year, so make sure you water adequately in July and August and do not allow the ground to dry out.

Finally, prune wisteria in two phases. Cut back the green shoots of the current year's growth in July or August (never before). You want to cut back to keep five or six leaves on the shoots, being careful not to cut off any newly formed flower buds. Then in January or February, cut back the same shoots to two or three buds. This will allow as much sunlight as possible to get to the flower when your wisteria comes back into leaf.

2. My shrub won't flower, what am I doing wrong?

We always point out that not all shrubs are meant to flower! Generally speaking, though, rather like a sulky teenager, a shrub will be reluctant to do its stuff if it is not being fed correctly, or if you give it a haircut at the wrong time of year.

Position is critical as with most plants. Lack of light or poor growing conditions will inevitably lead to weaker performance, as will planting shrubs too close together so they have to compete. Prune any overhanging deciduous trees to raise the canopy and let in more light for underplanted shrubs.

Choose your fertiliser carefully. Nitrogen-rich feeds or manures will encourage leaf growth at the expense of flowers, whereas sulphate of potash, and a covering of leaf mould or general purpose compost, will be far more helpful.

Pay attention to pruning too. It may be tempting to cut back shrubs as part of your autumn tidy-up, but remember that an awful lot of shrubs produce next year's flower buds in the autumn. As a general rule, spring flowering shrubs should be pruned immediately after flowering, whereas summer flowering shrubs (those that bloom from July onwards) should be left and pruned only in the dormant season, or just before spring growth starts.

3. My hedge has gone spindly at the bottom, what can I do?

There are a few reasons why this can happen, but the first thing to check is if there is any competing vegetation at the foot of the hedge. Brambles, nettles and perennial weeds, along with ivies and ground elder, have a habit of finding their way into the soil at the base of a hedge, and you will need to roll up your sleeves and remove these. Once clear of undesirables, add a layer of mulch a couple of centimetres deep, to suppress weed growth, help retain moisture and gently feed your hedge.

Once you have done this, turn your attention to the top of your hedge. Main shoots are always dominant over side shoots, so a decent cut back will encourage stronger side shoots and a plumper, fuller hedge. If you have a particularly spindly hedge, don't be frightened of being quite radical and cut it back to a foot or two above the ground, gradually building it back up as you wish over the following few seasons.

4. What type of compost do I need for my pots?

The answer to this does depend on what you are planting in the pots, but as a starting point always make sure you have adequate drainage at the base of the pot. Old crocks and gravel will do, making sure water can escape freely through the drainage hole.

For roses, climbers and most shrubs (let's call this permanent planting) we always recommend a 50:50 mixture of a soil-based John Innes compost and general purpose, peat-free compost. Combine with a handful or two of slow release feed pellets and mix thoroughly before planting. Top up (called top dressing the pot) annually.

For more showy annuals and containers you want to be overflowing with seasonal flowers, choose a specific bedding/multipurpose compost with moisture control and added nutrients.

When growing beans or tomatoes in a container, try to choose a compost with high levels of potassium to encourage a higher yield. By the way, don't be tempted to reuse multipurpose composts from one season to the next. Chuck it on the compost heap, and start afresh each season.

If you are planting any lime-hating plants, such as camellia, azalea, rhododendron or blueberries, always use specific ericaceous composts. Other acid-loving plants such as Japanese maples and skimmia, although tolerant of alkaline soils, will generally prefer ericaceous composts too.

5. How often will a plant need watering?

Well, the unhelpful answer is, that depends. As a rule, ensure newly planted plants out in the garden are watered well in their first year, particularly during the summer months. After the first year they will have established their roots and should be better able to fend for themselves, except in periods of drought.

Pots and containers must be watered daily, if not twice daily during the summer and late spring. The vegetable and salad garden will need close attention too, particularly during the early growing season. Water this daily in dry weather, but ease off a couple of weeks before harvest time.

Keep an eye on shrubs and climbers planted up against the house. Overhanging eaves often create a dry zone beneath, and a weekly dose of water in summer will help maintain your plants in tip-top condition.

6. How can I get rid of slugs?

Well, the correct answer is perhaps you shouldn't, and in fact you can't ever rid your garden of slugs.

A slug's job is to eat decaying matter, leaves and vegetation. They are also an invaluable source of food for garden friendly wildlife, particularly hedgehogs and thrushes.

Attempt deterring them first. Slugs are attracted to the soft tissue of young plants and seedlings, so try encircling these with copper (which give slugs a mild electric shock), coarse bark, bran or even spent coffee grounds, none of which they like to cross.

If you are still bent on killing these slimy gastropods, do so kindly. Create a 'slug pub' by placing cleaned, empty yoghurt pots into the soil and pouring in a decent amount of beer. This attracts them in, and they fall in. Alternatively, choose an environmentally friendly slug killer, such as Neudorrf®'s Sluggo, also certified for organic use.

7. What can I plant in dry shade?

Our first choice would always be evergreen epimediums. Spring flowering, these discreet plants have particularly attractive leaves and, once established, need almost no care. Euphorbia robbiae (above), dusky cranesbill Geranium phaeum and the stunning, creeping dead nettle Lamium are also excellent choices, adding colour and seasonal interest.

8. How can I get rid of ground elder?

Quite possibly one of the worst common weeds in the garden, once it has established it is extremely difficult to eradicate. It worms its way in everywhere, through plants, between plants and under plants.

If you can lift your prized plants out of the border temporarily, you can try your hand at digging ground elder out. Remember though that one tiny fragment of ground elder root left in will quickly form a brand new, quick spreading plant, and you will find yourself back to square one within a year.

We have only ever used weedkillers very sparingly, but with ground elder we may make an exception. Cover up your plants with polythene to avoid spray drift, and soak the leaves and stems of growing ground elder with a tough glyphosate weedkiller, such as a tree stump and root killer. You may need to repeat the process two or three times, but it should knock out ground elder.

9. When do I need to prune a climbing rose?

The Generous Gardener Climbing Rose

Generally speaking, a climbing rose should be pruned in winter, after all flowers have faded. December to February is best, removing all dead, diseased or weak shoots, and cutting back any flowering shoots to a third of their length.

However, is your climbing rose in fact a rambling rose? If so, prune in late summer or autumn. We generally recommend removing one in three of the oldest stems entirely every year, right to their base. As with climbers, cut back side shoots to a third of their length.

10. I always seem to kill my houseplants, are there any foolproof ones?

Most houseplants will need at least a little care, and all will benefit from being placed in the right position in the home.

In terms of 'foolproof' houseplants, succulents are probably as close as you can get. Banish from your mind the 1970s image of dusty prickly cactuses lined up on a bedroom windowsill – succulents are now very much in vogue. There is a vast array of stunning shapes, colours and sizes available, from soft silvers, to verdant greens and deep russet reds, with which you can create beautiful patterns and layered textures to suit your taste. Succulents will always prefer a bright spot, but will need minimal attention and negligible watering, and repotting only occasionally, once they have outgrown the pot.

Callicarpa profusion burford favourite

Callicarpa bodinieri profusion agm

Callicarpa bodinieri Profusion AGM

This gorgeous plant has outstanding autumn colour, and berries that last until early December.

It fruits well on its own, with large packed clusters of the berries in mid-autumn, overlapping with the golden purple leaf tints, lingering after leaf-fall. Ideal to place in vases, particularly when the bare branches are laden with berries, it was given the prestigious Award of Garden Merit (AGM) by The Royal Horticultural Society.

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