Gardening in early summer

Posted on by Lisa Firth

Gardening tips from horticulturalist Martin Howe at Wykeham Mature Plants

Photinia Red Robin spring foliage

Photinia fraseri ‘Red Robin’ is a shrub which has become extremely popular in recent years and can be used for a wide variety of situations, even trimmed as a ‘standard’ to give a tree-like shape to provide evergreen screening above a 6ft fence or wall. It is a vigorous, large-leafed evergreen, mainly grown for the bright red colour of the young leaves, which gradually mature to a glossy dark green – or should do! At this time of year, and this year in particular (after the “Beast from the East”), many people find that this shrub isn’t looking as good as it should and come to us with questions such as “My Photinia Red Robin shrubs looked fantastic when I bought them; dense with shiny dark green older leaves and bright red younger leaves. Now, a couple of years later, the young leaves still come out bright red, but the older leaves are a paler yellow-green, with dark spots on them, and the bushes as a whole look thin and straggly. Lots of the older leaves have dropped off, and many on one side have turned brown. What’s happened and what can I do to make them look healthy again?”

There are a number of factors which could be involved here. The first and easiest to explain is brown, “burnt” leaves at the top or on one side; if the Photinia is growing in an exposed position there’s a good chance that the cold storms in March and April of this year have caused some windburn. It’s quite understandable when you think about it as we had gale force winds at sub-zero temperatures, which effectively freeze-dried exposed foliage. Photinias weren’t the only evergreens to suffer as laurels, Viburnums, and even conifers may be showing brown tips, especially on the Easterly side, but after a good prune and a feed most should grow back.

Photinias don’t do particularly well in shade or in close proximity with large, established trees. When grown in the shade they tend to become drawn and rather straggly and, although like most evergreens they won’t tolerate being waterlogged for long, excessively dry locations tend to stress them, making them drop more of the older leaves than they otherwise would. Photinias will grow in a range of soil types, including quite alkaline conditions if there is sufficient organic matter, but they could be described as hungry feeders. Their natural growth habit is quite vigorous and upright, producing new leaves at the tips of long upright stems, and dropping the older leaves as they go, the result of which, if left to their own devices, is often a rather straggly shrub with “bare legs”! However, with a little bit of work every year, and it doesn’t have to be very much, these shrubs can look completely different; dense, glossy and colourful.

Sickly Photinia

Firstly, an annual trim is essential to encourage side branching and to maintain density, just as you would do for a hedge. In fact, if the site isn’t too windy, too cold or too wet, Photinias can be used to make an attractive hedge with great effect. I like to give an annual trim in June to maintain density – it breaks your heart to remove a fair proportion of the new red leaves, but a second flush will soon emerge after a few weeks which will then see you through to the autumn. Don’t trim too late in the summer or autumn as the new leaves will still be too soft when the frosts come and will be frost burnt. Restorative pruning of a leggy specimen can be done by hard-pruning to just above a bud or node, cutting quite far down the leggy stems to encourage a bushier plant, at any time between April and June, depending on how cold the weather is. Secondly, as I’ve said, they are hungry feeders, so an annual feed in April works wonders. A general fertiliser, such as Fish, Blood & Bonemeal, or a good Rose fertiliser, will make a significant difference to the appearance and colour of the foliage. If necessary, repeat this in mid-summer. Another aspect to feeding Photinias is that their vigorous nature means that they use a lot of Magnesium, a shortage of which would encourage the plant to shed yet more of the older leaves. Magnesium is a very mobile nutrient, and it is easily leached out of freely draining soils during prolonged periods of rain, and drought conditions will also affect the plant’s ability to take it up. A tablespoonful of Epsom salts dissolved in a gallon of water and applied at or soon after applying the other fertiliser will help prevent a deficiency, which would otherwise result in the plant taking Magnesium out of the older leaves to put into the new ones. Interestingly though, Magnesium deficiency symptoms in Photinias often cause little burgundy-coloured spots on the older leaves, as well as a general yellowing of the older foliage. These spots can easily be mistaken for a fungal leaf spot disease. This doesn’t of course mean that Photinias can’t be affected by leaf spot diseases, of course they can, as are most plants in some form. However, it tends to be already stressed plants that are worst affected. You can control these fungal leaf spot diseases to a point using general fungicides, such as those for spraying roses, but an otherwise healthy and well-fed Photinia will usually just shrug-off leaf spot and continue to grow happily regardless.

Being too dry for too long, or too cold in winter, are other stress factors which can also stimulate Photinias to drop more of the older leaves and thereby necessitate a one-off restorative pruning, so occasional watering in long periods of dry weather (I use the washing-up water!) will help with that potential problem, but there’s not a lot you can do about a cold winter. For this reason, due to the greater proportion of older leaves dropped in spring following a cold winter in the North of the country than our Southern cousins would experience, Photinia is not very suitable for ‘pleaching’ (fanning out on a flat panel above a tall clear stem to give a two-dimensional screen) in the North as it is difficult to maintain sufficient density to give the required effect.

This is a question that we get asked a lot, so I’ve given quite a lot of information here, but to sum up, if you want Photinias to keep their density and to look their best, trim them annually, feed them once or twice per year with a general fertiliser and some additional Magnesium, don’t let them get too dry for too long (but don’t drown them) and never plant them in the shade.

Things to do in the garden in June

Late May, or early June to be on the safe side, is the time to start planting out tender plants, including summer bedding, tomato plants and tender crops for the veggie patch such as French Beans. However, be prepared to keep an eye on the weather forecast for late frosts.

After the wet weather of last year we have been told to expect a population explosion of slugs. Protect what you can, using whatever your favourite methods of slug control may be, keep an eye out for signs of damage and act appropriately with any and all means necessary!

Weeds are growing at full pelt now. It’s a lot easier to keep on top of them by weeding little and often before they can take over than to leave the job until it becomes a mammoth task.

Most lawns will need mowing weekly by now. However, in the unlikely event of a hot dry spell raise the height of the mower blades a notch or two to help stop it from turning brown so quickly.

If planting your own hanging baskets & summer containers, always use a good compost to get the best results. To help them go a little longer between waterings add some moisture-retaining gel. A good compost should have enough nutrients for the first few weeks, but to help them keep performing for longer, either add some controlled release fertiliser pellets or start feeding regularly after about three weeks with a good tomato food.

If planting containers for the longer term, i.e. to last more than a single season, always use a soil based compost, such as John Innes no3, as most multi-purpose composts are made from peat or a peat substitute which will quickly decompose to leave a pot full of nothing but dust and starved roots.

Remember that newly planted trees and shrubs need regular watering, and hungry feeders such as Laurel and Photinia may be in need of a general feed by now, such as with Fish, Blood and Bonemeal.

Continue to sow short crops such as salad crops and beetroot.

Martin Howe is a professional Horticulturalist, currently working at Wykeham Mature Plants near Scarborough (www.wykehammatureplants.co.uk, Twitter @MaturePlants), a 150 acre nursery specialising in “instant” hedging, large trees and shrubs in sizes larger than are normally available at Garden Centres.

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