Ask the Head Gardener – July 2021
Each month we give the opportunity to ask questions of our gardeners – about the gardens at Killruddery, or gardening in general.
This month our Farm Shop Nursery Gardener, Glenn Keelan, takes the questions. Next month it’s our Head Gardener, Daragh Farren, and so on every second month.
Questions below were asked through Instagram. Any more questions? Pop them in the form below, or watch out for the monthly invitation on Instagram or Facebook.
What to do to get rid of snails and slugs? My lupins are savaged every night.
One option is calcium spray. Spraying plants with a protective calcium chloride solution seems to deter slugs and snails, while not harming any other wildlife in the process. Dedicated use can yield fantastic results, as long as you repeat applications after rain.
Copper tape is a good solution for young plants. Slugs will not move across copper, so by placing a copper ring around emerging shoots you will enable them to grow without being eaten. Bear in mind that, as the leaves grow, they may flop over the copper ring and be eaten.
Tips for a slug-free garden:
- Patrol your garden on wet evenings and hand-pick slugs and snails from your plants.
- If slugs are a huge problem in your garden, consider growing plants they don’t eat, such as Aquilegias, Penstemons, Euphorbias and Astrantias, to name a few.
- Be vigilant – the more often you control them, the fewer problems you’ll have.
- Consider digging a pond – frogs, toads and newts eat small slugs, while birds and hedgehogs will eat them, too.
Garden roses, leaves keep falling. What is the reason for this?
This is most likely due to black spot, a fungal disease. What I would advise is:
- Remove all the fallen leaves around the base of the rose.
- Improve the air circulation around your roses by spacing them properly and pruning them regularly.
- Keep the foliage as dry as possible, since the spores need a wet surface in order to germinate.
- Avoid overhead watering, or water early in the day so the foliage has time to dry before nightfall.
What could I plant for seasonal decor at Christmas?
Araucaria heterophylla (Norfolk island pine) look great as an indoor mini Christmas tree. They can be potted up in a nice terracotta or glazed pot. Poinsettias in terracotta pots look great and add a vibrant splash of red to your Christmas displays. Cyclamens are a must have for the Christmas season. They look great in the garden borders or also potted up and displayed in your home.
Any advice on natural/non chemical slug and aphid control?
For aphids, use your fingers to rub them off, or spray them with very mild soapy water, or – on sturdy plants such as roses – squirt them with a powerful jet from a hose. Birds, wasps and ladybirds will do their bit, too.
For slugs, the most obvious solution is hand picking. Slugs and snails hate bright sunshine and hot, dry weather, so the best time to find them is at night with a torch. If you have only a few plants in pots, this is an effective means of control. Take the pests somewhere else if you don’t want to kill them – but remember, they have a homing instinct, so take them for a car ride.
Please can you recommend a good peat-free compost?
A good peat-free compost is New Horizon All Plant Compost, which we supply in the Killruddery Farm Shop. Another good option is Klasmann Peat Free Potting Substrate.
Q: I live in Aberdeen, it’s very cold. Any suggestions for good flowering plants that will grow in [a cold] climate and return annually?
Daragh: There are many to choose from, and fewer limitations than you might think. Lots of the staple flowering perennials, or flowering shrubs and trees that are commonly grown all around Ireland, will grow also in Aberdeen. Of course you’ll have a contracted growing season compared with we are on the east coast of Ireland. This could extend to quite a few weeks, manifesting in a slower, later Spring, and an earlier end to growth in the Autumn. If your garden is exposed as well as cold, that will also be a consideration – cold winds can have a burning or scorching effect, particularly on young, soft, emerging growth early in the season. Another factor might be drainage / soil moisture. Often, if a plant proves challenging to sustain over winter, the cold may well be an issue, but cold and wet (around the root zone) is a lot more problematic than cold and well-drained.
Here are some examples of the kind of material I think will be okay with your very low temperatures, and with the shorter growing season. Almost all hardy Geraniums, lots of which have very lengthy flowering periods – G. ‘Rozanne’ is just one example. Anemones, especially the Japanese hybrid ones like Anemone x hybrida ‘Honorine Jobert’. This is tough as old boots and even invasive in many sites. It’s a useful plant, but choose its position with great care – I use it in a couple of spots where it can’t spread. Honestly, the list is not all that restrictive – Irises, Hellebores, Achillea, Helenium, Asters, Echinacea, Nepeta, Centaurea, Scabiosa, Geum – all good, reliable flowering perennials. As mentioned, your season will likely be noticeably shorter than what we are used to, and if concerned about winter dampness, incorporate grit and some compost in a generous planting hole – that should help your plants endure. There are some favourites that might struggle during a cold Scottish winter – I think Echium might be a challenge, and perhaps things like Osterspermums would struggle to overwinter – but you have tonnes of great options.
Here are some more. Flowering shrubs – Rhododendrons, Azaleas and Camellia come immediately to mind. Viburnums of any kind – a great genus that sometimes feels a little underrated. Hydrangeas – many options, I especially like H. quercifolia, the oak-leaved hydrangea. Deutzia, Kolkwitzia, Amelanchier, Philadelphus, and so many others. The main thing I’d watch for is good ground preparation prior to planting; not planting with overly juvenile material; and planting not too early in Spring, hopefully thereby maximising establishment in the initial growing season as the plants head into their first Winter.
Q: I’m looking for a tree with sparse branches that won’t obstruct the background too much.
Daragh: I think Birch is the best option here. They are not particularly spreading in habit, and tend not to develop a network of heavy limbs / branches. In addition, they produce small leaves and a canopy noticeably less dense than many other trees of similar popularity.
An alternative, giving an entirely different effect, might be to plant a narrow tree, roughly columnar in shape. There are various options here – consider a beautiful Oak called Quercus fastigiata ‘Koster’. It’s an easily available cultivar, widely grown. The bonus here is some pretty reasonable Autumn colour, and of course who wouldn’t want an Oak in their garden… It doesn’t possess the ‘lightness’ of a Birch, it’s a little fuller in terms of density, but its spread would be less. As Oaks go, this is a more viable option as a garden tree – it doesn’t really achieve typical Oak-like proportions.
A third option – also on the theme of fastigiate trees – would be something like an Italian cypress. Again, widely used, easy to come by, but it does strike a different tone. I see them as something not necessarily planted singly – you might use two of them to frame a view. This tree is notable for its extreme narrow, tight shape. It’s a conifer, and its very characteristic shape/ habit will certainly ensure minimal obstruction of anything in its vicinity.
Q: Could you give some advice to a first-time climbing rose grower? We planted bare roots in November and they are leafy now.
Daragh: One of the more important things to be aware of with rose growing of any kind is their hunger. Roses are vigorous growers and feeders; this is particularly so with climbing and rambling roses. I would advise a two-pronged approach to feeding, some of which you may hopefully have included when planting. Either way, good quality organic material is massively beneficial to roses. The optimum material is of course farmyard manure of some kind. Ensure it’s well rotted – if not, the acidic nature of the material will, at the very least, have a scorching effect on your plant. I would couple the use of organic matter with a granular, compound fertiliser. What this means is a pelleted type fertiliser, containing a broad mix of major and trace elements. There are numerous options here: organic or non-organic, fast- or slow-release. Any will be helpful, but be very sure not to exceed the recommended rate – it will not help the plant. A fast-release product will mean a quick breakdown of nutrients, and therefore a quick uptake by the plant. You would need to reapply later in the year.
You should also watch for weed growth around the base of the plant – anything newly planted will benefit from your ensuring minimal competition in its first season or two. Also, as your plant grows, watch for a lot of the pests and diseases we associate with roses – though many of the more recent introductions have reasonable resistance to some of these things. The most common pest are aphids (greenfly, blackfly…), while black spot is probably the most likely disease. These can be tackled using applications of a washing-up liquid or a baking soda solution respectively.
Of course, you need to train your climbing rose – it requires a ‘climbing frame’ of sorts, and will need tying in and maybe an occasional bit of nudging in terms of direction. As the branches grow, you will need to secure them to whatever you wish it to grow over. Aim over time to have a network of main branches – remember that when they’re young, they are more easily manipulated into position. Once you have a reasonable amount of growth present, don’t be afraid to remove, fully if necessary, branches that are going in the wrong direction. I would recommend pieces of soft string or coated wire for tying in. Do this as required especially over the plant’s formative years.
Q: Can you suggest good evergreen trees for a small garden?
Daragh: So many possibilities. My first suggestion would be Luma apicualata. It’s native to Chile and doesn’t tend to get very big at all here. Though hardy, it can suffer a little in drying winds, and may develop the odd scar or two in an especially cold winter. This is a classy plant though, one I have in my own garden – small, glossy, dark green leaves, lots of tiny white flowers, little black berries, and above all, the beautiful orangey/tan-coloured, exceptionally smooth bark. In fact, we have quite a few in Killruddery, and I’ve seen it for sale in the Farm Shop.
Arbutus unedo is a good candidate – ignore the size of the one in Killruddery: it is, for various reasons, entirely atypical of how this tree will usually grow. The Arbutus unedo, or the Killarney Strawberry tree, occurs rather oddly in an area of Portugal and the Southwest of Ireland. Again, one of its finest characteristics is found in the bark – a beautiful, peeling brown – but there are also the strawberry-like fruits that arrive, usually along with white flowers, in autumn. The fruit is edible but not pleasant – birds however will happily avail of them. Often quite a spreading tree, and tolerant of a wide range of conditions.
You could also opt for something quite different– maybe a fastigiate yew or a clipped holly or osmanthus. Here you will get your evergreen tree, but also incorporate a bit of formality and structure – even if formality in your garden isn’t your aim, you could produce a nice contrast by using light, airy material in the immediate vicinity of a clipped specimen – perhaps some ornamental grasses, or tall flowering perennials.
A couple of others that may be worth some further investigation: some of the Ceanothus – more a large shrub, but really spectacular around May, clothed in brilliant blue flowers. Bay – Laurus nobilis might be an option, and you have the culinary uses and berries later on. Various conifers other than yew – I’d like something unusual and a little special like a wollemia – a great story with that one, which I’ll tell next time I do a garden tour.
Q: Best time of year to take clippings from perennials? How do you propagate rosemary plants?
Daragh: I’m assuming this question relates entirely to propagation. The best method of propagation, or the best time to take cuttings, is very species-dependent. Most perennials are probably best divided, though plenty can also be increased by cuttings. Briefly, division is generally carried out in either autumn or spring, and is often quite straightforward, and will pretty much always (if successful) produce a good-sized, flowering plant very quickly.
However, to propagate perennials by cuttings is, as mentioned, a question of species and timing. The real consideration is the material you will use, and whether it’s present and available in a condition conducive to forming root. It’s perhaps best to give some specific examples of things I’ve done recently.
A week or two ago I took very small stem cuttings from Achillea. These are the very start of the new shoots arising from the base of the clump – just coming out of its winter dormancy. I’ll do some soon from some of the sub shrubby salvias, also using the youngest, newest of shoots, coming from ground level. These are very soft cuttings, full of pent up growth and vigour. Cuttings of suitable material (and species) of this kind usually root quickly, but can be a little delicate prior to that, mostly due to their softness and general condition.
Soon, I’ll pot on some rooted perennial cuttings I took around last July – lots of Sedum spectabile. Those cuttings, soon enough after being taken, would have evidently disappeared – the herbaceous nature of the subject – but have in recent weeks produced buds and broken the surface of the rooting media, just as the plant might behave in the open ground… my rooted sedums are ready for potting.
So, the question of successful propagation methods is very dependent on the subject. More often, with regard to perennials as opposed to woody plants, I would opt for divisions (or maybe seed) rather than cuttings.
As far as rosemary is concerned: I’ve always taken cuttings in mid to late summer – around July or August. These would be considered semi-ripe or ripe cuttings, you’re using this year’s material. Try to select a soft piece of stem with no flower – not always easy with rosemary. If no such material exists, remove the flowers. I take quite short cuttings with rosemary, I suppose no more than 6cm or so. Remove the lower leaves – this must be done very carefully with rosemary in particular – it’s very easy to create tiny tears in the stem tissue that are almost unnoticeable, but will greatly increase the chance of rot. Rotting can be a big problem for cuttings. The cuttings are then inserted in compost or a free-draining media – don’t overcrowd – maybe three cuttings in a small, round 9cm pot. Water or mist, and then cover with plastic (or fit a polythene bag over the pot), leaving in a sheltered area, or a shaded part of a glasshouse of cold frame. Hopefully, rooting will take place over the coming weeks. I would caution against potting too early – don’t be afraid to wait till spring if need be. Also remember a nice well-drained compost when you pot – rosemary will resent too much moisture, especially when young.
Q: How long does it take to mow the grass?
Daragh: This depends on time of year, general conditions, and the specific area in question. The type of maintenance regime for a particular area will have a bearing too – we have a range of methods we use in differing areas, for a variety of reasons, all of which have an influence. To date, we’ve done a couple of cuts everywhere now – it could definitely have been started earlier but we wanted to channel our time elsewhere. In an average year, whatever that is, assuming relatively typical heat and rainfall (again, a bit arbitrary), I would expect grass growth and maintenance to peak from May to July. We would then be mowing certain areas twice weekly, others weekly. Often, by early August, we will have seen a noticeable reduction in growth, and quite often a little bit of an increase during September – usually coinciding with an increase in rainfall, and a slight drop in temperature. We probably would have ceased most mowing by November, having spaced out the intervals up to that point.
Q: Why do you carry walkie-talkies?
Daragh: We are in very frequent contact with one another throughout the day, for numerous reasons – mostly operational, work-related conversations, sometimes regarding issues of safety or other concerns. Although, we tend not to do this via walkie-talkies anymore – they do have some advantages, but we usually use phones.
Q: What is your favourite part of the Garden?
Daragh: It may depend a little on time of year, but overall I might opt for the Rockwood. There are a lot of plants I really like up there. I would also mention some parts of the car park, which must seem really odd. I am, however, really fond of some of the planting around there, and some of the combinations.
Q: Which season do you like the most?
Daragh: For me it’s always been spring. So much hope, potential and promise. Growth is fresh and vibrant everywhere, and neither the garden nor I yet showing the wear and tear of a busy season. Summer of course has lots of nice aspects to it, and I’ve come to love autumn very much in recent years. In our job, and in Ireland, you really do get the seasons, and the enjoyment of their differences and the pros and cons of each. It’s something I appreciate and value greatly – I feel everyone should try to have as much awareness as possible of the seasons and their nuances – in terms of plants, wildlife and everything else.
Daragh Farren – March 2021