October 2024 - ‘Autumn in all its Glory’
In October autumn closes in on the garden and the winter beyond comes into focus as the growing season draws to a close but what a glorious closing it is! Autumn gardens never need to be dull with such a wide range of colourful, late flowering perennials to choose from in addition to autumn flowering bulbs and all the leaves and berries of trees, shrubs and climbers.
In terms of past October blogs, in 2020 I started by looking at some of the science behind the autumn leaf colours. Basically, the plants react to shorter days and lower temperatures, particularly at night, by starting to break down the chlorophyll in their leaves that enables them to photosynthesise the sun’s energy to produce materials such as cellulose, starch and sugars. The chemicals in the chlorophyll are broken down into simpler forms and moved into the main branches, trunk and roots to be stored safely through the winter and to be available for recycling in the following spring. As the green leaf pigment of chlorophyll is removed the other leaf pigments become apparent and begin to reveal their own colours- carotenes and xanthephylls produce yellows and oranges while anthocyanins and any remaining sugars produce the reds and purples. This 2020 blog went on to list lots of wonderful autumn trees, shrubs, climbers and perennials which between them produce glorious leaf colour, berries or flowers at this time of year. The October 2021 came from Aberglasney and in 2022 I was writing about trees in general and apple trees in particular. In 2023 the blog was about creating structure in the garden using both hard/non-living and soft/living landscaping features and was illustrated by reference to a major garden, Aberglasney, and a much more modest one, ours in West Wales!
As for my ‘five October plants which I wouldn’t want to be without’, I could actually still choose several of those that I have opted for over the last few months as they are still performing well- at least at the beginning of the month- such as Hydrangea, Sedum, Rudbeckia and Helianthus ‘Lemon Queen’. So for this month I have gone for some, perhaps less well known plants, two of which are shrubs. Caryopteris is a lovely, deciduous shrub which with its blue flowers, always a winner in my eyes, comes into its own in the autumn. The most widely grown plants are cultivars of C. x clandonensis all of which have lance-shaped, slightly toothed, grey-green leaves which are silver-hairy beneath and blue or purple-blue flowers in terminal clusters. ‘Kew Blue’ has dark green leaves above and silver-grey beneath with dark blue flowers, ‘Worcester Gold’ has warm yellow foliage and lavender blue flowers and ‘Heavenly Blue’ is a more erect plant with intensely dark blue flowers. They all do best in a sunny position and apart from a light prune back to live wood in spring require little attention. Pittosporum tenuifolium ‘Tom Thumb’ is a real favourite of mine as it gives me a small, rounded, evergreen shrub as well as dark foliage of flushed bronze-purple which provides a great foil for flowering plants around it. We give our plant a light trim in spring to remove any winter damage and to control its size after which it produces a new set of green leaves which then turn bronze-purple over the following months.
Caryopteris ‘Heavenly Blue’ // Pittosporum tenuifolium ‘Tom Thumb’
My next two choices are herbaceous perennials, both of which do well for us in our sunny, well-drained, gravel garden. The first is Verbena officinalis ‘Bampton’ which has striking, purple-tinted foliage and sprays of lavender-pink flowers with purple stems all summer and well into autumn. Like a lot of Verbenas its small flower clusters, small leaves and long stems gives it a very light and airy appearance. Interestingly, Verbenas belong to the same family as Caryopteris, Verbenaceae, as a closer look at their foliage, stems and flowers will confirm. My other herbaceous perennial is Calamintha nepeta, the Lesser Calamint, a member of the Labiatae (Nettle) family. This is a low-growing perennial with small, ovate, toothed, hairy, dark green leaves and mauve to pink flowers on branched flower spikes in summer and autumn- much loved by bees but left alone by cats! Like the Verbena it gives a light and airy feel to the planting and doesn’t dominate in any way.
Verbena officinalis ‘Bampton’ // Calamintha nepeta
My fifth choice is more unusual in that it is a plant which graces our garden over many months and doesn’t really have a time when it takes centre stage. Nevertheless, I can’t imagine a garden in our part of the country without its fair share of lovely ferns. These are very primitive plants that produce unusual leaf structures known as fronds. They belong to a group of plants that lack flowers and that reproduce from spores rather than from seeds. They can be either epiphytic (lodging on trees or rocks) or terrestrial (rooted in soil). Some are evergreen, others deciduous, some such as Matteuccia and Osmunda prefer damp soil while others such as Asplenium, Polypodium and Polystichum also do well in damp conditions but can tolerate relatively dry sites as long as they are also shady. They also come in a variety of sizes (we have one which exceeds 4ft/1.2m in height and spread and another, an Asplenium I think, which is only a few inches/cms in height and spread, as well as in different shades of green and forms of frond. Most of ours have arrived as if by magic and on the whole, they are most welcome. The evergreen ones we simply tidy up in spring by removing the old, often winter damaged fronds. This is particularly necessary with the Hart’s Tongue Fern, Asplenium scolopendrium, which crops up all around the garden often in cracks, crevices and dark places where other plants won’t flourish. For deciduous species we leave the frond on the plants through the winter unless they are bent, broken or lying on neighbouring plants and simply remove them in spring just before or as the new fronds literally erupt from the base of the plant.
Our ‘Little and Large’ Ferns
Last month we looked at the naming of plants using the binomial system devised by Carl Linnaeus in the 18th century which uses Latin terms to describe both the genus and the species of plants. However, as even a brief look around any garden centre will confirm, for many plants just two names are not enough to uniquely identify them. This is because within a species there can be variations which require those plants to be separately identified. These variations either occur naturally through the cross fertilisation by natural means or by the deliberate breeding of plants by humans in an attempt to produce better or more attractive varieties. Those that occur naturally are known as ‘varieties’ and those bred by humans as ‘cultivars’ (cultivated varieties). Varieties are written using a small initial letter and in italics like the genus and species names whereas cultivar names start with a capital letter, are enclosed in single quotation marks but are not written in italics. For example, Fagus sylvatica purpurea is the naturally occurring variety of Beech and Erica carnea ‘Vivellii’ is a cultivated variety of Heather. Another way in which plant names are sometimes written especially when referring to fruit and vegetable plants is a combination of common name and cultivar name eg. Raspberry ‘Glen Clova’ and Potato ‘Majestic’. There are also some plants, known as hybrids, which are produced by sexual reproduction, either naturally or by human intervention, between different species or even different genera although this is quite rare for the former and even more rare for the latter. When this occurs a new species or new genera is created and a special method is used to indicate this within the name. A plant that is a hybrid between two species has an ‘x’ placed in front of the species name eg. Magnolia x soulangeana (a cross between M. denudata and M. liliflora) and Anemone x hybrida (a cross between A. hupehensis japonica and A. vitifolia). A plant that is a hybrid between two different genera has an ‘x’ placed in front of the genus name eg. x Cupressocyparis leylandii (a cross between the genera Cupressus and Chamaecyparis) and x Osmaria burkwoodii (a cross between Osmanthus and Phillyrea). Finally, it is worth mentioning that as in all classifications there are many levels and the one immediately above genus is ‘family’. However, as the family name is not necessary to make the plant name unique it is not written as part of the plant name and for the horticulturalist/gardener is of much less importance than the genus and species names.
As we approach late autumn and the beginning of winter we also get to the time of year to think about the last of our techniques for taking cuttings. Hardwood or ripewood cuttings are taken from mature wood of both deciduous and evergreen plants at the end of the growing season from autumn through to spring. It is a method which can be used on a variety of plants including shrubs, roses, climbers, trees and fruits. As the roots develop slowly over a long period the cuttings need to be longer than for the other types of cutting to provide them with larger food reserves. They also differ from other stem cuttings in that they can be rooted either in large pots in a cold frame or into the open ground. The cuttings need to be around pencil thickness and taken from the current season’s growth just above the previous year’s growth. Each cutting should be around 6”/15cm long and cut at the top just above a bud or pair of buds and at the bottom just below a bud or pair of buds. For evergreens the cuts are made just above and below leaves. The leaves in the bottom 4”/10cm are then removed and any large leaves left at the top can be cut in half to reduce moisture loss. The basal cuts are worth treating with a hormone rooting compound and then the cuttings can be placed in pots of well drained potting compost about 4”/10cm apart leaving 1-2”/2.5-5cm of the cuttings above soil level. Alternatively, the cuttings can be planted in the open ground in a prepared nursery bed by opening a slit with a spade, adding some sand to its base, planting the cuttings around 6”/15cm apart and closing the slit with the boot. Cuttings in pots in a cold frame will normally root by the following spring but those in the ground should be left in place until the following autumn and then potted up or transplanted to their permanent positions. In terms of shrubs this method works well for Aucuba japonica (Spotted Laurel), Buddleja, Buxus, Cornus alba and C. stolonifera, Deutzia, Forsythia, Hypericum, Ligustrum, Philadelphus, Ribes, Rosa rugosa and other roses closely related to wild species such as ramblers, Rubus, Salix, Sambucus, Spiraea, Tamarix, Viburnum and Weigela. Most climbers are best propagated from semi-ripe cuttings but some such as Actinidia kolomitka (with its pink and green leaves), Bougainvillea, some Honeysuckles, Parthenocissus and Vitis do well using the hardwood method. Most trees propagate best from either softwood or semi-ripe cuttings but some can be successfully grown from hardwood cuttings including Ficus, Metasequoia glyptostroboides (Dawn Redwood), Morus, Platanus, Populus and Salix. For fruit propagation hardwood cuttings are generally successful for figs, vines, currants and gooseberries.
At this time of year we are also approaching the time to plant bare root trees, shrubs and hedging. This can be done at any time during the plants’ dormant season ie. November through to the end of February but current thinking seems to be that getting the plants in before Christmas give them more time to develop good root systems before their first summer after transplanting. It is also generally true that the soil is easier and drier to work on in the late autumn and early winter. The two great advantages of bare root plants over container grown plants are that the former are much cheaper which is particularly important if large numbers of plants are needed for a hedge. Bare root plants are also known to establish more quickly as they are used to being in the ground and as such won’t have developed the circular root growth which container grown plants do especially if left in their pots for too long. The roots of bare root plants once lifted from their nursery beds need to be kept moist, preferably ‘heeled’ into some old compost or a vegetable bed. It is also a good idea to give the roots a soak in a bucket of water immediately prior to planting. Any damaged roots should be cut off back to healthy growth and the tree or shrub (or indeed Wallflower) planted at the same depth as it was originally ie. with all the roots covered but not so deep that the bark just above the highest roots is covered in soil. On poor soil it is always a good idea to improve the soil before planting by adding organic matter and a slow-release fertiliser such as bonemeal. On good soil or once the soil has been prepared planting really just involves opening up a slit with the spade, placing the plant with its roots spread at the correct depth and closing the slit with the boot. For trees with a larger root mass it may be necessary to dig a suitable hole before placing the tree and backfilling with improved soil, firming with the boot and adding a stake for support over the first few years. To finish off a good watering in and the addition of some sort of organic mulch is always a good idea, as is giving the plants a slow-release fertiliser in the spring and paying attention to watering in the summer of the first year.
Finally, I’m sure that I make this plea every autumn so forgive me if you have heard or read this before. There is a truly wonderful, completely natural and free soil conditioner/improver which we can all start to make at this time of year- leaf mould. Most gardens have leaves which fall on lawns, into ponds, onto paths, patios and drives and indeed precious plants which for various reasons need to be cleared away. In the natural world these would fall to the woodland floor to become leaf litter and over time be incorporated into the soil and break down to release all the valuable materials which they consist of. This is a vital part of nature’s recycling system which maintains the soil’s fertility, texture and structure and ensures the continued health and growth of the plants above. To some extent this still works in our gardens in the spaces between and beneath plants but such a valuable resource is surely too good to waste by just disposing of any collected leaves. Small amounts can be added to and mixed into the compost heap or bin but larger amounts need to be dealt with in a different way. This is because in a compost bin it is bacteria which breaks down the organic matter generating heat as it does so whereas leaves are broken down by fungi in cool, damp conditions over a longer period. For most gardens with limited space the best method is to put moist leaves into black plastic bags with a few holes pierced in the base for drainage and tied at the top. These can be left in out of sight places until the leaf mould is ready. Usually after one year leaves will still be recognisable but even at this stage the leaf mould is usable for mulching and general soil improvement. After another year though if you are prepared to wait that long the leaves will have broken down completely to form a black, crumbly substance which smells of the woodland floor which is a fantastic addition to potting composts for all sorts of purposes by providing some plant nutrients, vital trace elements and food for beneficial soil organisms as well as water and nutrient holding properties.
Well, that’s all for this year in terms of talks although I will continue to write the monthly blog over the winter months. All being well, as my mother used to say, the Saturday morning talks will resume in March next year and I look forward to seeing you all again then. I intend to invite you to bring more of your own special plants in for others to see and learn about, to encourage you to offer plants and seeds to other members of the group and to devote more time to your questions either ones on the day or others from a previous talk or email contact in advance.
Enjoy your autumn gardens and take pleasure in this very special time of year.
Keith.