The September Garden 2020

September is certainly one of my favourite months in the garden as the heat from the summer (perhaps not this year though!) gives way to the fresher air of the early autumn. It is also a time for the gathering the fruits and vegetables of earlier labours and to glimpse the first signs of the changing of the colours that the later autumn will bring. By September days are shortening and there is an increasing chance of chilly mornings with dews on the lawns and it really does begin to feel like the season of ‘mists and mellow fruitfulness’. Having said that, days in September can be gloriously sunny and with rainfall totals usually on the increase after the summer lawns start turning green again and flowering plants are encouraged to keep on producing colour and interest.

In the ornamental garden September sees the splendour of the true autumn specialists such as Aster, Rudbeckia and Sedum but it is also graced by many of the summer flowering plants which are continuing to do well. In our garden the Hydrangeas are still full of colour and the Helianthus ‘Lemon Queen’, although a little battered by the strong winds towards the end of August, is still full of its sunny, yellow flowers.

We also have Roses in flower and the large hips on the Rosa rugosa are colouring up well. The annual Cosmos and Antirrhynum are still flowering strongly as are the herbaceous Monarda and Lobelia in the borders and the tender perennials on the patio. Also at the risk of repeating myself I have to add that at the beginning of the month there are also at least nine different hardy Geraniums in flower.

I mentioned in August that one of the flowers we would normally see at its best in September, the Japanese Anemone, had started to flower early but they still have plenty of flower buds to open and even when they have finished flowering they will still have their attractive seed heads held on strong, wiry stems. We leave these on as long as they are still standing upright which is often into winter. I must admit though that once the leaves have lost their colour they can look a little unsightly and we do remove these to leave the bare stems with their ‘button’ seed heads. One other plant which is also looking good this month is the tall and elegant Verbena bonariensis from South America. In the past we have bought a few plug plants, grown them on and then dotted them around the borders to come up through and above the other plants. This year we sowed seed and as a result had a lot more plants which are now giving a dramatic show. The flower heads are fairly small and are made up of many lilac-purple florets carried on strong stems which don’t need support and the whole plant gives a very airy feel to any planting scheme. Another plant which I haven’t mentioned before which has actually been in flower since May and is still looking as good as ever  is Persicaria affinis  which we grow in our gravel bed on quite poor, stony soil. It is a bit of a spreader but is easy to control if you wish to and is full of upright spikes of pink flowers in various shades held above dark green, lance shaped leaves. Some cultivars are evergreen or at least semi-evergreen but I must admit that ours looks a bit brown and dead in the winter which is when we trim it back but it more than makes up for this throughout the rest of the year and the fact that it is part of the dreaded Dock family doesn’t detract from its beauty and usefulness as a ground cover plant for sunny sites on poor soils.

 With regard to the September ‘stars’ I feel that I must start with the wonderful Aster which my wife, Teresa always refers to as the ‘September Flower’. Actually I shouldn’t really call them Asters anymore as the genus has been divided up by the powers that be into several new genera- all for the sake of correctness and simplicity! Basically the plants which are generally known as Michaelmas Daisies which were Aster novi-belgii (New York Aster) and A. novi-angliae(New England Aster) are now called Symphyotrichum! I’m sure you will see this new name on the plant labels but I also have a feeling that most nurseries and garden centres will still be using the old name for some time to come, I know I shall! Whatever they are called they still remain beautiful plants for the early autumn and although they may be considered a little old fashioned by some they are worthy of their place in the September garden with their numerous, daisy-like flowers with outer ray-florets in a variety of colours from white, through the whole range of pinks to lilacs, blues and purples and usually yellow inner disc-florets. Some of the older varieties can get quite large and are best for the back or middle of borders but some more recently introduced cultivars such as the ‘Island Series’ are much more compact and are suitable for the front of the border or even for pots. If your plants have suffered from powdery mildew in the past then it is worth avoiding the novi-belgii cultivars as they are much more prone to the disease. There are so many species and cultivars to choose from but if I had to choose just one it would be Aster x frikartii ‘Monch’ which I believe for some reason has retained the Aster name. It has lovely, long-lasting, lavender-blue flower heads with orange centres held on strong stems up to 2 feet or so high (30-60 cms) and as a bonus I have never known it to suffer from mildew. If you like the taller, older varieties and struggle to find them there is a wonderful garden near the Malvern Hills, the Picton Garden, which specialises in them and a visit, in normal times at least, in September and October is well worth it.

There may not be as many varieties of Rudbeckia (Coneflower) as Asters but the few that are available pack a powerful punch in the September garden with their bright yellow, orange and even red petals. The flower shape is similar to that of the Aster as they are both in the same family of Asteraceae but the individual flowers tend to be much larger. The one most often for sale in garden centres is Rudbeckia fulgida var. sullivantii  ‘Goldsturm’ as it is so reliable and eye-catching with its large yellow-golden flower heads so don’t be put off by its mouthful of a name! If you ever see the variety R. fulgida var. deamii my advice would be to buy it as it is so free-flowering and for some reason you won’t come across it very often. Perhaps even more impressive because of its size is       R. ‘Herbstonne’ (sometimes labelled as R. ‘Autumn Sun’) which is up to 6 feet high (1.8 metres) with 4-5 inches across (10-13 cms) bright yellow flowers with green centres. All of these Rudbeckias are reliable perennials but there are also some less hardy species which are grown as annuals including cultivars of R. hirta.

  My third September ‘specialists’ are the clump forming Sedums, often referred to as Ice Plants. Sedums come in many forms and most are mat-forming, succulent evergreens which are great for rock gardens and gravel areas but the larger, clump forming species and cultivars really come into their own in the autumn. Most are cultivars of Sedum spectabile, the true Ice Plant. The most popular is probably S. spectabile ‘Brilliant’ which really does live up to its name with its grey-green succulent leaves and many small, star-shaped pink flowers making up large, flattish flower heads which are a real magnet for bees and butterflies. Another clump former is S. telephium with              S. telephium subsp. maximum ‘Atropurpureum’ being particularly attractive with its dark purple leaves and pink flowers with orange centres. My first choice though would always be S. ‘Autumn Joy’ (sometimes labelled as S. ‘Herbstfreude’) with its flat flower heads made up of many star-shaped flowers which start off deep pink and then turn through pinkish-bronze to copper-red. S. ‘Ruby Glow’ is similar but lower growing. One problem with the larger clump forming Sedums is that the stems do tend to flop over leaving a bare centre. This is sometimes because of the sheer weight of the flower heads but it can also be because if shaded they get drawn to the light and produce leggy and weaker stems. Growing them in a sunnier spot or using supports will overcome the problem but there is another way of keeping them more compact which is usually referred to as the ‘Chelsea Chop’ as it needs to be done at the time of the Chelsea Flower Show in late May. If the tops of the shoots are cut off at this time the plants become much bushier and sturdier later in the season even though they will flower a little later. Some gardeners just cut the front part of the plant to extend the flowering period. The ‘chop’ is also a good technique to use on other herbaceous perennials which are prone to produce long, single stems which don’t support themselves very well.

I always think that September is a really pleasant month for working in the garden, not too hot and not too cold, which is a good thing as there is still plenty to do and a full list is given in the blog archive as usual. This month marks the beginning of a very good planting time for many types of plant as the soil is still warm and moist but not waterlogged so that roots can become established before winter sets in and plants can get off to a good start in the spring and will need less, or no, watering next summer. So through September and October why not think about adding new container grown trees, shrubs, climbers and herbaceous plants to your gardens? Established herbaceous perennials can also be divided at this time and it is a particularly good time to lift and move evergreen shrubs, something which can’t really be done again until next April. If you do lift an evergreen shrub just try to get as large a root ball as possible and trim off any damaged root ends. Transferring the lifted plant onto a large sheet always helps in the movement from old position to new. Also dig a large enough hole to allow the roots room to spread out and always plant at the same depth as before. In very windy sites and with large shrubs it may be worth staking or even erecting some form of wind barrier on the windward side. Deciduous trees and shrubs are normally moved later in the year after they have dropped their leaves and become dormant and that is also the time, November through to the end of February, to plant bare-rooted trees and roses. September also marks the start of the planting time for all the spring flowering bulbs with the exception of Tulips. These are better planted in November when the soil is colder as earlier planting in a warm soil can lead to problems with the fungal disease Tulip Fire. If you are anything like us with spring bulbs you get to the point in the garden when you try to plant new bulbs and find yourself digging up some bulbs that are already there! We get around this by growing the new bulbs in pots on the patio using mainly dwarf varieties. After flowering the pots can be put into an out of the way corner for the foliage to die down naturally before returning to the patio the following spring- but don’t forget to label the pots! September is also a good time to start thinking about planting up containers for autumn, winter and spring displays. Of course spring flowering bulbs can form part of these displays but for autumn and winter interest there are lots of evergreen plants which can be used to form the backdrop for the flowering plants such as Pansy and Viola. The Old Railway Line offers a great range of these evergreens at very reasonable prices in their ‘Tub and Basket’ range.

We shall also be spending some time in September working on the lawn. If it wasn’t done in spring one of the autumn jobs, which also provides a very good fitness workout unless you have a machine to do the job for you, is to scarify the lawn. This removes the ‘thatch’, the layer of dead grass and probably some moss which builds up over time and restricts air and water movement often leading to the growth of less grass and more moss! I am always amazed at how much thatch comes out of the lawn which in some way is satisfying as it shows you that the job really needed doing. I also have to warn you that the lawn will look worse before it looks better but after a couple of cuts and some rain it will recover well. The next job, again if it wasn’t done in the spring or if the lawn had heavy traffic over the summer, is to aerate it which most people do with the tines of a fork to a depth of 3-6”. This works a whole new set of muscles so you will either be fit by the end or a wreck! Aeration allows both air and water to penetrate more easily and greatly improves the health and vigour of the grass. Especially on heavy soils it is always a good idea to top dress the lawn following aeration both to improve soil structure and fertility and to keep the holes from closing up again. The dressing can be a special mix from the garden centre or your own mix of 3 parts sieved topsoil, 2 parts sharp sand and 1 part sieved garden compost or old potting compost. If the grass is a bit on the thin side grass seed can be added to the mix. The dressing is usually spread over the lawn using the back of a rake or a stiff brush to work some of the mix into the holes. Again it will look worse before it looks better but will soon recover with some rain and grass growth. Whether or not you choose to scarify, aerate and top dress this autumn, September (or October) is a good time for the final lawn feed of the year but it is important to use a special autumn feed and not a summer feed. Summer feeds are high in nitrogen for strong leaf growth whereas autumn feeds are high in potassium and phosphorus which encourage root growth to make the grass more resilient through winter and to be ready for strong growth next spring. Finally any bare patches can be re-seeded using seed mixed with old potting compost. To keep the birds off and the moisture in re-seeded patches can be covered with pieces of clear polythene pegged to the ground which can be removed as soon as new growth is seen. Grass seed sown in September will usually germinate in 7-10 days so it is also a very good time to sow whole new lawns or indeed to lay turf. I won’t go into details on these in this blog as there is plenty of good advice to be found on the internet.

Finally for September I must mention the vegetable patch where the summer produce will still be harvesting well but coming to an end at some stage. Once the ground is cleared there are plenty of crops which can be planted later in the month for harvesting next year. These include winter hardy lettuce such as ‘Winter Density’, garlic, Japanese/Autumn onion sets and Spring Cabbage. On any ground which you don’t plant up rather than leaving the soil bare over the winter when nutrients can get leached out and soil erosion might occur, have a look at sowing a ‘green manure’. We have nearly finished creating another raised vegetable bed and as soon as it is ready we will sow an autumn/winter green manure mix. This will cover the soil through the winter, add some nitrogen as the mix contains some clovers and will be cut down in the spring before the plants can set seed or about a month before sowing the next crops, allowed to wilt on the surface and then be incorporated into the top 6” or so of the soil.

 In the blog for mid-September, as the autumn is such a good planting time, I will take a look at some of my favourite shrubs and the mid-October blog will follow the same theme by looking at some of my favourite trees for gardens. In between at the start of October will be the usual look at the garden for that month and will not surprisingly concentrate on the wonderful colours to be seen at that time.

Until then happy gardening and look after yourselves.

Keith.