May 2023

April was cold and wet here at Longmeadow and pretty miserable for gardeners right across the UK. However, the garden seems not have minded too much and it arrives at May luminously green and full of flowers with more appearing every day.

The truth is that the is an almost irrepressible urge to grow, and the growing light - which is so noticeable at this time of year, whatever the weather - is just as important as the temperature. Also the rain, however unpleasant for gardeners, is a blessed relief after the extreme drought of last year.

In Britain May is the often the most beautiful month because not only does the whole natural world burgeon and blossom but there is a thrilling sense of hope and expansion like a slow and beautiful explosion of life.

In practical terms the soil is warming up and so anything planted in May will grow quickly and well. However in colder areas care should be taken to protect tender plants from late frosts. These rarely kill plants but they can and do nip off tender new growth and hold up future flowering.

Although I will plant out my tender plants such as cannas, dahlias and bananas this May for perhaps the last time. I have decided that it is too costly and too wasteful of carbon-releasing energy to protect them from the increasingly extreme cold (and drought) that climate change is bringing. This means that I will leave them in situ over next winter. I am beginning to plan and plant hardier replacements, particularly in the Jewel garden, to make the garden more adaptable, resilient and in tune with the changing climate.

I will, of course, keep these pages posted on how we get on.

May Jobs

Planting Tender Annuals

By the middle of May  tender annuals like sunflowers, Zinnias, Cosmos or Tobacco plants can be planted out into all but the coldest gardens, especially if you have hardened them off for at least a week. Hardening off is important and will means much faster growing and longer-lasting flowers - so if you buy any of these annuals from a garden centre over the coming weeks, do not plant them out immediately but put them in a sheltered place for a week to acclimatise to your garden, as they will probably have been kept sheltered for best retail display. 

I like to use tender annuals both in containers and borders and in the latter I do not use them as bedding but to enrich the general tapestry of the overall planting. So I place them in groups so they make drifts and clumps rather than straight lines. 

Space them about 12 - 18 inches apart in a sunny situation that is sheltered from strong winds and water them in well. As long as the temperature does not drop below 5 degrees they should grow strongly and flower well into autumn. 

Bring Out Citrus Plants

My citrus plants spent the winter in the new greenhouse but at the beginning of May I bring them outside although I still keep some fleece to hand to cover them if the temperature plummets. 

This is also a good time to prune them, cutting back and damaged, straggly or untidy branches. Oranges and lemons are very forgiving of hard pruning and need reinvigorating so I look to removed a few of the oldest stems every year that can be replaced by new growth.

The Chelsea Chop

The Chelsea Chop (so called because it is done any time in the weeks around Chelsea Flower Show which has traditionally, in pre-covid days, been in the 3rd week of May) is a way of extending the flowering season of late-flowering herbaceous perennials such as heleniums, sedums, lysimachia or solidago (Golden Rod). If you have several clumps of these plants then cut one of them about half way up the existing growth. If you have just one big clump then reduce just one third of the plant in this way. The result will be that the pruned section will produce side shoots bearing extra flowers which will bloom a few weeks later than the uncut growth and extend the display into autumn.

Cut Back Allium Leaves

Unlike most bulbs, the foliage of alliums can be cut back immediately after flowering. In a border this will create space for planting tender annuals such as cosmos, zinnias, tithonia or sunflowers. 

Lily Beetle

Check the leaves of lilies and fritillaries for lily beetle.These have a bright red casing on their upper side but are brown on the underside so although very visible when nibbling the leaves - which they do voraciously - they will drop off if they sense trouble and lie on their backs on the ground so are completely camouflaged. There is no known predator so the only control is to pick them off by hand and dispose of them.

Divide and Move Grasses

Unlike herbaceous perennials, grasses are best divided once they have started to grow vigorously. Lift the clump and divide into fairly substantial sections - they grow slowly so do not cut them up into too small pieces.  Replant them at the same level they were in before and water in well. Keep watering them weekly until they are growing strongly. 

Some grasses seed themselves freely and form crowded clumps and these can be thinned and moved by lifting entire young plants and repositioning with more space around them. 

Stake and Support Herbaceous Perennials

Any plant that has been knocked or collapsed never looks the same, however carefully you prop it up so the secret is to  support plants before they need supporting . If you place supports in position whilst the plants are still relatively short they will quickly be hidden by the new growth and as a result your borders will not look corseted and constrained. It does not matter what you use - I prefer home made metal supports that are rusted and almost invisible after a day or two but stakes and twine or twiggy prunings all work well.

Divide Aquatic Plants

By the middle of May the water of any pond is likely to be warm enough to plant into and to lift and divide any existing plants as well as plant deep water aquatics like water lilies.

Deadhead Tulips

If you have tulips growing in borders, deadhead them once they are past their best. This will stop the development of seed so that all the energy goes into forming new bulbs for next year’s flowers. The best way to deadhead them is simply to snap off the spent flower with the growing seed pod using your fingers.

Do not cut back the stem or any of the foliage as this will all contribute to the growing bulbs as they slowly die back. 

Tomatoes

It is time to plant out tomatoes in a greenhouse- although wait till the end of the month for outdoor ones. This is because tomatoes hate too much temperature fluctuation and May nights can be chilly- especially if the days are warm. Plant them deeply, burying them right up to the bottom leaf as the buried section of stem will develop extra roots. 

As the young plants grow they form shoots between the leaves and the stem and these are known as side-shoots. They grow with extra vigour and although they do bear trusses of fruit, they take energy from the plant and reduce the overall harvest as well as making a cordon plant straggly. So they should be removed as they appear. 

The best way to do this is in the morning when the plant is turgid, simply breaking them off with finger and thumb. However in the evening they will be limper and may tear the plant so should be cut off with a knife.

Sow French Beans

If your soil has warmed up - and only feeling it with your skin will determine that -  then you can safely sow a batch of French beans, both dwarf and climbing. These are tender plants that will be knocked right back by a touch of frost and will survive but not grow if the temperature drop below about 10 degrees and then become fair game for slugs and snails.  But by the time they have germinated we will be clear of those cold temperatures in most areas and the young plants can grow strongly. 

Sow dwarf beans in rows in well manured soil a with each bean spaced 6 inches apart and the rows 12-18 inches apart.  For climbing beans sow two seeds at the base of each support and removed the weaker of the two once one is established and growing strongly.  Water them well and keep them watered throughout the growing season.

Prune Early Flowering Clematis

The best time to prune early-flowering clematis such as c. montana, armandii, alpina and macropetala, is immediately after they finish flowering. Obviously the timing of this will vary considerably in different parts of the country but the principal remains constant and for many of us this occurs at the end of May. 

Next year’s flowers are formed on all the new growth made from this period until late summer so if you prune them much later than mid to late June you will be removing potential flowers that would bloom next spring.

Pruning of these clematis is solely to maintain their size and spread for your convenience rather than for any horticultural benefit. So cut back freely, not worrying about individual stems or the position of the cut. Then when you have finished, weed round the plant, water it well and mulch generously with garden compost or bark chippings.

Make Compost

Compost is the alchemy of a garden, turning waste into black gold and we should compost every scrap of garden and kitchen waste. The secret of making it reasonable quickly is to have a good mix of matter high in nitrogen (green) like grass clippings and drier material (brown) that is high in carbon and then to aerate it often by turning it. This does not have to be a major operation- just forking through it will help a lot. The point is to get oxygen into the heap which in turn feeds the bacteria that eat the decomposing material and convert it into compost which will then enrich your soil with essential bacteria, fungi and nutrients better than any product known to man.

Sow Biennials 

Now is the time to sow wallflowers, honesty, foxgloves, forget-me-nots or sweet rocket for a lovely display next spring and summer.  Biennials differ from annuals, which grow, flower and set seed all in one growing season, in that they grow fast from seed and develop strong roots and foliage in one season and then flower in the next. 

For most this means that they germinate and grow without flowering in summer and autumn, remaining dormant over winter, then have another burst of growth before flowering in Spring and early summer. 

The great advantage of biennials in our borders over annuals is that they are hardy enough to withstand a cold winter and quickly produce flowers in spring without having to wait for the plant to grow first. 

Sow the seed thinly in a seed tray, cover them with vermiculite and put to one side to germinate. They do not need heat but a sheltered spot or porch will help. When the seedlings are large enough to handle prick them out into pots or plugs and grow them on so the young plants are ready to plant out in early autumn where you want them to flower next May.

Divide and Move Primroses

The best time to plant or move primroses is after they have finished flowering but whilst their leaves are still fresh and growing strongly. Lift a clump and gently pull them apart to make a number of smaller sections. These can then be planted to either spread the existing group or ion new locations. Water them in well. They should continue growing but when the leaves start to fade and look shabby cut them back hard. New, fresh leaves will soon appear to replace them.

Marsha Arnold 

Marsha Arnold, whose photographs feature not only on this website but also in many of my books, has new dates available for her fantastic photography workshops. For more information please visit https://www.marshaarnold.co.uk/workshops-overview