Plant of the Month: October

Allium cernuum – to buy or not to buy? That is the question.

by Sue Gray

I expect that, over the years, all of us have bought, or been given, plants that we have later regretted.  In my case the regret is usually associated with the performance of the plant, and how keen it is on world domination!  I think I am fortunate in having good loamy soil; I can claim no credit for this – it is what I inherited, which is as well as I am very bad at preparing soil for planting.  If there were an Olympic games for plants, I could nominate several plants for inclusion in a sprint relay, Silene fimbriata, Adenophora, Centaurea and some Phlox to name but a few, but in the main these can be controlled (with the exception of Japanese anemones!) by judicious digging out or, as a last resort, spraying with weed killer, but the ‘self-seeders’ are a totally different matter.

Allium cernuum

The plant that has been causing me particular anguish in recent years is Allium cernuum.  I know it is very attractive but it has got everywhere since I acquired it at a garden on one of our Group holidays some years ago.  I had decided that I would try and use as many bulbous plants as possible in one particular bed and, as they were so pretty, I think I might have even bought two pots.  First mistake.  I should have been ‘put on enquiry’ (as we used to say in my former working life as a bank clerk) by the fact that the garden owners had so many pots of it for sale; it has taught me ever since to be extremely wary of any amateur gardener with a lot of one particular plant for sale!  I brought them home, planted them, and over the years they have cropped up throughout the bed and in the gaps between the paving surrounding the bed.  Of course, they are no respecter of space and quite likely to appear in the middle of other established plants, as they have done in some clumps of, what I believe to be, Allium senescens.

Allium senescens

These alliums are much better behaved; they do not seed around but form clumps of semi-evergreen foliage about 25cms tall with slightly taller mauve flowerheads in mid/late summer.  As they bulk up so well, over the years I have split them and formed four good sized clumps, two in the front garden and two in the back, all of which had A. cernuum growing up through them.

I decided that the time had come to deal with the interlopers, but realised that to do so I was going to have lift all the clumps and try and identify which bulbs belonged to which allium.  As a first step, when the flowers of A. cernuum appeared, I cut the head off, thus hoping to prevent further seeding around, but leaving the stem which I should be able to trace back to the offending bulb.

A. cernuum on the left, one of the lifted clumps on the right

This actually proved to be easier than I could have dreamt, for when I lifted the clumps I discovered that A. senescens – if that is what they are – as opposed to A. cernuum, actually do not remain as individual bulbs, but join together, forming woody, root-like, structures below the bulb.  The clumps were so tight knit that they took some prising apart, but I hope I have managed to remove all the offending A. cernuum bulbs, many of which had already started sprouting in readiness for next year.  This image shows the individual bulbs of A. cernuum on the left and a section of one of the lifted clumps on the right.

An added bonus of this operation is that I was able to identify, and remove, a number of triteleia which, in my book, fall in to the same category as A. cernuum!

My only problem, now, is that as they were such good clumps, and I have only replanted a small portion of each, I have about 20 pots available for sale.  So, if you see me with them, please ignore my comments about amateur gardeners with lots of the same plants for sale, and relieve me of some.  I promise that they are very well behaved, and lovely additions to the mid/late summer border.

Plant of the Month: September


by Kate van Heel

Throughout history the hydrangea has been especially significant in Japan, where many believe the flower originated. According to a Japanese legend, the hydrangea became associated with heartfelt emotion, gratitude for understanding, and apology after a Japanese emperor gave them to the family of the girl he loved to make up for neglecting her in favour of business and show how much he cared about her. Pink hydrangeas are especially associated with genuine emotion because their shape resembles a beating heart.

The genus Hydrangea contains about 75 species of shrubs, trees and woody vines, along with hundreds of named cultivars. Hydrangeas are grown primarily for their large flower clusters that vary in shape from flat lacecaps, to long panicles, and large, round mopheads. 

The colour of hydrangeas, except for white hydrangeas, depends on the acidity of the soil. You can make pink hydrangeas turn blue by increasing the acidity of your soil. Apparently you can increase the acidity by adding coffee grounds, citrus peels, and crushed egg shells, although I have never tried it.

One of the most popular hydrangeas is Hydrangea arborescens ‘Annabelle’ .

Hydrangea arborescens ‘Annabelle’

Hydrangea arborescens is a large bushy North American shrub bearing a mixture of tiny fertile florets and larger more showy sterile ones, which in fact have coloured bracts in place of petals. Hydrangea arborescens ‘Annabelle’ has only sterile florets, which makes the flower heads much larger, like spectacular white balls up to 30cm across. The Royal Horticultural Society has given it an Award of Garden Merit (AGM). However, its only failing, I think, is that the flower heads are so heavy that after a downpour the whole shrub flops over and never really recovers its former glory. I have tried both cutting the shrub back very hard in Spring to 30cm, and also pruning less severely but to no avail. However, Sarah Raven recommends Hydrangea ‘Incrediball’, a new variety of Annabelle type Hydrangea from the USA, that boasts giant flowers on very strong stems. It apparently produces strong, sturdy stems which support giant, football-sized blooms – hence the name ‘Incrediball’. They are meant to be tolerant of all the wind and rain that a British summer can throw at them, so perhaps it is a better option.

Another of my favourites is Hydrangea paniculata ‘Limelight’. It opens a  bright acid-green then the flowers fully flatten and turn pure ivory, before being washed with rich pink.

Hydrangea paniculata ‘Limelight’

It likes a cool, semi shaded part of the garden where its flowers will stand out and doesn’t flop after rain. Although the only essential work is to remove dead wood in spring, it will flower more prolifically when pruned back annually to a framework of branches. Each spring, cut back last year’s stems to a pair of healthy buds to maintain a permanent framework.

My third choice is Hydrangea aspera. H. aspera is an erect deciduous shrub to 3m tall, with softly hairy, lance-shaped leaves to 25cm long and flat flowering heads with purple fertile flowers and showy white, pink or purple outer sterile flowers in late summer, which are attractive to bees and butterflies. Like Hydrangea quercifolia, this needs only minimal pruning in spring to remove dead and over-long stems. A new addition to my garden is Hydrangea aspera ‘Hot Chocolate’. The underside of the leaf is striking burgundy, whilst the top is chocolate brown, fading to deep green later in the season. The flower colour is pale peach/pink which contrasts well with the leaves. This is planned to replace a pink Annabelle which has decided to flop unacceptably.

These are my three choices but there are so many beautiful hydrangeas to choose from.  Most hydrangeas will remain in flower well into September, so there is a generous selection of stunning varieties to choose from. Also the final flowerheads of the year can be left on the plant to provide winter interest.

Hydrangea aspera Villosa Group


Hydrangea arborescens ‘Annabelle’ and H. aspera Villosa Group by permission of HPS Image Library

Hydrangea paniculata ‘Limelight’ copyright Kate van Heel