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Wisley's Alpine Diary

This entry: 26 July 2010 by Paul Cumbleton

Log 77

Wisley's Alpine Log

By Paul Cumbleton

2010: Log 77... 26 July

The two summer months of July and August are the most difficult ones for us with regard to putting colour in the Display house. With most alpines having long gone over and the autumn flowerers still a few weeks away, the house lacks the ?wow? factor that we aim to achieve in the rest of the year. However, that does not mean the house is uninteresting. We use a lot of Sempervivums for their leaf colours and many other plants with attractive foliage ? ferns, silver saxifrages, Arisaema, Primula marginata and the like.


Between these we place the few flowering things ? Campanulas, some of the summer-flowering South African bulbs (such as the small Eucomis vandermerwei and Hypoxis species) and the last of the Ponerorchis for example.


With future colour and interest in mind, one of our most recent jobs has been potting on young plants raised from seed. We sow quite a lot of seed each year ? sometimes seed is the only way to get some of the more interesting or rarer items. People often think that we must have access to sources that they don?t whereas in practise we only do what any keen plant people do ? we use the seed exchanges of the AGS, SRGC and NARGS, and scour the lists of seed merchants that anyone can access these days on the Internet. Here are some of the results of this year?s sowings:

From a previous sowing, this year I was pleased to get a Viola congesta to flower. This was the only seedling that germinated:

I am rather fond of the American Ipomopsis and one in flower just now is Ipomopsis aggegata var. attenuata. The buds of this are orangey-red with yellow?

?but surprisingly open to a flower that is white inside with pink spotting:

Most of the genus would be rather too tall for the average rock garden, though there are some exceptions, and the species most commonly grown are best treated as annuals in the UK where they are rarely hardy enough to survive a winter. But they are easily grown from a spring sowing, planted out after the last frosts and then flowering in the summer of the same year for a prolonged period. Their tallness means they are best in a site sheltered from wind as they are easily blown over. I find a better option to counter this is to pinch out the growing tip when they are a few inches high. They then branch and produce several flowering shoots per plant which don?t get quite at tall as the un-branched plants, and if planted fairly close together then help to support each other too.


Outside, we have had a problem with some of our ponds. At the bottom of the rock garden are four large ponds. Normally these have an abundance of plants in them such as this one:

However, two of the ponds now look like this:

The plants have slowly been disappearing over the past 18 months or so. The cause turned out to be fish called grass carp. Apparently some small grass carp were put in these ponds many years ago to eat the more undesirable pond weeds. Now, many years later, they have grown so large that they have been able to eat all the plants in the pond. We aim to catch them and move them to the glasshouse lake. This does not have any ornamental planting but does have pond weeds, so is an ideal solution. We can then replant our ornamental ponds.


There is still some colour on and around the rock garden. This low-growing Oenothera macrocarpa always draws attention with its magnificent large and glowing yellow flowers:

Compare this in close-up to another Oenothera flowring now. This is O. versicolor ?Sunset Boulevard?. This is a taller plant that has smaller but lovely orange flowers which deepen to red as they fade:

Just starting to flower now is Roscoea ?Red Gurkha?, which always seems to be the last Roscoea into bloom:

Also flowering now are the Platycodon grandiflorus ?Astra? series that we grew from seed two or three years ago. These are available in shades of white, pink and blue and are supposed to be a dwarf series. We find however that when planted out (as opposed to being grown in a pot), the blue forms tend to lose their dwarfness, while the white ones stay small ? as you can see:

Finally, alongside the far edge of the main path along the bottom of the rock garden is a bed of mainly herbaceous perennials. Among these are some Agapanthus. There are two in particular that attract attention by our visitors. The first is ?Royal Blue? for its dark shade of blue; the other is ?Windsor Grey?, a rather unusual colour which as its name suggests is greyish:

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