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A Northumberland Alpine Gardener's Diary

This entry: 31 August 2008 by John Richards

Northumberland Diary. Entry 89.

D bed renewal

Since I started this diary two years ago, I have not undertaken any major project in the garden. There have been some fairly small-scale developments such as the crevice bed and the tufa bed, and I have started many new troughs and reworked others, but the garden as a whole has stayed intact.

However, I have become increasingly unhappy about one of the 'D' beds, and I promised myself that once the hedges were finished, I would take it apart and start again from scratch. I knew that I had a clear week, and started work last Monday afternoon, since when I have put in several hours hard labour every day, finally finishing this morning (Sunday). As it happened I chose the warmest and dryest week of this wretched summer, but the soil profile was (mostly) moist, and it remained humid, still and cloudy, so the plants came to little harm.

The 'D' beds take a central position in the main garden. They are island beds devoted to shrubs, small trees, and shade and moisture-loving subjects. They are so-called because both have the shape of a capital 'D', the straight side running parallel to the alpine terrace, both being accessed by a 40 m straight path.

One of these beds had got into a very poor state. It suffers badly from being only 8 m at its nearest from an ancient hybrid lime (Tilia x europea) to the south, being partly in its shade, and, more seriously, invaded by its roots. It was first developed 17 years ago, but was renewed in part about 10 years ago, when it became clear that it was overrun with tree roots. This caused me to put a blue plastic liner above the roots, and to fill in with new compost and replant, in the hope that the tree roots could not penetrate above the liner. This photo shows that there was only about 30 cm of compost above the liner.

As can be seen the bed is quite large, about 8 m down the straight side and 7 m deep, perhaps 45 square metres in area. As soon as I started to take it apart it was clear that the plastic liner had not worked, as the bed was full of tree roots again. Presumably these had invaded from the side, above the liner. Equally damaging, the whole bed was infested with two very serious perennial weeds. I believe that both had originated in the root-balls of rhododendrons, but had been tolerated when first detected, a disastrous mistake. One is the rather scarce native oak fern, Gymnocarpium dryopteris (imagine my choleur when this terrible weed was presented on the showbench as an exhibit last season!). The other is a plant I have rarely seen elsewhere, presumably because no-one else is foolish enough to let it anywhere near their gardens. It is an ivy-leaved toadflax, not the one seen commonly on walls, but Cymbalaria hepaticifolia. This appalling pest forms masses of 'spaghetti' under ground, which is at least white and so easily detected, but it fragments in root-balls and is extremely difficult to remove completely. Its strength and persistence can be gauged by this mass of roots which had found its way underneath the liner!

The northern, downhill side of the bed had been raised to the height of three sleepers, partly to give good drainage above the water table, but also to present the bed surface in a more southerly aspect. Consequently, I had six railway sleepers ('ties' in north America) to dispose (of). In the end I left two in place, to hold the new soil in position on the northern side..

Notice two barrows, one for compostable weeds, and one to go into the Local Authority 'green matter' bin. A third container was used for twiggy matter and roots.

Plants were carefully freed from weeds, if necessary divided with a spade until all the weeds within the rootballs could be removed, and placed in the shade under compost bags, and, as it became available, the old liner. These were hosed a couple of times to keep them in good condition.

Once free of plants and weeds, old compost was taken off the liner to parts of the bed already free of liner, and the liner was progressively removed.

When the plants and liner were finally removed, a whole compost bin-full was barrowed in, 14 barrows in all.

Once this had been levelled, five barrow-loads of leaf-mould were added, and then five barrow-loads of old potting soil. The latter added ballast, drainage and nutrient to the rather over-fluffy, highly organic new compost. The next two photos show the finished article before and after the sleepers were put into position. The sleepers provide invaluable access to all parts of the bed, vital when such open compost is used to prevent compaction.

Once the major structural subjects, shrubs, had been returned, the time had come to add herbaceous subjects. Many had been lifted, divided and stored, but I was also able to add about 40 young seedlings of primulas and meconopsis, the latter including M. punicea, gracilipes, speciosa, paniculata, robusta, and wallichii. These had all been raised from seed here, and in total would have probably cost about 150 in the trade, which only goes to show the value of seed-raised plants! Here they are, ready to go in.

The final job was to return the bulbs. This was a much bigger task than expected. For instance, there must have been 300 flowering-size bulbs of colchicums. These were carefully planted round the edge of the new bed, so the foliage would not interfere with more delicate subjects. There were also several hundred erythronium bulbs, and lots of narcissus and snowdrops. Not all the latter have gone back in yet. I was careful to separate out about 100 camassia bulbs, which will be replanted in Sheila's herbaceous border as they are too robust for the new D bed. Here, finally, is a view of the planted bed. No sooner had I finished than it started to rain, and it sounds as if the next week will be wet, so the plants should settle in nicely!

A plant to finish with! Meconopsis aculeata is flowering for the first time. As seen here it is a funny little thing, although I believe there are more robust and blue-flowered forms. In this form, with basal, scapose flowers, it actually keys out as the fabulous M. bella, which only goes to show how misleading botanical keys can be!

John Richards

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