A Northumberland Alpine Gardener's Diary
This entry: 22 November 2009 by John Richards
Northumberland Diary. Entry 133.
Two more troughs
As I intimated in my last entry, several troughs required a rework, not just the example described there, so I have tackled two more in the gaps between the gales and the showers, and I thought I would once again discuss the process and show the results.
Yes, we have some wild weather over the last few days, but no more than one expects in late November, unlike our neighbours to the west. What a difference the Pennines make! We are only about 35 miles east of Carlisle here, and some areas within 25 miles of us suffered nearly ten inches of rain (220 mm) in two days. Not as bad as Cockermouth to the south, who received the effects of 370 mm in the same period, but quite bad enough! West of here the Tyne Gap provides a very modest barrier to westerly weather, yet we cannot have received more than 20 mm in the same period. Reason to be profoundly thankful!
The next trough I tackled is the first trough I ever made, or indeed owned. I probably made it in 1972, young, raw and even more foolish than now. It was made out of 'hypertufa', a mix of sieved peat, coarse sand and cement, two parts peat to one part of the other elements. It was made between two cardboard boxes of differing sizes, the kind that you used to get your groceries in then. They (the boxes) were not supported! Wet hypertufa mix is heavy, and the boxes soon became soggy, and then saggy! This was realised too late, by which time the cement had 'gone off''. So my first trough is the shape of a very soggy cardboard box! Much better that the sides of the box had been supported by e.g. bricks, as I have done since. Nevertheless, it is, you will see, very robust, but at least this has allowed it to survive some 37 years! It was very mossy and little had survived except three clones of Saxifraga paniculata, and some rosettes of Sempervivum montanum.
Here it is empty, and in the next picture the lump of tufa (real Welsh tufa) that was found buried in it, with some scraps of the saxifrage adhering.
I decided that the lump was too big to return to that trough, or moved to the others I had plans for. In the end I decided to add it to the end of my artificial tufa mound on the terrace as a sort of annex, with some of the saxifrages in situ. The site I had in mind was overgrown with backgrowth from a huge Parahebe cataractae that waterfalls down the terrace wall, as well as some Cotoneaster congester nana, so I cut them both hard back, freeing up some rooted bits of both for propagation. The new area was topdressed with old trough soil (containing tufa bits) and planted with bits of silver saxifrages. The cutting back is just starting in this photo.
Returning to the trough, as you can see in the previous photo but two there was no problem with the drainage because a large wooden plug had been put in to give a drainage hole when the trough was made. This is covered with crocks, and the trough was filled with a mix of equal parts John Innes 3, coarse sand with some added perlite and some slow-release fertiliser, and top-dressed with the 'alpine grit' from the local garden centre. Unlike the last effort, there was no pretence that this was a tufa trough, so no limestone was involved. Here it is planted.
Apart from rosettes of the saxifrage and semp., everything else planted were this years seedlings. Reading from the left, top row Silene rupestris (seed from Gorge de Verdon), Silene davidii, Dianthus glacialis, second row Primula incana, Androsace carnea, Potentilla alba (also Gorge de Verdon), bottom row Aquilegia nivalis, Androsace bulleyana (own seed), Saxifraga mutata. It may not be immediately obvious that it has been raised onto four small upside-down crock pots, to improve the drainage and air circulation. I have done this with all the replanted troughs.
The other trough tackled is also a curious affair. Only about 200 m up the road from here, a steep wooded roadside bank has low cliffs of shale, so soft that I can easily pick out pieces by hand. The bank hasn't collapsed yet!. About 14 years ago, I took a yorkstone slab and built horizontal shale walls, lightly cementing the layers together.
This trough has never grown plants well, and only four bits had survived to the replant.. On emptying the trough the reason soon became apparent. When I plant a trough, before I ever fill it, I always pour a can of water into the empty trough to check the drainage. This time, none of the water drained at all! The bottom of the trough being a thick slab, there was no vertical drain and I had relied on water seeping out the sides at the base, through gaps that had been left in the shale (this also required the trough to have a slight slant in that direction). These gaps had become very firmly clogged.
By dint of repeated probing with a stiff wire all the densely packed material was freed and water drained readily. The hole was then packed with gravel and shielded with a crock. The trough was filled with water several times to make sure it now drained freely.
Only now was the trough filled (with the same mix as above; I made enough mix for both troughs) and planted. Because I had it mind to top-dress with shards of the shale, I planted the rootballs proud onto a firm soil base (it is always very important to really firm the planting mix in a trough very hard. I use my knuckles, and all my weight to press it in; otherwise the plantings sag in the middle over time. It is also vital to finish with a convex soil profile). Then I filled in with the vertical shards. There was not enough shale and about one third of this top dressing is the commercially available slate. So far they seem to harmonise quite well.
The plantings are as follows (again left to right). Top row: Primula 'Clarence Elliott' (from my own rooted cuttings), Thlaspi sp. ex Pirin (a survivor from the original trough), Primula pulchella; second row Dianthus glacialis, D. subacaulis, D. brevicaulis, Primula gemmifera; bottom row Saxifraga 'Johann Kellerer (another survivor), Minuartia attica (ex MESE), Potentilla alba, Primula involucrata.
Its raining again!