Hi Bruce
Isn't Cahors lovely? Shame you don't much care for wine, because some of the local wines there are fabulous (and highly sought after) Château du Cèdre, for example, is pretty much impossible to buy without visiting them in person. And you could almost make money on buying there and bringing back to the UK...
The vines' budburst happens in early spring and then the flowering, closely followed by fruit-set, occurs some 40 - 80 days later depending on the place and the weather (a sharp frost is an absolute disaster at either of these critical times. In Bordeaux, for example, where cold weather remains a risk, they throw a party after a frost-free flowering).
I'm perfectly sure that by now, 27 May, it will all have happened in Cahors, and was probably doing so when you were there. Malbec is the local variety (now as, or even more, famous, from Argentina) has a notably poor fruit-set, which means subsequent work in the vineyard and summer pruning (or else less good wine due to the inclusion of under-ripe fruit).
There are literally hundreds of ways of training a vine, and no one of them is exclusively used in Cahors. It will be a mixture of bush-vines (called 'Gobelet' in French - as it sounds, close to the ground, difficult to work, limited yields of concentrated fruit) and a Cordon system (called 'Guyot' and more likely - more easy to work, more controllable). This year's cane will support this year's buds/shoots/bunches. After the harvest they will prune, a new cane for next year, and a new bud for the following year's cane. The most helpful explanation of this system is that in Spain it is often called 'Vara y pulgar' "finger and thumb" and it alternates annually. This year the grapes grow on the finger. Next year they will grown on the finger that sprouts from where this year's thumb is/was and so on.
Wine students can take several lectures, and a vineyard visit, to fully get to grips with this, so I hope I have got it across without being dull.
What then grows is the leaves that actually cause the photosynthesis that gives the plant its sugars and enables it to ripen the fruit. These will also be useful for shade later on (it can get ferociously hot in Cahors in the Summer, as you may have guessed). In some cooler places the leaves will be plucked or trained away from the bunches to maximise sunshine, in others deliberately allowed to grow to provide shade.
A vineyard can be harvested mechanically, and lots of big ones are. I doubt this goes on in Cahors because of its history and topography, and possibly the Appellation rules may forbid it.
Mechanical harvesting has the advantage of being quick (and vineyards can ripen quicker than even large teams of pickers can harvest), and it can be done in the middle of the night (much better to pick cool grapes to avoid subsequent spoilage and/or the need for chemicals). The machines harvest by shaking the trunk, so that the ripe berries fall off, but (theoretically) nothing else does. But the plants need to be specifically planted at the right spacing, on relatively flat land, and trained, to suit the harvesting machines. The machines are incredibly expensive, and obviously only really used once per year (in fact they are so pricey that after the northern hemisphere harvest they will often be dismantled, disinfected, and shipped to the southern hemisphere for the harvest there, and then back again). A manual harvest has the advantage that people can be selective and collect only the grapes that they are instructed to - eliminating the diseased, insect-bitten, bird-pecked, under or over ripe etc. Machine picked grapes will either need to be sorted through at the winery, or else everything goes into the ferment: spiders, twigs, leaves, mud'n'all (the Aussies call this MOG [material other than grapes]), cheaper, but the wine will be less, er, sophisticated.
Vines will carry on fruiting almost indefinitely (no one is actually completely sure whether vines ever die of 'old age'. The Great Vine at Hampton Court is still going 600 years after Henry VIII planted it, although it is very well looked after. There are other similarly venerable vines in the Holy Land and Greece). But the older a vine is, the less fruit it yields. The less fruit, the more concentrated the flavours, but it may cease to be economically viable compared to harvesting lots more fruit from the amount of land you have and making more - albeit it less good - wine. Traditionally the French used to routinely replant after 40 years, but after the evidence of Australia (some friends of mine have the oldest commercial vineyard in Australia planted in 1843), many French producers are leaving vines in the ground for much longer - there seems to be a sort-of plateau of low yield that the vine descends to and then stops decreasing.
The term "Vieilles Vignes" on a French label guarantees you precisely nothing "I'm just off to plant a vineyard of vieilles vignes" runs the vigneron joke, but there is a move to make this term mean legally a vineyard of over 25 years (which still isn't really very old) but it hasn't happened yet.
In the 1850s a louse - phylloxera vastatrix - was introduced to Europe from North America. It then ravaged all the vineyards of Europe and destroyed them. The European vine had no resistance to it (the native American vines do have resistance to it, but unfortunately the wine made from their grapes tastes horrible - kind of animal and fox-musky - if you have ever consumed Welch's Grape Juice in the USA, you can get a sense of it, but it is only really fermentation that brings out its true awfulness). To cut a very long story short, the only solution to this problem (and they tried a LOT of other things before anyone came up with the solution) is to plant an American vine in the nursery or vineyard, wait for it to establish a root system, and then cut off the top and graft in a scion of the desired European vine. The two species are close enough that this works (rather as you can graft the branch of apple onto a pear tree and it will grow, and continue to produce apples). But the resulting plant will always have the graft point as its weak part, and some ailment will usually take hold after the plant grows older. Phylloxera has never been in some places. Until recently Australia was one of them, although it's now arrived, and so it is not a matter of whether these old vineyards on their own roots will die, but when.
A neat vineyard - and they do take immense pride in them - is probably a sign of wine made with great dedication, and therefore a good indication, but it is not in itself an arbiter of quality.
Cahors used to be called "The Black Wine of Cahors" and they had a reputation for being fearsomely tannic, brooding monsters of wines which required either lots of time in a cellar or a plateful of wild boar.
These days, the producers (some even taking a leaf or two from Argentina's book) are making less intense and more elegant wines, often including some Merlot in the blend, or more judicious harvesting. The wines can be very good value for money compared to other similar wines from South West France, especially the Bordeaux-alikes. Still nice with wild boar though!
Sorry, I appear to have over-answered your question.
Cheers
