Companions... and a cold

Unfortunately illness (and a very cold spell) has kept me away from the allotment this week and it stands neglected (I expect the weeds are creeping across that lovely newly-prepared soil as I type). The weekend looms and I have vowed, even if I can't face the hard work of digging, to start sowing some seeds.
My seeds have been arriving all week and sit jumbled in a box under the kitchen sink. I really did order quite a lot... I think the only thing that hasn't arrived yet (not including plants which will come later in the season) is my seed potatoes, which is annoying as they really need to get started soon (not that there's weed-free space for them just yet I suppose!). They could do with a bit of organising and planning before I start planting anything so I will try to do that today, in between nose-blowing and drugging myself up on paracetamol and sudafed...

In the meantime I thought I'd tell you about the other plants I intend to grow around the place to benefit the real crops.
Companion (or combination) planting works on a few different principles. There are plants which attract pollinating insects (bees, hoverflies, butterflies) or insects which prey on pests (ladybirds, lacewings, hoverflies, parasitic wasps), there are plants which distract pests from the important crops (rather the marigolds get eaten than your precious lettuces), and there are plants which actually put pests off (coriander repels aphids, for example). There are also plants which affect the soil in ways which benefit other plants (carrot roots exude a chemical which helps the growth of peas), and finally, crops which are grown together simply because it's more efficient to do so (like growing radishes with parsnips; they mark the row during the parsnips' long germination period and are ready to harvest before the parsnips need the space).
There are hundreds of good (and bad) combinations, but I only have a small plot so I have tried to choose just a small selection of herbs and flowers that will bring the greatest benefit to my crops. And here they are:
Comfrey not only improves the soil in which it grows, but makes excellent compost and liquid fertiliser. Its incredibly deep roots bring up nutrients from the subsoil which wouldn't otherwise be available to the plot. All that goodness is transferred to the leaves, which contain 2-3 times more potassium than farmyard manure as well as lots of calcium and phosphorous, and can be cut four or five times a year for composting, mulching or fertiliser. Apparently slugs and snails love it too so it may help to lure them away from other crops.
Lavender attracts bees, butterflies and hoverflies but puts off many flies, fleas and moths, and is said to benefit the soil with its antiseptic properties. Many Victorian gardens were bordered with lavender for these reasons.
Tansy concentrates potassium in the soil and attracts ladybirds to the area, but repels lots of nasties like cabbage worms, squash bugs, borers, ants, flies and moths. It is also good to compost, like comfrey.
Yarrow is another good all-rounder, attracting good insects like ladybirds but deterring almost everything else. It is very hardy and doesn't mind being walked on, so I'm thinking of growing it on my paths.
Creeping Thyme may be another good one for paths; its flowers attract lots of pollinating insects and its strong scent deters cabbage worms.
Rosemary deters cabbage butterflies, bean beetles and carrot flies. Slugs and snails won't touch it, but this may only protect plants if used as a border.
Sage also protects against cabbage and carrot pests. Although cucumbers apparently have a particular loathing for it, which might make me reconsider.
Mint repels ants and aphids, cabbage worms and black flea beetles. It is also supposed to improve the health and flavour of cabbages and tomatoes when grown nearby.
Hyssop is a favourite of bees, and protects against cabbage butterflies. I'm not sure if it repels them or acts as a sacrificial plant and just distracts them, but they did such damage in my garden last year that anything is worth a try to avoid the dreaded cabbage caterpillars!
Bee balm, as the name suggests, attracts bees. It's also said to improve the growth and flavour of tomatoes and it's beautiful!
Wormwood is one I haven't quite made up my mind about yet. It's supposed to be repellent to slugs and snails, but some things I've read have suggested negative effects too, like suppressing the growth of other plants nearby. Maybe I could grow it away from other plants and just use cut pieces as a repellent. I'll have to think about it some more...
Horseradish has a beneficial effect on potatoes and fruit trees, and repels eelworms. It can also be made into an effective insect spray, I'm told...

All the above are perennials, some of them known to be invasive and even considered weeds. For this reason I'll have to keep a close check on them to prevent them taking over the plot (or anyone else's!), and maybe take steps to contain the roots in bottomless pots or similar. These perennials will be grown in permanent borders and pathways.
The plants that follow now are annuals and can be planted in different places each year, with the crops they are expected to benefit the most.

Radishes protect squashes from borers and beetles, so I'll grow them even though I don't like to eat them, and magazines seem to always be giving away free radish seeds so I'd better do something with them!
Sunflowers attract pollinating insects (hopefully from miles around!) and are something I'd really like to grow anyway, not least for the seeds and the stems, which are useful dried and kept for bean supports etc. next year.
Marigolds are good to grow with anything; they deter all kinds of pests and distract the ones they don't put off altogether, they attract pollinators to the area, they suppress harmful nematodes in the soil, they aid tomato growth and they're even edible!
Nasturtiums have similar effects, particularly deterring aphids and squash bugs and providing a tasty alternative to lettuce for the slugs and snails. Like Marigolds too, they are edible; the leaves are apparently great in sandwiches and the seeds provide a good home-grown alternative to black pepper!
Celery is not something I'd grow to eat, but it deters those pesky cabbage butterflies so it's in with my brassicas and I'll give the crop away!
Coriander puts aphids and spider mites off, so I'll plant it near squashes, beans and lettuces, which all suffered in the garden last year.
Basil is said to aid tomatoes, and vice versa, and also deters aphids.
Borage is apparently the best plant for attracting bees, and deters tomato horn worm and japanese beetles. It aids strawberries and is good for the compost heap. It's also supposed to be a pleasant culinary herb which I may experiment with...
Parsley attracts hoverflies and parasitic wasps, deters asparagus beetles, and encourages tomatoes and asparagus.
Petunias also deter asparagus beetle, tomato pests and many more, and can be made into an insect spray.

Wow, that was a lot of information in one go! Of course, all these combinations of plants are recommended by the experiences of others only and may not work in every environment; I suspect this is the beginning of a long learning process before I get it right. But bring on experimentation!

For more about companion planting, follow these links:
Golden Harvest Organics
Down Garden Services
Self Sufficient'ish'
(All these sites have plenty more useful information too; have a look around.)