What makes a difference and by how much?

Much of gardening is about making tiny adjustments, improving our soil or conditions, giving our plants a more favourable micro-climate or a longer growing season. Not all the things we can do are going to make the same impact. Obviously in times of drought a good watering will make much more difference to the final result than would adding more fertiliser. But all other things being reasonable then we need to consider how much improvement does one more watering, a dose of fertiliser or say, a thorough hoeing of weeds, make. First of all we need to make the biggest improvements to the performance of our vegetable crops. The soft and tree fruits being perennial can often draw on accumulated resources and so bridge temporary shortages. However most vegetables are short lived and highly developed so somewhat like Olympic athletes asked to perform at the very peak of their ability. Indeed it’s only our weeding, watering and feeding that gives us decent crops from many of them. Of course the season makes more difference than almost anything else. Some years cabbages and spinach thrive and the potato crop is heavy and full of slug holes, other years tomatoes, sweet corn and French beans thrive and the potato crop is light and full of slug holes, well you get my drift. We can offset some difficulties of a poor season say by using cloches in a cold wet one, more water in dry ones and so on. What we cannot improve is the low light of some years, unending heavily overcast dim days give slow growth. Bright ones not only make us happier but make the plants grow well too. Likewise relatively warm nights after cold days (ie the temperature does not vary much because of heavy cloud cover) are a handicap to some such as tomatoes. There are ways to reduce the effect of each season. First; where possible do not grow all the same variety but a selection. Although this increases the effort and cost different varieties are less likely to all respond the same, some do better and some worse. When I trialled outdoor tomatoes it was noticeable with more than thirty varieties that if ten did well, ten were average and ten really good any year. But never quite the same sets of ten the following year. I suggest we tend to grow too many different crops and not enough variety of each. A good plan is to trial each favourite crop for say a three year period. Instead of one or two carrot varieties get a dozen or more. Sow smaller amounts of each simultaneously and keep notes. (If kept resealed, cool and dry the many packets of seed should keep viable for three years of trials- after all you will have plenty of seed to sow thickly.) Any variety that does well for you on your soil over a three year period will be worth continuing with- I cannot believe how well Yellowstone carrots do for me compared to all others. Varieties that only did well one year out of three will have to be damn tasty to be worth perseverance- Pink Brandywine tomatoes spring to mind. Another way to cope with each coming season is to sow in several small batches a few days to a week apart for those usually sown but once or twice anyway. If you sow anything in just three batches you can be sure one lot will do far better than the others. It’s illuminating to watch what happens if you sow a few seeds every day over a month or so- say sow five seeds every day, sometimes all five come up, othertimes barely one makes it. For those crops sown regularly anyway say spring onions, saladings, rocket or radish, then if you can’t sow each day sow weekly or twice weekly. Then regardless of most seasons there will always be one or two batches doing well. For those concerned about all their space being taken up- I know it’s hard but be ruthless. You can sow three rows or pots then dispose of the under-performers, we are not obliged to let every seedling mature…… That brings me on to the next point. Thinning and spacing crops is far more crucial than we tend to imagine. We all understand how weeds compete with our crops- but more of the same competes even harder for exactly the same resources in short supply. Trials showed tomato seedlings germinated together in a pot and pricked out soon after emergence were significantly stronger plants cropping better than those pricked out a week or so later. In a good year crowding does not improve the crops does it, in a bad year it makes it much worse. There is little doubt that early thinning and spacing pays dividends and is something we all could improve! Regardless of the season good weed control can greatly alter the outcome as weeds are such competitors. Weeds take water, nutrients or light so the crop suffers. But worse, some weeds are particularly good at monopolising this or that mineral leaving none available for the crop so really seriously competing. At the same time weeds not within the crop’s root zone are fixing mass which can be hoed in and liberated much as any short term green manure. And a low belt of young weeds well away on either side of a row of seedlings may keep the wind off them much as a full size hedge shields the garden. So it is the close-by weeds that need eliminating more than those further away. Planting out or sowing and then covering with a mulch of weed seed free compost can benefit in all the usual ways but also suppress most weed seedlings appearing nearby. The bare soil between such clean rows or station sowings can then be weeded with a hoe later and less often. Although as stated some weeds are competing for specific minerals it’s their competition for water that is the usual problem. Water is crucial for all plants but vegetables especially so particularly the more succulent ones. Although a covering of weeds does keep the soil surface damp they also waste huge amounts. In most gardens it’s water that’s the limiting factor for plant growth not the other nutrients. Unless you garden in the wettest regions then most weeks of the growing season the rain will not give the inch of fall required by most plants. In the eastern regions potato crops must have extra water nine years out of ten! One good watering when the plants are in flower can near double the yield of potatoes, sweet corn and beans. Regular watering makes saladings and herbs less pungent and lettuces crunchy and sweet. But you know all that. However we tend to forget how important it is to look after our crops when they are smallest. A bunch of little seedlings in late spring do not have very tall tops and neither do they have very deep roots. And yet the top soil can soon dry like a bone if there is sunny windy weather. It is then one prompt watering can save seedlings or at least avoid a check so early on which always reduces the final crop. Water stress may also induce mildews, rusts and other problems. Indeed very close attention to each crop’s water needs is crucial for good results. The converse of water shortage is water-logging. We all know how heavy wet soils need to dry out before the plants can get going and water-logging over-winter does kill many perennials. But it’s unusual for most of us to experience such conditions for long during the middle of the growing season in the open ground. And if such occurrence is common then improving drainage is the obvious solution. Conversely I suspect many of us harm our crops under cover by too early and too frequent over-watering. Our desire to force the pace induces us to water when it is not at all required. Excess water kills by excluding the oxygen the plant roots need but also by poisoning the roots with a build up of dissolved noxious substances. In particular cold wet compost liberates ammonia into the water which rapidly kills roots. So more parsimonious watering of young plants under cover when the growing conditions are poor is critical! Aeration is the opposite of water-logging and I am convinced many benefits of drainage are actually due to the improved aeration. Every effort, including encouraging worms and going over to raised beds, should be made to increase soil aeration, even burying perforated pipes connected to chimneys. As crucially we need to ensure our sowing and potting composts do not pack down or crust. Although it may dilute their fertility it’s worth mixing those with such problems with really sharp sand and using bigger pots. It is well worth buying several brands of potting compost and trialling these against each other for your most important crops. I’ve been staggered by the different performance between them- and my sieved garden compost usually does better (though admittedly much weedier). Feeding itself does of course improve growth, especially with plants in containers with restricted root runs. Conversely I’ve rarely found much real benefit from additional feeding of most crops in the ground. Generally providing the soil with green manures and compost in the rotation feeds most crops sufficiently. (Compost rather than animal manure- either give some instant fertility though compost is better for inoculating the soil with microbes that liberate yet more fertility from the soil minerals.) But to be fair the hungriest feeders such as leeks, brassicas, sweet corn and squashes can respond to extra added fertility applied during their earlier months. Naturally as they also respond to water then dilute liquid feeds are the answer. But although such feeding may help balance some of the more usual nutrient shortages the rarer trace elements may still be in short supply. A fortnightly addition or foliar feed of dilute seaweed solution rectifies any such shortage and makes our crops perform better. And now to come to a conclusion. Which of all these does make the greatest difference? Well the one you didn’t do of course.