Tomatoes, chillies, sweet peppers, and other such crops, need good fertile conditions to grow well and continue cropping throughout the season. Tomatoes in particular put on a considerable amount of vegetative growth, and produce a large amount of fruit. Providing sustenance is therefore important. Conventional wisdom suggests that feeding should commence as the first flowers appear and continue at, as a minimum, weekly intervals, with a suitably formulated feed, that is, one that is high in potash and relatively lower in nitrogen, to support fruiting rather than encourage growth. Some also advocate the use of a balanced feed prior to fruiting, although I suspect that this is not often necessary.
However, I am rather of the opinion that reliance on liquid feeds is rather unsatisfactory, and where at all possible, feeding of the soil is to be preferred, not least because it removes a burdensome task. It is the time of year, though, that I examine the plants closely to see whether a liquid feed is indeed needed – whilst I prefer not to, I do not allow the plants to suffer unduly through lack of nutrients.
I have grown the typical glasshouse crops such as tomatoes, chillies, peppers, aubergines, and cucumbers, under various conditions; in growbags, pots of differing size and material, and in glasshouse and polytunnel beds. In my view, nothing beats growing in the good, deep, fertile soil of the glasshouse and polytunnel beds. These can be prepared with copious amounts of manure, compost, and natural slow release fertilisers – I use fish, blood and bone – to provide all of the nutrients demanded by heavy cropping plants, without the need for further feeding. Having grown under various conditions, I need no further convincing that the plants are healthier and substantially more vigorous and better cropping when grown in a sufficient volume of fertile soil than when grown in small pots or growbags that quickly become impoverished and are then maintained only with a regular application of liquid feed.
It is not always possible to grow in beds, and there is the possible disadvantage that, from time to time, one might need to change the soil, although it should be good for at least several years when well maintained. Not all glasshouses offer beds, and one must then look to such things as growbags and pots. I have found the former to be rather disappointing. In my opinion, they do not offer sufficient volume of soil, dry out quickly, and are then rather difficult to wet. Neither am I satisfied with the contents of the typical growing media, even though specifically formulated for these crops. Volume of soil is problematic, but it is perhaps the challenge of keeping the compost suitably moist that is of most concern; an automatic watering system would certainly be advantageous. Some growers get around some of these problems by stacking two growbags together, making large cutouts between them, or by inserting pots with their bottoms cut out, to provide both additional soil and easier watering.
There is also the so-called ring culture. Originally, this involved placing a ring, which was filled with compost, on a gravel bed. Feeder roots would develop in the compost, whilst deeper roots would seek out water below. This has been replicated in modern times with plastic pots with two concentric rings designed to be inserted into growbags. Feed can then be applied to the feeder roots within the inner ring, and water around the outside, perhaps helping to prevent the feed from being washed out. I must admit that I have not tried such methods, and indeed have no doubt they are an improvement on the conventional growbag as they at least increase slightly the volume of soil, but I remain unconvinced concerning their utility, and would prefer a large pot instead.
Pots, on the other hand, do offer some prospects of preparing a good basis for glasshouse crops, if they are of sufficient size. Growing in small pots has the same problems as growbags; insufficient volume of soil, and hence the necessity of feeding, and a need for frequent watering. Within reason, the larger the pot the better; I have found 10 litre pots to be ideal for chillies, but would not want to use less. We currently have 44 chilli plants in the ‘chilli house’ – our small glasshouse, which, after the spring propagation rush is over, is dedicated to chillies for the remainder of the season – each planted in a 10 litre pot.
In addition to pot size, the provision of a suitable growing medium is of great importance. Organic multipurpose or vegetable growing composts are not entirely satisfactory, in my view, lacking substance and nutrients. I will not use a non-organic compost, not so much because of any peat content that may be present in some offerings – which, in my view, could be sustainably harvested, although this may not be the case at present – but because of the synthetic feeds, which I consider to be both undesirable and unnecessary. The organic composts, though, tend to be rather woody and coarse in nature. They vary, with some being markedly better than others; I have had good results with Vital Earth and New Horizon brands. In my experience, the former offers a reasonably fine texture, whilst the latter, which is more readily available from garden centres in my locale, varies depending on the specific blend as several alternative products are available.
Perhaps other growers would disagree, but, personally, I do not like to use these composts as they stand. I prepare, instead, a mixture of, very approximately, at least one part manure, with one part soil – either new top soil or old potting soil – to 2 or 3 parts organic multipurpose. Sometimes I will substitute some homemade compost for some of the multipurpose, depending on how much I have to hand. I add a sprinkling of fish, blood and bone as a slow release fertiliser. In the past, I have used this mix for growing all manner of glasshouse crops, with good results. I now use this mix, or something similar, for potting on of tomatoes, peppers and chillies, as, to my mind, the multipurpose compost is simply not sufficiently rich to support sustained growth, and for growing chillies in their 10 litre pots. Generally, there is sufficient nutrient to provide for an entire season’s growth and fruiting without feeding, although I keep an eye on things towards the end of the season and feed if there are clear signs of any lack. I find this approach to be rather more convenient and, to my way of thinking, entirely preferable to a regime of regular liquid feeding.
When we first began construction of the kitchen garden, I rather imagined using more liquid feeds than has so far turned out, but in any event cannot see any reason to use anything other than natural, organic feeds. I consider synthetic fertilisers to be, ultimately, more harmful than helpful. Manures, compost, natural slow release fertilisers, and feeds made from natural ingredients are all that is needed to supply the necessary nutrients. Traditionally, liquid feeds were often made by steeping a sack of manure in a tank of water. The resultant brew was applied, diluted as appropriate, to various crops, but especially green crops such as celery. I am rather disinclined to use manure this way, preferring instead to apply to the ground, where it is processed properly, rather than applying to vegetative growth that will eventually be eaten. Common homemade feeds today are produced by steeping, for example, nettles, for nitrogen loving plants, and comfrey, which is high in potash, for fruiting plants. Concentrated organic feeds are also widely available, and in appropriate formulations for crops such as tomatoes and peppers, so there is no need to use anything unnatural. I do, from time to time, process perennial weeds and others that I would not add to the compost heap, by storing in black bins, covered in water, for some months. It is a rather smelly process, but when the material is sufficiently broken down, I add the partially decomposed remains to the compost heap, and can then use the liquid, diluted with several parts water, as a feed. This has been applied to good effect on, for example, runner and French beans.
All of these feeds can be useful, especially if the plants are seen to be struggling. I just find it more convenient, and consider it otherwise preferable, to feed the soil first. Application of liquid feed, if it becomes necessary, is rather a sign of inadequate soil preparation and something to be addressed over the winter and early spring. Of course, if growing in containers of insufficient size, feeding will be unavoidable. This year, despite a slow start during the cold spring, the chilli house has made great growth, and looks to be preparing for a good harvest. I have not yet fed the plants, and I doubt now that they will need any further feed, nor do I see any inadequacy in the growth or cropping of the plants. The tomatoes, in their beds, are also in fair condition, as displayed in the recent post describing the tomato taste test, and, again, I do not perceive any need for further feeding.