Thanks for all your replies and advice, particularly Bamboo for a straightforward answer relevant to the question.

Composted leaves, grass clippings, kitchen scraps, worm castings, horse/cow manure, wood ash, grounded egg shells, wood chips, used coffee grounds, fish or bone meal all provide a very rich, steady, well balanced fertilizer that will feed the microbes over a long duration. It contains all the plant foods and trace elements essential for vigorous growth, abundant flowering and ripening of fruit.Often those synthetic fertilizers will cause an unnatural growth spurt (like taking hormones) but will flop over because of undeveloped root system. The organic matter breaks down in the soil into a sticky substance containing humic acids or humates which hold the soil particles together loosely and trap moisture and nutrients. For roses Vitax Q4 should be mixed with the soil prior to planting and then used as an annual dressing every Spring. Potash also helps to harden growth, potentially making foliage more resistant to disease and weather. The instructions on Growmore and Vitax Q4, for example, say feed in early March then again 6-8 weeks later but you say this may result in a toxic build up.

Nitrogen- and phosphate-based synthetic fertilizers leach into groundwater and increase its toxicity, causing water pollution. What I usually do is broadcast growmore in the latter half of March or early April, turning it in lightly to provide a readily available 'fix' for the plants, then apply composted materials as a mulch over the top - no need to dig it in (though you can if you prefer) it gets taken down into the soil anyway over time, to take care of longer term plant and soil health. Chemical fertilizers tend to leach, or filter away from the plants, requiring additional applications. Synthetic fertilizers kill beneficial microorganisms in the soil that convert dead human and plant remains into nutrient-rich organic matter.

Even if you use Vitax Q4 as a general slow release fertiliser at the beginning of the season the Vitax Premium liquids range will really help to give your plants a boost. Q4 Pelleted Fertiliser should be applied to the growing media before sowing and planting flowers and vegetables. These fungi develop into a mycelium which forms an association with the plant’s roots increasing the roots’ ability to absorb water and nutrients, so aiding establishment. For tomatoes and chrysanthemums, it should be applied prior to planting and then used as a regular feed at 3 to 4 weekly intervals throughout the season.

Originally developed for professional growers, Vitax Q4 fertiliser has proved to be an outstanding general purpose fertiliser for use on a whole range of crops, including fruit, vegetables, flowers and roses. They contain seaweed to stimulate plant growth; seaweed is also reputed to make plants more resistant to stress from lack of water.However, if Richierich wants to feed specific plants, and he/she does, then the answer is as Bamboo has given. Over use or over application seems to be a common problem in the States, much more so than here - I've observed this from my long standing membership of an active USA based gardening site. If you're a follower of 'no dig' gardening, then broadcast the growmore and apply a mulch over the top, without digging the soil, provided there's no weed/moss growth present. Originally developed for the commercial grower, Q4 Fertiliser is the trusted choice for producing bigger, brighter blooms and bumper crops. Soils rich in organic matter re also better at hanging on to nutrients and supplying them to plants’ roots.

Blood meal, fish emulsion, seaweed are excellent sources of supplemental fertilizer if there is some obvious deficiency. Vitax Q4 contains the vital plant foods and trace elements essential for vigorous plant growth, abundant flowering and ripening of fruit, and is available in an easy to handle, low dust pelleted form.Don't let that information confuse you, Richierich - the guidance I've given above in my previous response is pretty much textbook!