Marigold Bonanza Bolero - Fertilisers for flowers
What use fertilisers?	While some question the value of using fertiliser in gardens we take a look at the effects of different fertilisers on marigolds grown in pots and in particular try to find out what increases the number of flowers. The basic questions are: Do you need to use any fertiliser at all, especially if you have a good compost? How much can a fertiliser increase flowering in these conditions? Will any old fertiliser do or do you need to use the right one?
What does the plant need?	Most plants need to be provided with up to 19 different chemical nutrients for normal growth. Most of these are adequately supplied in soils or, by the addition of fertilisers during manufacture, in a good quality potting compost. Carbon, hydrogen and oxygen which make up most of the substance of a plant are supplied free of charge in fresh air and rainwater. The key plant needs supplied by most fertiliser materials are nitrogen (N), phosphate (P) and potash (K). You will often see N fertilisers recommended for leafy plants, P for promotion of root development and K for flowering, certainly an oversimplification of the subject, but it does at least suggest that the type of fertiliser you use can make a difference.
What are we comparing?	1. We have planted marigold seedlings into a low nutrient seed compost and a multi-purpose peat-based compost. 2. We are comparing high N, high P and high K liquid feeds with a high everything liquid feed (high N, P and K) 3. We are also testing a controlled-release fertiliser to see how it compares with the liquid feeds. 4. And finally we look at an 'organic' Fish, Blood and Bone powder fertiliser to find out how well that works.
How the plants are being grown	Seedlings of French marigold Bonanza Bolero were transplanted into 9 cm (3.5 inch) pots using either a seed and potting compost (used only to get the plant started) and a multipurpose compost (both peat-based) on April 26. By May 10 all plants had grown to the stage at which the first apical (topmost) flower bud was just showing on most of the plants. The liquid feeds are being applied approx every 5 to 7 days. The number of flowers on each plant will be counted at end May and then every two weeks through the summer.
Summary of the treatments	In all, 12 different treatments are being compared. They are: Started in a multipurpose compost, transferred to a low nutrient seed compost. No added fertiliser. Started in and transferred to a high nutrient multipurpose compost. No added fertiliser. Seed compost, high potassium (K) liquid feed Seed compost, high phosphate (P) liquid feed Seed compost, high nitrogen (N) liquid feed Seed compost, high NPK liquid feed Multipurpose compost, high potassium (K) liquid feed Multipurpose compost, high phosphate (P) liquid feed Multipurpose compost, high nitrogen (N) liquid feed Multipurpose compost, high NPK liquid feed Seed compost mixed with controlled release fertiliser Seed compost mixed with Fish, Blood & Bone fertiliser Multipurpose compost mixed with controlled release fertiliser Multipurpose compost mixed with Fish, Blood & Bone fertiliser Technical Note: High N, P and K fertilisers were based on NPK ratios of 3:1:1, 1:3:1 and 1:1:3. The controlled release fertiliser was Osmocote used at 3 gm per litre of compost: Fish, Blood & Bone (J A Bowers) was used at 8 gm per litre of compost to provide N, P and K at rates similar to the Osmocote. The High N, P and K liquid feed was Chempak Formula 3 (NPK 20:20:20).
Predicting the results	Marigolds are vigorous 'hungry' plants. Those planted in multipurpose compost should therefore do better than those transferred at an early stage into a seed compost.
	Normally you might expect more fertiliser to mean more flowers but not necessarily early in the season because the less well-fed plants may start flowering earlier and show more colour earlier. How often have you seen or heard a recommendation to 'use a high potash fertiliser for flowers'? Well we will be able to see with marigolds if the high K fertiliser does actually mean more flowers compared with high P and high N - or does a high NPK give an even better result? How good are the slow (or controlled) release fertilisers in this situation? Since they release nutrient steadily day by day during the season they could avoid the possible disadvantages of liquid feeding where the plant gets a weekly 'pulse' of feed. But remember that the controlled release is aimed at a period of six months at normal temperatures. Release is more rapid at higher temperatures. Complicated, isn't it? Results will be posted as they become available during the summer.
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