Adding fertiliser can boost your blooms and increase crop yields

The weather in March is unpredictable to say the least: one minute we’re in T-shirts, the next moment, we’re wrapping up in full waterproofs. Whatever the weather, one important thing to remember this month is not to get carried away with direct sowing and planting as we could still get a hard frost well into mid-April.

I like to sow quick-maturing crops like spinach and lettuce in modules to grow sturdy plants, then plant them out so the young plants have more chance of survival in the cold soils and can resist some pest damage. March is also a good time to feed your fruit trees and shrubs, especially patio fruit in containers. Using fertilisers can help you with the success of your crops. Choosing the right type of fertiliser for the job is important as there are lots of different ones available which will have very different effects on your plants.

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What is a fertiliser? Fertilisers are concentrated sources of plant nutrients that are added to the growing media. They are used to improve plant growth and yields. They are mainly in the form of powders or granules and most contain major plant nutrients. For those of you who have used fertilisers before, you may have noticed that the main nutrient contents are Nitrogen (N), Phosphorus (P) and Potassium (K) which are needed by plants in larger quantities. Additional nutrients are needed in certain fertilisers and some - known as trace elements - are needed in smaller quantities.

Nitrogen is essential for green leafy growth (vegetative growth) plants grown for their leaves, including cabbages and kale. For root and shoot growth Phosphorus is a vital nutrient, especially at seedling stage. Potassium is needed for successful flowering and fruiting and helps to promote hardiness.

Why use fertilisers? It is not always necessary to use fertilisers if you have a healthy soil, but adding a fertiliser may produce a better display of blooms or a higher yield of produce from edible crops. Fertilisers can also be used if plants are showing signs of nutrient deficiencies. Remember, having a healthy soil structure and pH can often help to prevent plant nutrient deficiencies. Adding manure, mushroom compost and composts will help with this.

Choosing your fertiliser There are two main types of fertilisers: organic and inorganic (man-made). At Harlow Carr, I prefer to use organic fertilisers because they are much more environmental friendly as they are derived from plants or animals. Organic fertilisers can contain everything from bone meal, hoof and horn, dried blood and fish blood and bone to poultry manure pellets, liquid nettle, comfrey and seaweed feeds.

Inorganic fertilisers are synthetic, artificial forms of plant nutrients or some are mined or quarried materials. Inorganic fertilisers usually come in more concentrated forms and work much faster than organic fertilisers. The amount of nutrients that are supplied by the fertiliser in inorganic fertilisers are expressed in terms of percentage of the contents such as %N, %P, % K. Inorganic fertilisers include Growmore, Miracle-grow triple Superphosphate and Sulphate of Ammonia.

Both organic and inorganic fertiliser can be found in different forms as follows:

* Compound fertilisers supply two or more different nutrients. They may be balanced or may supply more of one nutrient than the other.

* Straight fertilisers contain only one major nutrient and are beneficial if you need to provide different types of nutrient throughout the year.

* Slow release fertilisers dissolve slowly and are released by soil micro-organisms which are dependent on soil temperature; these are normally organic.

* Controlled release fertilisers are also slow release but release their nutrients in a controlled way

* Quick release fertilisers dissolve quickly in water before or after applying.

There are different ways to use fertilisers. This will depend on the fertiliser you are using, such as top dressing (applied to the soil surface), base dressing (applied and worked into the soil or into potting compost), liquid fertilisers (dissolved or diluted and watered on, avoiding contact to the plant), foliar feed (dissolved or diluted and applied to the leaves).

When applying fertilisers, always read the manufacturer’s instructions to see the recommended rate before applying; make sure you don’t overfeed and always wear gloves when handling.

Why not pay a visit to RHS Garden Harlow Carr to get expert advice and to see what we are doing in the kitchen garden this month.

With thanks to Joe Lofthouse, Horticulturist at RHS Garden Harlow Carr

Jobs for the Week

* Start to sow crops such as tomatoes, brussel sprouts, broccoli and summer cabbages in modules in the nursery

* If you haven’t already, get your fruit trees planted this month

* Continue to improve drainage of heavy soils by working in organic matter

* Prepare seed beds

* Finish off pruning your soft fruit.


March 21: RHS Free Tuesday Visitors have the chance to enjoy the beautiful surroundings of the RHS’s inspirational four gardens in spring - for free!

March 25-26: Mother’s Day Weekend Join us on Saturday and make mum a scented lavender bag or bring her for a walk in the garden on Sunday to enjoy a free hand massage from 1pm – 4pm and learn about aromatherapy. Take in the spectacular spring bulb displays – from daffodils and hyacinths to scillas and trilliums – and perhaps a coffee and cake at Bettys Café Tea Rooms next door. Normal garden admission applies.

Until March 28: Bath House Gallery – Wool & Textiles Showcase Pop along to the historic Bath House at RHS Garden Harlow Carr for the cosiest event of the year! Discover work by talented local wool and textile artists, from wonderful things to wear to gorgeous gifts for your home. Embroidery, felt and leather work will all be on display. Normal garden admission applies.