Monday 24 October 2016

Diarmuid Gavin: feed your greens

Putting on a floral summer show takes a lot of energy, so feed your plants to keep them in full bloom

Diarmuid Gavin

Published 28/06/2015 | 02:30

Seaweed can be used as garden feed
Seaweed can be used as garden feed
Watering can
Manure pellets for feeding plants
Soil renew feed

Our garden plants are vigorously growing, producing roots, shoots, foliage, flowers and fruit. They can't do this on an empty belly so it's a good time to consider what and why we feed them.

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Almost all plants photosynthesise, meaning that they use energy derived from sunlight to convert carbon dioxide and water into sugar. Alongside this they take nutrients and trace elements from the base they are growing in. Generally that's soil or compost, sometimes it can be water or, occasionally, in climates where the air is moist, some air plants thrive with no base material.

Our garden plants need nitrogen (N) for leaf and stem growth, phosphorus (P) for roots, and potassium (K) for flower and fruit. As well as these, small doses of calcium, sulphur, magnesium, zinc, iron, copper, boron and manganese are required. Plants aren't fussed where these nutrients come from, they just want them available in spring or summer.

Before you plant a garden it's important that you ensure a nutritious base for all plants. If done properly, with the addition of bountiful amounts of organic matter, it will improve the texture of any soil and ensure that any nutrients and trace elements which are locked in the soil become available for the roots.

Usually soil is pretty good with reserves of what's required. Poor plant growth can be due to factors such as drought, water-logging, soil compaction and weather damage. Adding organic material will also help to ensure that water is kept around the root-ball and available when required. Manure will loosen a compacted soil over time. It will slow down the leeching of food and water in a light sandy soil.

So, what do we feed our gardens in the middle of summer? Below I've identified a number of options, keeping the feeds as natural as possible.


A liquid-based plant drink will provide nutrients in a way that they can be absorbed immediately. You can purchase plenty of mixes from your garden centre but it's also easy to produce your own. Grow some comfrey. It has deep roots which stretch way down into the soil, grabbing loads of nutrients which other plants can't reach and storing them in its leaves. Harvest some leaves (wear protective gloves, the leaves can be irritating) remove flowers and stems, chop up the leaves and put in a container with a lid. Weigh the leaves down with a stone, add water, put the container in a cool, dark place and check every couple of weeks. When the liquid is dark brownish it's ready to use. Apply one part comfrey water to 10 parts water with a watering can to anything that is about to fruit or flower for a potassium-rich feed.


Poultry manures such as chicken or pigeon droppings contain higher amounts of N, P and K. They come in pellet form and can cause a bit of a stink as you sprinkle them in planting holes or around the base of established plants. Use gardening gloves. As with other animal-derived feeds (fish, blood and bone meal) they are slow to release their nutrients so apply in late winter or early spring, before growth starts.


Soil Renew is a natural and easy to use form of garden plant feeding. Full of micro-organisms and organic plant matter, it works with the soil's natural processes to boost its efficiency. It comes in pellet form, which is recommended you scatter once a year around the base of plants. You don't dig or hoe it in, relying instead on whatever lives in the soil to aerate, improve the drainage and make the locked-in nutrients available to the roots. I used it this year and am delighted by the results.


Seaweed fertiliser is more a tonic than an all-round feed (due to the lowish quantity of nitrogen and phosphorus). Along with supplying matter to condition the soil, it contains around 60 trace elements and nutrients, and some useful fungal and disease preventatives. It's available in liquid or dried form or is often used in coastal regions fresh from the sea as a mulch or dug directly into planting pits.

Make a plan

Where do you start with a planting plan? Provide Mount Venus Nursery in Dublin's Rathfarnham with some basic information and they'll do it for you. SEE: mountvenus

This week in the garden:

● Cut back the wandering foliage of hardy geraniums now to encourage some fresh floral growth.

● If you have a pond with water lilies, you will be aware that they can easily take over — the leaves dominating every inch of the surface of the water. Prune these back by about a third and remove the wet leaves to the compost heap.

● Continue your deadheading — roses, bedding plants, sweet pea can all be done this week. Anything that flowers repeatedly should be deadheaded to encourage more blossoms.

● If you’re going away on holidays, ask someone to water your pots and houseplants or set up a simple irrigation system. If you do this, move your houseplants outside and hook them up to it for the duration of your break. They will love the fresh air.

● It’s an excellent time to prune deciduous magnolias now, but keep an eye on retaining a graceful, natural-looking shape.

● It’s time to tie-in your blackberry canes now.

Grow your own organic veg

When Klaus Laitenberger came to Ireland, organic vegetable growing at home was in its infancy. Today, the perception that vegetable gardening is for hippies and retired old folk is quite outdated, and thousands of people are now growing their own food again.

Ireland has a unique climate and it took organic gardener Klaus a few years to adjust his growing techniques to this. He now produces a huge variety of vegetable seeds, from carrots and cucumbers to aubergines and radishes. A lecturer in organic horticulture at UCC, he continues to experiment with others to see if they can grow in all soils and conditions in our varied climate. My crucial tests for seeds are ease of growing, disease-resistance, crop productivity, performance in all climates and taste. Klaus’s products tick all of these boxes.

DETAILS: Packets from €2.80 at

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