The following benefit from using fertilisers:
- Seedlings and cuttings
- Houseplants
- Plants in containers: fruit, vegetables and ornamental plants
- Fruit and vegetables in the ground unless using no-dig method
- Sick plants and plants showing nutrient deficiencies. Identify the cause first. Consider soil analysis or specialist leaf-tissue analysis for high value plants or crops
Feeding seedling and cuttings
There is a limited amount of nutrients available to plants in peat-free seed and cutting composts. Young seedlings and cuttings raised in peat-free compost benefit from early feeding – once the seedlings develop the first seed leaves and cuttings begin to grow.
Ideally, use a higher nitrogen (N) and lower potassium (K) feed, such as Elixir Gardens High Nitrogen Liquid Plant Food (20–0–10). However, using a general-purpose fertiliser with similar nitrogen (N) and potassium (K) values, for example: Miracle-Gro® All Purpose Concentrated Liquid Plant Food (7–3–5) will still help. Check the label recommendations carefully as young plants and seedlings usually require a weaker concentration of fertiliser to avoid damage.
Delay using high potassium fertilisers such as tomato feed that to encourage flowering and fruiting until the plants are well developed and producing flower buds.
Feeding plants in containers: fruit, vegetables and ornamental plants
Plants growing in containers need feeding to perform well. The potting compost available in garden centres provides optimum amount of nutrients for about six to eight weeks, but after this you’ll need to start feeding. If you make your own potting compost, the soil and organic matter in the mix should provide enough nutrients in the first growing season, unless you’re growing fruit and veg.
Liquid feed the following with homemade or organic fertilisers during the growing season (April to September). How often depends on the fertiliser you use, but below is an approximate guide.
- Fruit and vegetables every two weeks, or weekly if using homemade feeds
- Bedding plants for summer colour once a week
- Ornamental plants such as trees, shrubs and perennials once a month
- Undemanding plants, such as olives and bay trees, once a month
- Ericaceous (acid-loving) plants, such as blueberries, camellias, azaleas and rhododendrons, once a month with ericaceous fertiliser or seaweed feed containing iron
How can I reduce the need to liquid feed containers?
To minimise liquid feeding, which can be time consuming, mix an organic fertiliser into the potting compost before planting up your pot. Alternatively, you can also scatter it over the surface (known as top dressing). There are some specific organic products designed to add to potting compost . Check label for details of how to apply.
Choose plants for containers, that need only feeding occasionally. These include ornamental grasses, drought tolerant shrubs and Mediterranean herbs.
Feeding plants growing in the ground: fruit and vegetables
Mulching regularly (at least once every three years) with organic matter can deliver all or most of nutrients fruit and vegetables need to give you plentiful crops. Try the no-dig approach by avoiding soil cultivation and applying 5cm of mulch each year.
You can also use green manures to boost soil fertility by sowing long rooted plants to draw nutrients from deep in the soil and those that fix-nitrogen.
If you garden on free draining sandy or chalky soils, or grow hungry crops such as brassicas, additional fertilisers may be needed. Use homemade or organic fertilisers, such as fish, blood and bone, seaweed or comfrey-based feeds since these reduce environmental impact.
Feeding houseplants
Houseplants rely on regular feeding for healthy growth. How much feed depends on the type of plant. Most leafy plants enjoy feeding with a liquid general-purpose or houseplant fertiliser once or twice a month from March to October.
Orchids need a specialist liquid feed that’s weaker than others, while cacti and succulents enjoy feeding once a month with tomato feed or specialist cacti fertiliser. Feed these during the main growing season April-September.
Check out our individual growing guides for more details on how to feed different groups of houseplants.
Feeding sick plants and nutrient deficiencies
It is a common belief that poor growth is caused by a lack of soil nutrients and that applying fertiliser is the solution. The results of our Soil Analysis Service suggest that phosphorus, potassium and magnesium shortages in cultivated soils aren’t common.
Disappointing performance and leaf symptoms are often due to poor establishment after planting or weather related factors. These include roots drying out or becoming waterlogged which limits the uptake of nutrients present in the soil. In this instance, improving the soil and repotting plants in containers can sometimes help.
Some symptoms indicate a lack of nutrients. Certain groups of plants, such as tomatoes, raspberries and ericaceous (needing acid soils), are more prone to this than others. To help you identify when plants aren’t getting enough nutrients see our nutrient deficiencies webpage.