Ultimate Guide To Summer Fertilizer

Ultimate guide to summer fertilizer

Last Updated on February 18, 2024 by Kimberly Crawford

Even if your garden soil is good and balanced, there’s no doubting the growth-enhancing effects of fertilizers and the extra vitality they bring to flower and foliage plants, edible crops and lawn areas.

Anyone wanting to get the best garden displays should have a selection of fertilizers ready to hand through summer. Indeed, away from the border they become essential where composts hold only limited nutrients for basket and container plants.

Overwhelming choice

The choice of fertilizers on garden centre and DIY store shelves however, can be overwhelming. With such a selection it can be hard to decide what is best to buy for your plants. General purpose fertilizers with balanced nutrient content offer an ‘all purpose’ solution for no-fuss gardeners looking to keep things simple.

You could get by with a granular all purpose feed for borders and a liquid version for pots, but there really is no ‘one-size fits all’

Getting to grips with basic plant nutrient requirements will help you make the right fertilizer choice for different parts of the garden and for different plants. Fortunately there are very few poor performing fertilizers on the market. Even after 20 years of gardening, I’m still more often guided by price and multi-buy deals than performance claims when it comes to stocking up on fertilizers. Just stick to a respected brand, follow the dosage instructions and you won’t go far wrong.

Getting started

Nitrogen (N), phosphorus (P) and potassium (K), are the three key bulk nutrients of any good fertilizer, and each supports different growth on a plant. An NPK ratio will be stated on all fertilizer packets, though other nutrients and trace elements such as iron, magnesium, and copper, are often listed. But even with an understanding of NPK this still leaves a range of options to work through – Organic or inorganic? Controlled release or fast acting? Liquid, granule or pellet?…

Quick fix or controlled release?

As a general rule, faster growing plants require more feed to support optimal growth. Liquid feeds have the advantage
of being immediately available to plants. However, they don’t stay in the soil for long and easily wash out if applied before rainfall, or if frequent watering follows.

Offer regular doses of liquid fertilizer such as Phostrogen All Purpose for hungry flowering plants like seasonal summer bedding in pots, baskets and borders.

Patio grow bags and greenhouse vegetables – tomatoes, peppers, cucumbers and the like – also respond well to regular liquid feeds, perhaps weekly during peak growth.

Grow More 5010 All Purpose Fertilizer 20-20-20, 25-Pound
via Amazon

Standard granular feeds are longer lasting compared to liquid feed. A balanced fertilizer such as Growmore or Vitax Q4 can be applied from spring onwards every six weeks or so, and can also be added to soils and compost when planting. If you applied granular feeds as a spring top dressing, now is the time to make a repeat application for continued plant performance.

Controlled release granular feeds go further still, allowing for the most laid back approach to feeding border and container plants, taking you through the whole summer season with one application. Gro-Sure All Purpose tablets for example, mixed in with compost at the planting stage, lasts up to six months, and new Incredibloom specially formulated for vegetables (from
Thompson and Morgan) is said to last up to seven months.

Is organic really organic?

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Organic fertilizer ingredients were once of living origin rather than organically produced, so organic gardeners should check labelling before buying – it can get quite confusing as many organic feeds are not certified for organic use.

The term takes in feeds such as animal manure and garden compost, down to concentrated forms such as blood, fish and bone and seaweed extract. Weight for weight, inorganic fertilizers offer the highest macro-nutrient content compared to organic options and are often faster acting, but organic feeds can be richer in trace elements.

Some brands such as Empathy are combining chemical fertilizers (for guaranteed results) with health-enhancing organic extracts such as liquid seaweed. Whichever fertilizers you opt for this summer, always wear gloves when handling (or at least wash bare hands afterwards) and do not apply more than the stated dosage on packaging. Too much feed can lead to soft growth, open to attack from aphids and other sap suckers.

General Purpose

If you want an all round feed for trees, shrubs and perennials in the border, a dry mix or pelleted balanced, general fertilizer like Vitax Q4 or Fish, blood and bone supplies a good level of phosphorus, potassium and nitrogen. These are scattered around
plants in spring and every six weeks in the growing season.

Soluble general purpose food, which you mix with water (such as Miracle Gro or Phostrogen) is fast acting but can run
through soils quickly, meaning you’d have to be applying it to border soils every couple of weeks. But it could be used as a quick fix pick-me-up solution when border plants take a sudden turn for the worse.


AS well as benefiting from an acidic (ericaceous) soil/compost, the likes of rhododendrons, camellias and blueberries all perform better with an ericaeous feed. In the border these plants will benefit from an application of sulphate of ammonia or sulphate of potash in spring and early summer, and in pots, they should have slow-release granules mixed in the compost or be regularly given a liquid ericaceous feed.


We all want lush, weed-free lawns and summer lawn feeds offer fast results. Use from spring through the season but don’t use much past mid-August, you want growth to slow again in autumn so you can put the mower away for winter. For really weedy lawns opt for an all in one lawn feed and weedkiller. 


It is legal to collect seaweed from a public beach provided it is detached from the plant

SEAWEED solutions like Maxicrop and Vitax liquid seaweed can help prevent and cure nutrient deficiencies in most plants – often they can be applied as a foliar feed, sprayed onto the leaves and taken up by the leaves.

Heavy use of liquid feed in grow bag tomatoes can prevent magnesium uptake by the plants, and nutrients can be locked out by deep rooting plants in high pH soils. A foliar feed of liquid seaweed will rectify both. Popular fertilizers, like Tomorite and Empathy, are now available with added seaweed extract, so you have the benefits of seaweed at the same time as a fertilizer application.


WITH the big rise in grow your own, vegetables are well catered for in the fertilizer market. Crop specific feeds like Vitax Organic Potato & Vegetable feed are fairly long lasting – they can be applied ahead of sowing/planting, and once again midway through the crop. Suphate of Ammonia is a high nitrogen feed and is best for leafy vegetables and salads.

Fruit & Flowers

SOFT fruit, fruit trees and perennial flowering plants benefit greatly from a spring application of granular or powdered Sulphate of Potash, which is high in potassium. Fast growing annual crops and floral bedding respond very well to regular high potash liquid feeds through summer – tomato feed brings great results in flower pots and borders too!

Anyone wanting to get the best garden displays should have a selection of fertilizers ready to hand through summer. Indeed, away from the border they become essential where composts hold only limited nutrients for basket and container plants. #gardentips #garden #farmfoodfamily