Which fertilser is best for which plants?

alexemmersonuk · May 2023

Hi - relative beginner here.

I have a lovely garden with many flowers, mostly lupins, foxglove, delphinium, alliums, camassia, petunias and a few wisteria and fig trees (I know, a bit random haha).

I am only starting to realise that plants need feeding as well as watering and I am feeling really VERY confused and overwhelmed by the choice of different fertilisers.

I guess I am wondering, does it realy matter wcih one I use? Does it really make a difference?? Or am I OK to just use a general one for everything?

If not, which type is best for what please?
Thanks!
Alex

tesongo · May 2023

This is a very good question Alex. Thank you for asking. I am also interested in this issue.

Fairygirl · May 2023

I don't feed my plants as much as other people seem to do as it's better to keep the soil healthy. Overfed plants can be much weaker and less resistant to pests and diseases than plants which are grown harder.
However, for anything which is a heavy flowerer, like large flowered Clematis, I use tomato food, but mostly I use that for pots. I sometimes use one of the slow release granular foods at the start of the season for things like dahlias and sweet peas, which are greedy plants, and they get tomato food later in the year when that's been used up. Container plants need more attention than those in the ground.
For anything else, some slow release food in early spring is fine. I use Blood Fish and Bone, but I don't use it for everything in the garden - mainly when planting something new, then they just get on with it. The clematis get that at the start of the season if they're not already in flower.

alexemmersonuk · May 2023

@Fairygirl so how do you keep soil healthy? Do you mean change the soil?

Obelixx · May 2023

It's always best to "feed" the soil with applications of mulch from well-rotted garden compost and/or manure as this will feed the beneficial micro-organisms that interact with plant roots and improve soil fertility and plant health. Plants grown in pots need an annual top dressing and regular feeding as planting composts only have food for 80 to 90 days - half the growing season.

That said, you can give a tonic by applying a high nitrogen feed for foliage plants or high potassium and phosphorus for flowering and fruiting plants. These are listed as NPK on bottles or packs of fertiliser.

In addition, plants need some essential trace elements such as iron, copper and magnesium.

Look for rose, clematis or tomato fertiliser for high P and K levels. Seaweed based feeds contains the trace elements and Epsom salts can fix magnesium deficiency which often shows as yellowed foliage, especially in ericaceous plants. Look also for special feeds for ericaceous plants, citrus plants etc.

Fairygirl · May 2023

Yes - organic matter added regularly, as @Obelixx describes.

Old compost from containers is also useful, or bark for shrubs/trees - anything woody. Leaf mould is also an excellent addition if you can obtain leaves in autumn, and let them break down, although it can take a while for that to happen.

alexemmersonuk · May 2023

@Obelixx
@Fairygirl

Forgive my ignorance, but is there a difference between "soil" and "compost" or are the two used interchangeably?

Fairygirl · May 2023

Compost is man made -by allowing a mix of materials, ie greens and browns, to break down over time. All the material from plants dying back/deadheaded, plus things like fruit and veg peelings, eggshells and grass clippings are greens, and browns are things like cardboard, newspaper and some woodier prunings etc.
Soil is just earth - the basic stuff you'd have in the garden

alexemmersonuk · May 2023

@Fairygirl
that helps a lot! Thanks!

Slow-worm · May 2023

Random is good! Gardening is an art and we express it however we feel. 😊
I rarely feed either. Only tomatoes and agapanthus get some.
I let all the autumn leaves stay on the soil, and don't tend to cut things back until spring, so the plants which die back in winter just go back into the soil.
I don't mulch or compost either, though maybe I should a bit.
The birds fertlise a fair amount for me. 😁
My MIL has a beautiful fig, and never does anything to it.

Obelixx · May 2023

Figs are know to thrive in poor soil and are not alone in that but some plants - roses, clematis, other heavy flwerers etc - are gross feeders and need good soil or supplements.

Horses for courses.

As for "compost" it can be confusing. The stuff you buy in bags for sowing seeds, piotting on and general growing on is called compost and is usually made to a formula such as John Innes 1, 2 and 3 which are lam based or Levington's which is houmous based and now there's multi-purpose too. All have different levels of loam and composted waste materials but it would be more logical to call it planting medium and media as it is formulated for sowing and/or planting.

Garden compost is what you get when you pile up all your garden and kitchen waste so it breaks down and becomes usable material for improving your soil's texture and fertility. It is made by composting but isn't necessairly good for planting without some sieving and additions.

Which fertilser is best for which plants?

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