Organic potting soil mixes and organic fertilizers for balcony gardening

Asked December 30, 2018, 2:16 PM EST

This past growing season I grew 7 tomatoes and 2 peppers in 26.5 liquid gal. (24 " wide) plastic pots with LeafGro as potting soil. I was not satisfied by the growing quality of the LG, as it seems to be deficient in certain nutrients. I bought some Neptune's Harvest, a mainly organic liquid fertilizer, but didn't end up using it. I was going to get some rock dust, but didn't end up using it either. I find most potting soils to be too porous and light - I've heard others report they dry out too quickly in the pots - even in those for the tomatoes. That's one reason I decided on very large pots - to minimize dehydration. During hot periods, I'd water every 2 - 4 days. Though I harvested some fruit, a couple of plants didn't bear any, or very little. I want to use compost in a mix, but even if I bought it at a nursery I could only get it by the yard and loose, which would create some transport issues. What other ingredients would you recommend like peat, moss, coconut fibres, worm castings? I think LeafGro is sterilized, which may account for its ineffectiveness, but may be useful in small quantities. Even mixing the liquid fertilizer with the soil ingredients could be worth trying. Do you know any nurseries or garden suppliers that would carry these ingredients? What proportions of the ingredients in a mix would you recommend? I've also thought of taking about half of the old LeafGro out of the core of the pots and leaving the rest in the perimeters, so I don't have to shlepp so much potting soil into and out of the balcony. The tomatoes and peppers had not grown very large root systems, so hopefully I can find ingredients that will promote that. Thanks for your advice. Best, Hanson Gildemeister

Montgomery County Maryland vegetables tomatoes in containers plant care

2 Responses

LeafGro is a good container growing medium but, as you discovered, it does not supply sufficient nutrients for a tomato or pepper crop. Fertilizing every 2-3 weeks with a liquid fertilizer would be fine. Follow label directions. You can also incorporate a complete analysis fertilizer, such as cottonseed meal, in the containers.

You could increase the weight of the containers while increasing the nutrient and water holding capacity of the LeafGro by mixing in some fertile garden topsoil- no more than 5-10% by volume. However, you would be introducing weed seeds, and possibly soil-borne p[lant pathogens. A better solution would be mixing compost 50:50 with a soilless growing medium (ex: Pro-Mix, Fafard, Sunshine Mix). These mixes contain several of the following ingredients: peat moss, perlite, vermiculite, coir, compost, bark fines, etc.) They have a small fertilizer charge so you'll have to fertilize to produce healthy crops.

LeafGro is not sterilized. The material is re-inoculated naturally with microorganisms after the composting process and is thus biologically active. It;s fine to re-use LeafGro but always add fresh compost and other growing media because the compost becomes physically degraded over the course of a growing season.This leads to a greater number of very small particles and reduced aeration.

There may be other reasons why your plants are not performing as well as you'd like. Most tomato and pepper plants grow fine in 5 gallon containers- one plant per container.Tomato and pepper require 6-8 hours of direct sunlight. Your balcony may experience high, drying winds and very high temperature during parts of the day which can greatly reduce flowering and fruiting. Consider installing an automated drip irrigation system on a battery timer to supply water consistently.

Hello jt,

Thank you for your response and suggestions. I like the idea of a 50:50 mix of compost and a soilless growing medium. Since I can't get compost in small quantities, I decided to talk to a representative of Miracle Gro. She suggested their organic raised bed mix (which includes compost) combined 50:50 with their org. potting soil mix (soilless growing medium).

Plants last year developed leaf deformities from the LeafGro, so this year I will take at least half of it from each pot and replace it with the above-mentioned potting mix.

Then add some liquid fertilizer to it after planting the tomatoes and peppers. The only concern is they get less than 6 hrs of sunlight daily, which could have been the cause of the deformities. But one of my house plants got them too.

Thanks anyway for your advice.