Gardening Tips: Soil Fertility Rights (and Wrongs)

Editor’s Note: The Spectator is reaching into Michelle Smith’s gardening column archive for some weekly advice that is as relevant now as when it was first written. (This column last appeared on 16 June 2021)


What to do this week

This week, I would like to talk about adding fertility to the plants in your garden. Obviously the best way to have good fertility is to have good, rich soil to begin with. There is no substitute for good soil. But if your soil is still a work in progress, or if you have certain plants that need a little top up, there are ways you can add fertility.

I am thinking about this now because I am adding compost to my garlic. The whole allium family — which includes garlic, onion, green onion, leeks, shallots and chives — are all very heavy feeders. They can do with some top dressing at this point in their growth cycle. The treatment can be especially effective if you can time it for just before a good rain, so the added fertility gets washed down where it is needed.

Compost tea. (Madeline Yakimchuk photo)

Compost tea. (Madeline Yakimchuk photo)

You don’t want to fertilize the allium family later in the season because that is when the plants are trying to harden off and form their bulbs. Right now, these plants are in an active growing state, really sucking up nutrients, so top dressing your onion and garlic beds with a good dose of compost would be very effective now.

Another option is to use compost tea. My method is to take a shovel of well-aged compost, manure or plant based, and put it into a feed sack or something similar. Basically, I am making a giant teabag. I then let this sit and steep in a five-gallon bucket filled with water. Leave it for a day or two. The resulting water is a really quick fertilizing boost.

There are a lot of ways to make a compost tea. This method is simply how I do it. Some people throw a shovelful of compost into a bucket and add water without bothering with the filtering sack. Some people leave it in the sun for days, covered with a loose lid. Some people make tea with seaweed — even old, rotted seaweed. Most of us refill the bucket with water, like using the same teabag a few times, keeping the tea brewing and always ready for use. This tea can sit out in the sun for long periods, getting more rich as time passes, but you might want to be careful about attracting mosquitoes. Place the lid on the bucket lightly, perhaps with a rock on top to keep it from blowing away. That should discourage mosquitoes and should be done whether your bucket is in the sun or shade. It will also prevent your compost tea from evaporating.

There is one important caution when it comes to compost tea: the Organic Standards Association recommends you not use compost or compost tea on any plant that is going to have its leaves eaten within the coming six weeks. This means you would not use it on spinach or lettuce this time of year, or anything with above-the-ground leafy parts you are going to consume in the near future. The reason for this is that all compost is very rich in bacteria (that’s why plants love it) but that can include bad bacteria, which is not good in your salad bowl. The chances of a serious problem are slim, but these standards are in place to protect people. There is no problem using the tea on leafy veggies you are not going to consume for weeks, or on other veggies.

Some people get very particular about their compost tea. They may insist on using only plant-based compost, or connect an aerator to the bucket so the liquid is aerated while it steeps. The biodynamic movement is particularly known for this, and if you want to get into that, I have no problem at all with it. I prefer the simple method, though, especially when something simple works just fine.

Another fertilizer I use regularly, most often on seedlings rather than in the actual garden, is commercially available, concentrated liquid fish fertilizer. You can get it at any good garden center. It is fairly high in nitrogen as well as phosphorous, so must be used with some care. Read the instructions about how much water to mix with the product before using it on plants. It is important not to over-fertilize by not diluting the concentrate sufficiently. (You can burn your plants.) It is also important not to fertilize too often. Every couple of weeks is sufficient.

These add-on fertility techniques are no substitute for building your soil, which you should be doing in parallel. Think of these treatments as maintenance, while the building of soil tends to take place in spring and autumn. These techniques are just a little extra for a few seedlings, while they grow, or for plants like allium that are heavy feeders. It is too early for squash, but they are also heavy feeders, and can also use extra compost when the time comes. Also for later, basil can sometimes use a little help. Herbs don’t generally need fertilization. In fact, they can taste a little bland if you do fertilize them. They produce those aromatic oils under stress, usually, and shouldn’t be too well fed or happy. However, if you like to pick basil leaves, forcing it to grow more, sometimes several times during the summer, that is a bit too much to ask of any soil. The plant will need a bit of fertilization, every few weeks, as the summer progresses. Since you are eating the leaves regularly, when the time comes, you should use fish concentrate on your basil, not compost tea.



Market gardener, farmer, workshop leader, seed-saver, political candidate and mother, Michelle Smith has spent over 30 years coping with the challenges of our bioregion and in the process has built a store of practical and technical knowledge. The Inverness resident has served on the board of Seeds of Diversity Canada and represented Alternative Producers with the Federation of Agriculture but can do nothing about her hair. She is pictured with a head of Club Wheat, a seed that shares her approach to hairdressing.




Backyard food gardener Madeline Yakimchuk caught the food-security bug in the early ’90s through Cuba’s Urban Agriculture Department, taking her first permaculture course and planting her first garden. She can often be found discussing food security, nurturing a plant-based lifestyle or trying to give away vegetables. Professionally, she is GRYPHON media productions but sometimes uses la bruja in her volunteer work, most notably in managing the garden column, which begins life as a telephone interview.