I have a very large weeping willow, a very big white pine and another pine tree in my backyard that’s about 65 ft wide and 50 feet deep. I’ve been pretty successful getting a garden growing underneath all of them but the flowers in the gardens never seem to do as well as in my planters. I use granular garden fertilizer from Sheridan nursery which suggests applying it a couple of times throughout the season. I’ve done the early spring application and it suggests I should do another end of June. I’m wondering that with all the trees I need to increase the number of applications? I’d love your feedback. Thank you


Thanks for contacting the Toronto Master Gardeners.

What you describe in your backyard seems to be increasing shade conditions? It really has little to do with the amount of fertilizer you use. The plants/flowers that you have been growing are now getting less light than they originally did–are they perennials that have been growing in the same spot for years or do you plant new annuals each year? The quick answer to your question about the need to increase the number of (fertilizer) applications for your plants is NO. But you should consider amending the soil and being aware of what conditions your plants require. [However, plants in your planters will need an occasional addition of fertilizer].

You don’t mention where your planters are in relation to the other plants in your backyard garden; depending upon where you place the planters, the plants in them may be getting the sun that they need; in addition, if you replenish the soil annually in your planters, the plants would have what they need to grow well. Whatever plants you have growing under the trees–either annuals or perennials–are simply not getting as much sun as they need; increasing the amount of fertilizer that you use will not help. Some plants need full sun; others prefer part sun or shade. Each type of plant has different light requirements. However, all plants need good soil.

One of the most important principles for growing plants is to feed the soil; the soil will feed the plants. Have you amended the soil where these plants are growing with compost or leaf mulch? Feeding your soil with organic matter is easy but essential;  here is information on how to do so. Following some of these suggestions will improve the soil without the use of purchased fertilizers and your plants will most likely do better.

Another principle for successful gardening is planting the right plant in the right place. If the light conditions have changed over time in your garden, plants that require full sun may not be doing as well as they once did due to increasing shade–you may have to consider using plants that can be grown successfully in part sun conditions.

You mention that you have a willow tree in addition to a couple of pine trees. Willows tend to have spreading shallow roots which  may be interfering with the growth of your herbaceous plants. Nevertheless, amending the soil around the plants on an annual basis by simply using compost/mulch will be helpful in sustaining optimal plant growth for your plants.

If you adopt these suggestions for feeding the soil in your garden and making sure that your plants are placed where they will grow best, your plants will thank you with good growth.

Happy gardening!