I have a very large maple tree on my front lawn. It is hard to maintain grass so I covered part of the lawn with soaked cardboard then shovelled 2-3 inches of mixed soil on top. My questions are: 1. Can I start to plant or do I need to wait 3 months for the cardboard to decompose? 2. If I can plant now. Can you suggest a perennial plant that I should buy and plant that will spread and survive this type of new garden that has limited sun due to the large maple tree?
thank you very much,
Thanks for getting in touch with the Toronto Master Gardeners.
Growing grass and plants under your large maple tree–most likely a Norway maple (Acer platanoides)–is definitely a challenge. Not only does the tree leaf out earlier than native maples, its root system is quite shallow and it’s leaves dense. The area that you have dug up is probably on the north side of the tree, which would get very little sun. Do you plan to get rid of all your grass or are you mainly concerned about the area that you have covered? You’ve mentioned that you would like to grow native plants in the area.
To answer your questions: (1) The cardboard and paper will not decompose that fast and can create an anaerobic state underneath it which kills the beneficial organisms in your soil. You are best just cutting everything very short and using several inches of mulch to block out sunlight. You can start to plant anytime; perhaps you can add some more compost as well. What you have done is an excellent way to convert your grassy area into a garden–do you plant to continue to transform the grassy area into an area with a variety of plants? If so, you may use at least 4-6 inches of organic matter (soil, compost, etc.).
(2) The heading of your request mentions ‘native plants’; your question requests a ‘perennial plant….that will spread and survive….. Are you looking for a ground-cover? Is height an issue? Do you want more than one kind of plant?
There are many groundcovers that you can consider. Here are some suggestions; although the list includes some attractive groundcovers, none are considered native. The most effective and quick-growing would be some of those listed at the bottom of the attachment: Ajuga (bugle weed), Lamium (deadnettle) which have variegated leaves and spring flowers; Geranium macrorhizum, and Pulmonaria (lungwort) which flowers in the spring and has interesting foliage.
And there are a couple native groundcovers that you can consider: Asarum canadense (wild ginger) and Geranium maculatum (wild geranium).
Lawn grass is a high-maintenance plant–there are many low-maintenance plants that can be used in the area around the maple tree. You might want to consider putting in a ‘pollinator’ garden in that area–it would be lower maintenance once it is planted. Here is some information that the City of Toronto has about creating one–many native plants are suggested for the colorful garden.
All the best in transforming the area under the maple tree.