Growing Purple Carpet Lemon as a Ground Cover in Zone 3
Answered by: Inge Poot
Question from: Monique van Leeuwen
Posted on: April 12, 2010

We have about 1500 square feet of clay soil with North exposure that I would like to cover with the Thymus praecox articus ‘Purple Carpet’. I am hoping that this hardy Thyme will help us minimize the spring mud on our acreage and make this area look more attractive.

I am planning to use Roundup to kill the weeds and rototill as soon as the mud has dried up. To make sure I give it my best shot I would really appreciate it if you could answer my questions below (I hope I’m not asking too many).

1) How many plugs do you suggest I order to cover 1500 sq.ft. and how far apart they should be planted?

The ideal would be 6000, to be planted on 6" (15cm) centers. If you are willing to keep down the weeds for a year, maybe by mulching around the plants, you could get 1500 plugs and plant them on 1 foot (30cm) centers.

2) How many inches of topsoil should I put over the rototilled clay and should I work the soil into the clay or just cover?

It all depends on how fertile the clay soil is. If it is thick yellow clay with no nutrients, then 2 to 4 inches (5-10cm) of topsoil should be rototilled into the top layer of clay. If it is black clay, you may not need any topsoil addition.

3) Is there anything else I should incorporate into the top soil?

Yes! Sharp builder’s sand is essential in clay soil. Mix it in so that the top 4 inches are about 50% sand.

4) Which fertilizer do you recommend?

Well-rotted manure works very well. It add organic matter as well as nutrients.

5) What is the suggested watering regime?

The first week water twice a week unless you had rain. Water deeply to encourage roots to go deeply and thus be more resistant to drought. After that water only when the top half inch (1cm) becomes dry. Mulching is always a good idea for young plants especially.

6) Should I mow the thyme after flowering?

You can, but you do not have to.

7) The last two years we received very little snow. Is it suggested to mulch the ground cover to be on the safe side? If yes, what would you use?

Yes, a winter mulch to cover the whole plant is great for holding whatever snow you do get. It also protects the plants from dessication by the sun, when the roots cannot take up water, because the ground is frozen. Straw is better than old hay, because it will contain fewer weeds seeds. Evergreen boughs are best, but you may not have any available until after Christmas!

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