Hi--So wonderful that you are starting a garden for the butterflies! You may get addicted and start putting in new beds and expanding existing ones. The A. incarnata depending on soil and moisture can get pretty tall 3-4 tall and may need up to 3 feet width. A. tuberosa generally stays about 2 feet and may expand 2 feet or so. I plant my gardens pretty tight so that the there is plenty of cover for the caterpillars and places for them to pupate. I just make sure I keep enriching the soil with a steady supply of compost and organic fertilizer. The butterfly weeds will provide a wonderful nectar source as well as food for the Monarch caterpillar, which tend to be voracious in their later stages.

In order to be very attractive for butterflies, gardens need to have large drifts of nectar rich flowers, so that means having multiple plants all set next to each other.

Have fun!