Ask Mr. Smarty Plants

First, since you will essentially be creating a mini-meadow on the drainfield, you might like to read our How to Article, Meadow Gardening.

Annuals that will reseed themselves would be ideal since they won't produce enormous root systems.  There are several ways to find annuals native to Michigan that are deer resistant.  We have a Deer Resistant Species page with more than 340 species listed.  You can use the NARROW YOUR SEARCH option to select 'Annual' from LIFESPAN.  Although all the plants in the list are at least somewhat deer resistant, they aren't all native to Michigan; so, when you select 'Annual' from LIFESPAN, you should also select 'Michigan' from SELECT STATE OR PROVINCE.  This will give you a list of plants native to Michigan that are annuals and resistant to deer.  You can then check under the BENEFIT section on the species page to see if the plant attracts butterflies and/or other insects.  You should also check under GROWING CONDTIONS to make certain that plant's requirements match your site. 

Here are a few recommendations from that list:

Cleome serrulata (Rocky Mountain beeplant)

Croton monanthogynus (prairie tea)

Gaillardia pulchella (firewheel)

Rudbeckia hirta (blackeyed Susan)

Most grasses are perennials which means that their root systems are going to be more extensive, although they are not too likely to interfere with your drainfield.  One annual grass on this list is Aristida oligantha (prairie threeawn) and here are photos and more information.

You can find other grasses in the list by selecting 'Grass/Grass-like' under GENERAL APPEARANCE and changing LIFESPAN to 'All durations' in the NARROW YOUR SEARCH option.  Here are other grasses that you might consider:

Bouteloua curtipendula (sideoats grama)

Elymus canadensis (Canada wildrye)

Schizachyrium scoparium (little bluestem)

Sorghastrum nutans (Indiangrass)

Another approach is to go to our Michigan Recommended page where you will find a list of commercially available plants native to Michigan that are suitable for landscaping. You can use the NARROW YOUR SEARCH option with this list, also.  To determine deer resistance for these plants you can look under the BENEFIT section on the species page.

We can't help you with the vegetables because the majority of vegetables are cultivars of plants that originated somewhere other than North America and our focus and expertise here at the Wildflower Center are with plants native to North America. I suggest you contact your Washtenaw County MSU Extension Service for advice about planting vegetables over your drainfield.

Here are photos from our Image Gallery:

Cleome serrulata

Croton monanthogynus

Gaillardia pulchella

Rudbeckia hirta

Bouteloua curtipendula

Elymus canadensis

Schizachyrium scoparium

Sorghastrum nutans