What is the Best Raised Bed Cover Crop for Summertime?

We’ve had a nice, long, cool spring this year in my neck of the woods.  But now it’s getting to be pretty hot.  It won’t be long until we start to lose many of our spring crops to the summer heat.  At my house, it’s time to make up our minds about how we’re going to handle the heat out in the garden this year.  There are lots of decisions to make – here’s a list of the summer options we usually consider for our garden:

Keep the tomatoes?  Sometimes we keep watering these guys, and encourage them to limp through the heat. Pollination stops when the temperatures stay above 95 during the day and 80 at night, but sometimes we keep them alive through the infertile summer so that we have big, established plants ready when the temperature drops again in the fall.  We’re not too crazy about the varieties we grew this year, or about the performance of the individual plants.  So, we’ll probably cut them out this year.  We’ll start another round of seedlings in July, so that we have some fresh plants ready in the fall.

Provide shade for the keepers?  If we do decide to keep tomatoes, beets, chard, calendula, or other spring crops, we typically try to arrange some afternoon shade to help them get through the intense heat in July and August.  My favorite method is to build temporary bamboo trellises on the south and/or west facing sides of the bed, and plant the trellises heavily with pole beans.  The beans take the brunt of the afternoon sun, and work as a green shade cloth to protect the more delicate plants down in the bed.  Malabar spinach works the same way.  Sometimes we just use a lightweight shade cloth from the local nursery.

Plant again for summer?  Eggplants, okra, sweet potatoes, hot peppers, watermelon, etc.  There are plenty of edibles that do fine through the summer heat, even here in Austin.  When we keep a full summer garden, we have to water more often than we would like to.  And there are always plenty of pests that show up in the summer to prey on any of the plants that are suffering from the heat.  We have many projects going on at home this year, so we’re leaning away from a big summer garden this time around.

Throw a chicken party?  If we decide not to keep many spring plants, we sometimes turn the chickens loose and let them spend a few days taking out the spring garden for us.  This is like a huge party for the chickens, who have been ogling the beet greens and kale day in, day out, for the past few months.  There are a few plants that we cut out ahead of time because they’re not good for the chickens to eat, but otherwise it’s a chicken smorgasbord and it’s probably their favorite time of the year.

Cover crop?  In beds where we aren’t keeping any spring crops and we aren’t planting for summer, we try to do some cover cropping.  Occasionally there has been a situation where it didn’t make sense to use cover crops for one reason or another – because we were working on the bed or moving the soil.  In these cases we covered the soil well with a good organic mulch to keep the sun off of the soil.  For the mulch, we have used pine straw, biodynamic hay, and leaf litter from our many elm trees.  My favorite solution for a dormant bed is to cover crop.  The next best thing I’ve found is to put down a good half inch of fresh compost and cover that with an inch or two of pine straw.  The pine straw seems to hold moisture in the soil more effectively than the other mulches we’ve tried.

So, as you see, there’s a lot for us to consider, even if we’re not going to attempt a big summer garden.  I mentioned that we have a lot of projects going on at my house right now, so we’re leaning towards only doing a few small plantings this summer.  We will probably do some cover cropping in the empty beds, and just come through once a month or so with an application of aerobic compost tea, to keep the soil active.  We’ll feel good about conserving water for a few months, and it will be especially rewarding to get back out there in September to plant the fall crops… after things have settled down with our other projects.  We have a few peppers growing in big buckets.  We’re going to transplant some eggplants and watermelons. Those and our fresh herbs will have to tide us over until the fall.

So the big remaining question is – what should we use for cover crops?  I’ve had good luck in the past with black-eyed peas – I love getting some calories from the “cover crop,” and they’re a nitrogen-fixer to boot.  I’ve used soybeans before, but I wasn’t too impressed since they didn’t really make many edible beans when they were neglected during the summer.  So I’m curious if anyone knows a great cover crop that will perform well in raised beds in Texas, with some neglect through the summer?  Does anyone have experience using lablab as a cover crop in raised beds?  Let me know if you have experience with lablab, or if you have another great idea.

While researching this, I came across a great reference from the University of Tennessee’s Institute of Agriculture Extension.  This document doesn’t go into depth on popular cover crops, but it talks at length about the qualities you should look for in an ideal cover crop.  I thought it was a useful refresher on cover crops, and I thought it might get everyone’s mind racing about creative new ideas for good cover crops.

Click here to read and/or download the original PDF – Cover Crops and Green Manures

Many thanks to Annette Wszelaki, Associate Professor and Commercial Vegetable Extension Specialist, and
Sarah Broughton, Former Graduate Research Assistance

University of Tennessee Institute of Agriculture Extension
Department of Plant Sciences