Wednesday, August 12, 2009

Row Covers for Worm Free Broccoli!

In the past, I've told of our success in using row covers in our garden here . I've had several questions about using row covers, and thought I should revisit the topic!

Row covers are thin white "fabric" that is used in the garden to cover plants. These row covers allow water, air and sunlight to pass through but help protect the plants. The row cover will help to keep the plants warm but my favorite use is to protect from insects. Of course, insects that burrow up from the ground will not be deterred but flying insects will no longer be able to bother the plants.

My best success has been with broccoli. Though our garden is not entirely organic, I do avoid the use of chemicals. I especially hate to spray any plant that I'm intending to eat. If you've ever grown broccoli, or any other plant in the brassica family you know how much the cabbage worms love them! These tiny worms blend right into the broccoli until you are cutting it up for a salad when they seem to reappear! I'm not the squeamish type when it comes to worms. (Just don't let me see a snake!) I try to remember that if a vegetable is edible to a worm, it is edible to me. In contrast with the grocery store broccoli that can't sustain life for a worm, and maybe not me either! But picking worms out of your supper isn't real fun! Which is why I LOVE row covers!!!

The first year I tried growing broccoli under row covers, I did so just to protect it a little from late spring frosts. When it came time to harvest, I was shocked to find NO tiny green worms! I quickly assumed that the butterflies could not reach the plants to lay their eggs on the leaves! After picking the broccoli heads, I removed the row cover. The plants later produced lots of side shoots which I also picked. But this time, we had many worms! I was now sold on the use of row cover for broccoli! We have used it every year since with continued success! No spray and no worms works for me!

Others who are plagued with the cucumber beetle in their vine crops have also found success with row covers. The cucumber beetle burrows into the stem of cucumbers, squash and other vines. The damage usually isn't immediately evident but the vine is stressed and usually about the time it begins to bare fruit, the plant wilts and dies. Row cover can protect these crops from the beetle when they are young. As the plant matures, the row cover needs to be removed in order to allow bees to pollinate the blossoms.

When should you use row covers? Plants should be covered with row cover immediately when set out in the garden. Don't even allow a few days to go by because those insects may beat you to it! The best way to cover the plants is to make a "hoop house". Use thin flexible pipe and bend into an arch. Either just push the pipe into the ground or drive some rebar into the ground and fit end of the pipe over it. Use these hoops to support your row cover. We have also just laid the row cover directly over the plants without the support of hoops, giving slack in the cloth to allow for plant growth. Go here for better directions!

Securely hold the row cover to the ground with clips, rocks, or boards. You don't want it to blow away or have any holes for insects to find. When you are ready to harvest, just flip back the row cover, pick and replace.

One idea I saw in the Berlin Seed catalog was to sew up some fabric "socks". Fill with sand or stones. Use the socks to hold down your row cover.

We have found row cover six feet wide is a useful size. This width allows adequate room to cover full grown plants.

Where can I find row cover? I've seen them sold online, in seed catalogs and at garden centers. This spring I called several local garden centers. Most carried some sort of row cover, though they went by many different names and brands and came in many different sizes. The folks at Veggicare generously gave us a piece of Mikroclima to test in our garden this spring. Mikroclima is a woven row cover and much more durable then most row covers. With careful use, any row covers can be used for several years. Our original piece of row cover we kept using even after it had holes but we had to careful fold and place rocks over the holes. Commercial crop farmers use row covers as a disposable product, replacing each year. Mikroclima, in contrast with other brands, is made to last much longer. We used Mikroclima for several months this spring and it shows no sign of use. I like that dirt doesn't seem to stick to it like other row covers. We bought a standard piece of row cover from our local garden center just to test it side by side with the Mikroclima. In my opinion, both kinds work, but the Mikroclima is much more durable. The extra cost of the Mikroclima may be worthwhile to have a product that gives you years of service.

What is advantage or disadvantage of using a row cover instead of a transparent plastic hoop house? Hoop houses covered in transparent plastic are often used as a cold frame to extend the garden season. Basically a plastic covered hoop house is a mini greenhouse. It heats up quickly in bright sunshine and can enable you to grow crops later, or earlier, then your normal growing season. The drawbacks of using plastic is that no rain or air can enter. On a bright sunny day, even in the winter, a plastic cold frame can overheat and fry your plants. Water and temperature need to be consistently monitored. Row covers, in contrast, allow water and air to pass through. You still need to check the moisture level occasionally but you should not need to remove the row cover to cool down. Of course, it also doesn't not keep it as warm as plastic may. What you wish to use may depend on your goals and how much time you have. I have more on my mind then regularly checking a hoop house and I know that any young plants would be doomed if their life depended on me to give them all their air and water. Row covers have worked well for this busy mom!

Some companies offer several different weights of row covers. There is thicker row covers that allow less sunlight to pass through but protect from colder temperatures. Thinner row covers don't do as well in cold weather but give more sunlight. The thinnest row covers do nothing to protect from cold and frost but merely give insect protection.

Hope I've answered all your questions and that some of you give row covers a try in your garden!


  1. You are a life-saver! I am going to try this. Thank you for the post. I love your blog!

  2. I have a small planter box that I planted brocolli in a couple weeks ago. Almost all the seeds took and I have lots of growth close together. Should I remove some of the plants or can that grow close together?

    1. Noelle-
      Broccoli grows quite large. It is good for them to have at least a foot of space to reach maturity. So you will have better success if you remove the extra plants.


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