Interplanting

by Jennifer

"Soon-to-graduate" spinach plants encircle a kiddie tomato plant in a space-saving maneuver.

How many of you grew up with older siblings, and remember anticipating how much more space you'd have when they grew up and moved out? How many of you who are now parents alter your children's sleeping arrangements and room sharing as their changing needs require?

Oh, you do, too? Then you already have a grasp of interplanting. In gardening this is the concept of combining crops for maximum use of space. Here is an effective pairing: plants that mature quickly with those that grow slowly -- radishes with carrots, for instance. Seeds of both can be sown at the same time in the same row. The radishes will be ready for harvest before crowding the carrots. 

Another method of interplanting is staggered sowing of different season crops. This is what I did with my spinach patch, where I later transplanted my tomatoes right alongside. Spinach is a cool-season crop. I planted those seeds in March in the garden plot. By May, when it was time to plant the tomatoes, the spinach was just getting into a groove, showing no signs of bolting (the seed-producing end of the plant cycle, usually brought on by high temperatures). 

I could have removed all the spinach to make way for the tomatoes. Instead, I cleared just enough soil to plant them deeply, keeping most of the spinach plants intact. This pairing rewarded me with a stellar harvest as the spinach kept producing over the next month.  

This picture shows my garden bed at peak spinach production. (Look closely around the tomato cage rings, and you can discern that plant's foliage above the spinach.)

Two weeks later, the spinach started to bolt, and I harvested it all. Here are the growing tomato plants ready to fill their space:

Crop season and rate of crop maturity are two factors of interplanting. Other factors are:

• Plant size. Small, ground-hugging plants like radishes can be planted near taller ones, like beans.

• Light needs. Shade-tolerant plants like spinach and lettuce can be planted very near tall plants like broccoli, or where they are partially shaded by squash leaves. Keep this in mind for fall plantings of cool-season crops. You can plant another crop of lettuce where a summer plant is still producing.

• Depth of roots. This was another factor in the success of my spinach/tomato roommates. Spinach forms shallow roots and tomatoes, deep, so they never competed for water. Incidentally, the basil starts I planted near the spinach didn't fare nearly as well as the tomatoes, and perhaps this is the reason. Like tomatoes, winter squash, pumpkins and asparagus form deep roots. Shallow rooted plants include lettuce, corn and cabbage. (Source: Oregon State Extension)

What are some of your successful plant combinations? How do you maximize your garden space? We love all of your ideas!