More Fertilizing Tips for Citrus

In February's issue of Tucson Happenings, I discussed fertilizing citrus trees in spring, and I decided that this is an important enough topic to impart a few extra tips on this month's blog.

To begin, I'd like to link University of Arizona's Fertilizing Citrus Chart, which I mentioned in the Tucson Happenings article.  It's a no-nonsense way of figuring out how many pounds of fertilizer you should apply to get the right amount of nitrogen to your tree. Keep in mind that this is the amount of fertilizer you should use in a year, and you'll be feeding 2 more times this year (so you only need 1/3 of the recommended amount each time).

Lisbon Lemon branch with swelling leaf bud.

I also mentioned in my article that the best timing of springtime fertilizer is just before the buds begin to swell, but I didn't have enough room to describe a citrus bud in any detail.

It's easy to notice swelling buds on deciduous trees with barren branches. Citrus trees hold leaves through the winter, however, so their buds are less exposed. You can see the swelling bud on this lemon stem just above the leaf scar.

Citrus trees will begin actively growing when temperatures are staying above about 55° F, so it might be easier for beginners to keep an eye on the weather than it is to watch the buds. Though it's common to hear that you should feed on Valentine's Day, it's better to watch for the right weather and these first signs of new growth. After a warm winter, like the one we've just experienced, you may want to feed a bit earlier in February to give your tree some great fuel for making new foliage.

If you're working with an organic fertilizer, you probably already know that it's not necessary to be so precise in the timing of application. You can feed with organic fertilizers even earlier in the year, because it takes them longer to break down in the soil.

The dripline of the tree is where many of the
absorbing roots are concentrated.

The last thing I'd like to touch on in this post is exactly where and how to spread the fertilizer once you've used the Fertilizing Citrus Chart to figure out how much of your fertilizer to use. You'll have to excuse my extremely rudimentary photo editing skills, but the red lines coming down from the ends of the branches at the right and left are meant to show the dripline of the tree. The dripline is the area under a tree where water would drip off of the ends of the branches (if we ever got any rain...).



If you have gravel, use a hard rake to expose the soil under the tree and a few inches beyond the dripline, avoiding the area just around the trunk. Spread the fertilizer evenly over the exposed soil, and use the rake to scratch it about an inch into the soil.  Make sure you water deeply and thoroughly all the way out to that drip line and beyond, everywhere that you spread the fertilizer (again, avoiding the area just around the trunk). Wait until the soil has dried out a bit before raking gravel back into place or walking under the tree.

Now you can put away the citrus fertilizer until Memorial Day!