Applying lawn fertilizer can keep your yard looking healthy by encouraging the rich growth of grass. When you're surveying your lush lawn, you might start to wonder: what else can this magical fertilizer do for my yard? Can I use it on my trees or shrubs?

Stop before you apply the fertilizer! That same product that does so much good for your grass could actually harm your trees. Not all fertilizers will work for all plants, especially if weed killer is an ingredient in the fertilizer.

Instead of applying lawn fertilizer across the entire yard and garden, look for fertilizers specifically designed for trees. Read this guide to find out why you need to be careful with your fertilizers and what to do instead to keep your trees healthy.

Can I Use Lawn Fertilizer For Trees?

Lawn fertilizers are not formulated for use on trees and shouldn't be used that way. In most cases, the fertilizer just won't do any good. In the worst-case scenario, "weed and feed" fertilizers can end up harming the tree. 

Maintaining a yard can be expensive, so we may look for options to cut costs. If you have a tree that's looking a little past it's best; then you might consider fertilizing it. 

Lawn fertilizer is designed to nourish plants, so it's natural to assume it can do the same job for trees. And if you have a bottle of lawn fertilizer waiting to be used, this can seem like the simple solution you need.

Things aren't quite that simple. 

The good news is that regularly fertilizing the lawn is likely to leave the soil well nourished anyway, which will benefit the trees. Regular application of fertilizer can improve nitrogen, phosphorus, and potassium levels in the soil needed for healthy growth. 

But if your trees are looking worse for wear, they may need a direct fertilizer application. Lawn fertilizer is unlikely to be the right choice.

Although many lawn fertilizers won't damage trees, a lot of them just won't do any good. The fertilizers are formulated using specific nutrient balances designed to benefit a specific type of plant. 

The fertilizer that nourishes your lawn won't have the same effect on your trees. It's much better to find a fertilizer designed for tree growth.

And some lawn fertilizers will actively damage the trees. 

What Is Weed And Feed?

Weed and feed is a mixture of fertilizer and weed killer. When you apply it to your lawn, the product should nourish grass while killing weeds. Completing two jobs in one, it's a popular product with many gardeners.

Many trees will have similar features to the weeds you're trying to remove. However, weed killers can struggle to differentiate between weeds and plants with similar characteristics to weeds. The herbicide will kill the weeds but damage the trees simultaneously.

Can Lawn Fertilizer Damage Trees?

A lawn fertilizer won't always damage trees, but the wrong type of fertilizer can cause serious harm. Fertilizers are formulated to do a specific job for a particular plant. Applying it broadly throughout the garden won't have the same effect.

Lawn fertilizer can often damage trees because the fertilizer is designed to kill broadleaf weeds. Weeds can choke a lawn and stop the grass from getting the nutrients it needs. If you have a weed problem, you might consider using a weed and feed.

Unfortunately, broadleaf weeds and deciduous trees have a lot in common. Because of this, the weed killer can attack the trees, mistaking them for weeds.

If you have been using weed and feed and think it's damaging your tree, try applying water across the lawn. A thorough soaking can help disperse and dilute any chemicals remaining in the soil.

Can Lawn Fertilizer Be Used For Other Plants?

Just as lawn fertilizer shouldn't be used for trees, it's best to keep it away from the rest of your plants. This is particularly true if your fertilizer is a weed and feed. The weed killer can damage these non-grasses, mistaking them for weeds. 

Fertilizers contain nitrogen, phosphorus, and potassium in different levels. Lawn fertilizers that don't have a weed-killing element can still potentially be used on other plants, but they're unlikely to have the right balance of ingredients. Using the wrong fertilizer will mean your plants aren't getting the nutrients they need.

What Is The Best Fertilizer For Trees?

The best fertilizers for trees tend to have a higher nitrogen ratio. 16-4-8, 12-4-8, or 12-6-6 are all excellent options. To find the very best fertilizer for your trees, you need to do a soil test. This can tell you how much potassium and phosphorus are present in the soil so that you can buy fertilizer accordingly.

The best time to fertilize trees is in October, before the frost sets in. If you forgot to fertilize in the fall, try fertilizing in March or April, when the frost has first cleared. 

By fertilizing in the fall, the root system has an opportunity to absorb nutrients before the coldest winter months. And there should be some fertilizer waiting in the soil for next year's growth. 

Not all trees will need fertilization, but it often helps ensure they have the best chance of new growth. 

Conclusion

You want to avoid using lawn fertilizer on your trees in most cases. The main reason is that lawn fertilizer is rarely formulated to provide trees with the correct balance of nutrients. Therefore, even regular fertilization won't aid growth.

However, some lawn fertilizers that contain weed killers could be damaging your trees. In this case, you should stop use immediately and soak the soil to dilute the chemicals.

If your trees are looking past their best, consider a nitrogen-rich fertilizer explicitly designed for trees. Your yard will soon look lush and healthy with the correct application.