If your garden needs nitrogen, a labeled organic fertilizer lets you plan what you add. Compost helps build the soil. Peas or another legume cover crop can add nitrogen for a later crop.
First, check what your plant needs. A yellow leaf alone doesn't prove your plant lacks nitrogen. And kitchen scraps won't tell you how much to add.
Before you add anything
If you're not sure what's wrong, ask a local Extension garden adviser. Bring your notes and a list of what you've added.
- Look at the plant first. Which leaves changed? When did it start? Is growth slower than usual? Check how wet the soil is, how water drains, and how much light the plant gets. Look for pests, too. These clues don't prove a lack of nitrogen. For example, too much water can turn houseplant leaves yellow.
- Garden bed: ask what the soil test includes. Use a lab that gives advice for your crop and area. Follow its steps for taking a sample. Some routine tests don't measure nitrogen. At the University of Minnesota lab, home-garden nitrogen advice comes from the plant's needs and the amount of organic matter in the soil. Organic matter is the remains of plants and other living things. A report with no nitrogen result doesn't mean there's none in your soil.
- Pot: make a separate feeding plan. Check the potting mix bag for any feed already in it. An outdoor pot's needs depend on the mix, watering and plant growth. Houseplants have their own needs. Follow the exact product's directions for your plant and for use in pots. Don't guess a pot amount from a rate meant for a garden bed.
Which materials can help?
Scraps and coffee grounds can go into compost. That doesn't make them a measured dose of nitrogen for a plant that needs it now. Write down what you add, even if you don't know its nutrient content.
Choose a material for the job you need it to do.
| Material | What it can do | What to keep in mind |
|---|---|---|
| Finished compost | Adds organic matter and some nutrients. | How much it adds varies. Repeated use can build up phosphorus, another plant nutrient. A crop may still need more nitrogen. |
| Labeled organic fertilizer | Lists its nutrient content, so you can compare it with the lab's advice. | How fast it feeds the plant depends on what's in it and how it's made. Too much can still cause harm. |
| Legume cover crop, such as peas | Grows to help the soil before the next crop. Can add nitrogen for that crop. | It needs time to grow and a type suited to your area. Plan how to stop its growth before you plant the next crop. It won't feed a struggling plant right now. |
| Used coffee grounds | Can be part of a varied compost mix. | They aren't a reliable quick feed. Adding too much straight to soil can tie up nitrogen for a time as the grounds break down. |
| Crushed eggshells | Contain calcium and break down slowly. | Don't count on them to treat a lack of nitrogen. They break down too slowly to meet a plant's need for nutrients now. |
| Wood ash | Can add minerals and raise soil pH, making it less acidic. | It isn't a nitrogen source. It can change the soil's pH without fixing a lack of nitrogen. |
Choose the amount and timing for your crop
No one product or weekly feeding plan suits every garden. Use the advice for your crop, the product label and your record of past feeds. A general-purpose feed adds other nutrients along with nitrogen. Your soil may not need them.
Copy the lab's advice with the exact units and the area it covers. Keep the product's nutrient content and directions beside it. If the amounts or units don't line up, ask the lab or a local Extension adviser for help before you feed.
Plan ahead if you want to build the soil with compost or a cover crop. If a plant needs nutrients now, ask if your chosen source can supply them in time. Natural materials don't all work at the same speed. A homemade mix has no set feeding calendar. Count what you've already added before you add more.
Keep a simple record
Use one sheet for one garden bed and crop. Gather these notes before you choose a feed or soil amendment, a material added to change the soil. This sheet can't tell you what's wrong with a plant or how much to use.
| Note | What to record |
|---|---|
| Plant and place | Date, crop, bed or area; what changed; checks for water, light and pests |
| Where the advice came from | Lab or local Extension adviser, report date, crop named and what was tested |
| What the advice says | Copy the exact units and area; do not convert them from memory |
| What you've added | Compost, manure or feed; date, amount, units and area treated |
| Before you use it | Exact product or material; label kept; questions you need to ask |
For garden soil. Keep a separate plan for indoor potting mix. Leave unknowns blank and ask for help before you add anything.
Where to go next
For help turning kitchen scraps into compost, read our apartment composting guide. If your houseplant's leaves are yellow, check the University of Maryland's advice on too much water. For a garden bed, ask your lab what it tests and how it gives advice for your crop. The University of Minnesota lab FAQ shows how one lab does this.
Sources
- University of Minnesota Soil Testing Laboratory: Frequently Asked Questions
- UMN Extension: Soil testing for lawns and gardens
- UMN Extension: Do common soil health home remedies work?
- Purdue Extension: Using Wood Ash in the Garden
- Oregon State University Extension: Coffee grounds boost soil health — and help control slugs
- UMN Extension: Cover crop selection for vegetable growers
- UMN Extension: Fertilizing and watering container plants
- University of Maryland Extension: Overwatered Indoor Plants
- University of Maryland Extension: Fertilizer for Indoor Plants
