Q: Should I fertilize after my plants are up and growing?
A: Regular fertilizing after your plants are growing is a concept many people forget. As a plant grows and produces, it takes up available nutrients. Even if the soil was fertilized at planting time the nutrient reserve could be running low. Fertilize your gardens, especially container plants, monthly when they are producing.
The first nutrient to disappear is nitrogen. The plant may have absorbed all of it or, since it is a free moving nutrient, it could have been washed away.
Nitrogen is the first number on a fertilizer package. So purchase something with a high first number such as ammonium sulfate (21-0-0).
Always follow the manufacturer's directions when applying fertilizer. If you are applying liquid fertilizer, apply it very early in the day or after the sun sets, but still allowing time for the leaves to dry before dark.
Never simply broadcast dry nitrogen fertilizer. Apply it at the base of the plant or the edges of rows and scratch in lightly. This is referred to as a side dressing. Always be careful as fertilizers can burn leaves.
Q. I keep my tomatoes well watered but they still droop in the afternoon. I give them more water but then they die. What am I doing wrong?
A. I get asked this question a lot and there is generally more than one reason for the problem.
First, tomatoes droop in the heat of the afternoon because they are conserving water. This is something we all can understand.
Second: tomatoes can only take up so much water. They draw water up to the leaves like a straw but can only get a limited amount, whether that is because there is either not enough in the soil or uptake is plant. To make up for the lack of water being absorbed, the plant wilts to protect what water it still has.
You could put the plant into a bucket of water and it would still wilt because there is a limit to the amount of water it can absorb.
On a hot day it is normal for the plant to wilt. What you need to watch is if the plant is wilted in the morning. This indicates a need for irrigation.
For the plant to take up more water and avoid wilting, the plant needs more roots. To get more roots, water deeply and keep the soil evenly moist but not drenched.
A tomato plant's roots can go down 2 to 3 feet. The ends of the roots take up most of the water. Water slowly, for a longer time, to get the water to the base of the root structure. This is when a drip system works well.
If you ever wonder how deep you are watering, here is a way to tell. In a vegetable bed, water a spot as if there was a plant there. Wait about a half-hour. Then use a trowel to dig down to see how deep the water penetrated. If the water went down more than a foot, job well done. If not, more is needed.
Another important item for tomatoes is that roots need air. If you water every time the plant wilts, you are over-watering, causing the roots to drown. Eventually they will rot because they are unable to breath, which results in the plant dying.
Q: I have brown spots on the leaves of my 10-year-old pear tree. What's causing that? Could it be a fungus?
A: There are several pests or pathogens that could be attacking your pear. You're right, it could be a fungus. It might also be a virus or bacteria.
The spots caused by fungus vary in size. Viruses cause ring spots and the leaves may also curl, yellow or show stunting. Virus and fungus spots are confusingly similar. You could look more closely at the spots using a magnifying glass, but even then it is hard to tell what you have.
If you can, bring in a sample of your leaves to the University of Arizona Mohave County Cooperative Extension office, 101 E. Beale St., open from 8 a.m. to 5 p.m. Monday through Friday. A Master Gardener could look at them. You can do this at any time, but on July 27, the Master Gardeners are having an "open house" when we will be available to answer questions from the public.
If it is determined that it is a fungus, there are fungicides available locally. Pruning affected areas, cleaning up infected leaves and not allowing irrigation water to hit the tree could be another solution, depending on the problem. We will be able to assist in making that determination.