Garlic at a Farmers Market.
Photo by Lynn Ketchum, OSU
By Kym Pokorny | For The Oregonian/OregonLive
The gardening season has started and if you’ve got questions, turn to Ask an Expert, an online question-and-answer tool from Oregon State University’s Extension Service. OSU Extension faculty and Master Gardeners reply to queries within two business days, usually less. To ask a question, simply go to the OSU Extension website and type it in and include the county where you live. Here are some questions asked by other gardeners. What’s yours?
Q: Why is there a reddish/purplish color on tips of garlic leaves? I know what rust is and this is different. It could possibly be a nutrient deficiency, and if so, what nutrient? Garlic was planted in October 2020 in raised beds with plenty of native soil that is heavy clay and amended with straw all winter. Lots of worms. Most greens are at least a foot or more tall. I’ve had problems with allium rust before, but not this. Also, it’s been three years since I planted garlic or other alliums in this space. – Polk County
A: This is most likely a nutrient deficiency, a lack of phosphorus. Start with a composted manure and water it in. There are many products in the stores. Then drench the soil with fish or seaweed (kelp) emulsion, following the directions. Use the liquid fertilizer every four days for 12 days (three times). You should see a difference in the garlic, greener and with the composted manure and the liquid fertilizer they should be healthier. The purple tips may not go away though.
Garlic can use a lot of nitrogen, which is in both of the nutrients I mentioned as well as the other nutrients that the plants need. If it is the hardneck variety of garlic, it will start putting out a flower called a scape. Wait until it starts to curve like a snake and then cut it at the stem base. Do not cut any of the leaves. Do not let the flower open while growing on the plant. This will send more energy to the bulb instead of the flower. Scapes are great in salads or eggs, used as a mild garlic in cooking.
If you think the plants still need the liquid fertilizer, continue once a week making sure the garlic is well watered but not sitting in water. You can continue using the liquid fertilizer on a weekly basis through May. Stop in June. Let the plants grow to their final stage, harvest when you see the bottom leaves dying. Usually end of June.
When you prepare the soil for garlic, always add composted manure. You can grow a cover crop as well in the bed sometimes called a green manure, which will add nitrogen to the soil. There are many crops that will help with this, to name a few, oats, vetch, rye, clover, Austrian pea, etc. Before the green manure starts to flower, cut it and let the cuttings stay on the bed. They will degrade and leave more biomass in the bed for the plants to use as it decomposes. You cut the plants down before they flower to keep the nitrogen they store in their roots and therefore in the soil for the garlic or whatever you wish to plant there.
Examples of phosphorus deficiency:
Q: Presently I am growing potatoes with the garlic. Not sure, but thinking that your directions for the garlic would benefit the potatoes as well, at least at this stage. I also have good luck with buckwheat so wondering if adding seed to the area now would be OK.
A: Garlic does not like to have anything planted with it. That may be why you have purple tipped leaves. Potatoes and garlic are both very nutrient hungry plants. Next year, if you can, plan on planting your garlic alone.
Do not plant anything else with it either. Every plant that you put in the same bed will take some of the nutrients from the garlic. You will have bigger bulbs and if you dry them sufficiently longer-lasting flavor in the garlic if you plant alone.
Potatoes do benefit from the nutrients I mentioned. Again, they should be planted alone. The buckwheat needs to go in another bed so it will not take the needed nutrients away from the garlic.
Depending on how many garlic cloves you plant, you might put them in a deep pot. If you are planting 10 to 15 cloves a 20-inch-deep pot would be able to produce some nice sized bulbs. Fill it with compost, potting soil and add a cup full of chicken manure, and mix. Plant the same as in a regular bed.
– Sheryl Casteen, OSU Extension Master Gardener
