Basil is one of my favorite herbs to grow and use in cooking. I make a lot of pesto every year and freeze it to use during the winter and spring. I grow basil both in my garden and in pots on my patio and it does very well but eventually it always seems to get a disease of some kind. It starts with what looks like black spots on the underside of the leaves and eventually the leaves turn yellow and the entire plants leaves are affected. Once I see the leaves getting the black spots I stop picking the leaves because I am not sure if it is advisable to use anymore. What is this and can it be prevented?
— William Parsell, Wescosville, PA.
Basil is an easily grown, heat-loving herb widely grown in home gardens and windowsills. It is an annual with a wide variety of tastes, smells, growing habits and sizes. And, as William states, it is essential for making pesto. It is one of those plants that you need more than one of. Recipes often call for a cup or more of leaves for a single, small batch of pesto.
However, there are several common diseases that can attack basil.
Damping off: Seeds or roots of seedlings are attacked and the stems suddenly fall over and die. This is most common under cool and wet conditions. Avoid this by removing any covering as soon as seeds sprout, keeping soil damp but not wet, avoiding cool conditions (a seed starting mat is a good option). This is obviously not William’s problem.
Leaf spot: A bacterial infection that manifests as spots on the leaves accompanied by streaks on the stem. Treat by removing all infected leaves immediately after seeing these to limit spreading. Discard leaves in trash. Avoid overhead watering and water early in the day to allow plants time to dry off before dark.
Root rot: A fungal disease that can stunt plant growth and kill them. Plants often fade before dying. Roots are dark, often slimy. This is usually caused by overwatering, poor drainage and/or poor soil.
Fusarium wilt: This is a soil-borne fungal disease most often found in sweet basil. Symptoms include stunted growth, wilted yellow leaves, brown spots, streaks on stems, and leaf drop. It can spread if infected leaves are allowed to remain in the bed. Plants should be destroyed, not composted and basil should not be replanted in that spot for at least three years. There are varieties that are resistant to fusarium wilt, check the plant information on the tag or seed packet.
Downy mildew: Yellow leaves with fuzzy gray growth on the underside are symptomatic of this disease. It generally appears first on the lower portion of the plant. Control by removing any infected leaves and stems. Space plants to encourage good air circulation and avoid overhead watering and/or water early enough to allow plants to dry off before cool night temperatures.
William’s problem seems most likely to be downy mildew but I welcome others experiencing this problem to write in with their solutions.
Storing Canna and Caladium
Wondering how to keep my canna and caladium tubers over the winter. I’ve tried putting them in peat moss and another time packed in shredded paper. They either rot or totally dry out. Your suggestion?
— Kay
Cannas are beautiful, tall tropical plants grown for their lovely foliage and flashy flowers. Leaves can be various shades of green or red, finely striped or solid. Plants can be miniature (about a foot tall) or huge (almost six feet tall) and anywhere in-between. The flowers come in reds, oranges and yellows, solids, accented or spotted. They grow well in full sun, good garden soil that holds moisture. Smaller varieties can be used in containers but must be kept well watered.
Plants in containers can remain in the pots but must be moved inside to a cool area with above freezing temperatures. Allow the pots to dry out and remove dead foliage. Do not water until you see green growth or a few weeks before the last frost.
Dig and lift canna rhizomes after the frost kills off the greenery. Cut the stalk to about four to six inches and discard foliage, Gently loosen the soil several inches away from the stalk and lift the cluster of rhizomes. Allow the clump to dry and then brush off excess soil.
At this point, there are several options. Some gardeners like to cure the clumps by allowing them to lay in a warm, dry area for about a week before doing anything else. Others store them immediately after cleaning the soil off.
If you have cut, bruised or damaged rhizomes or have had problems with mold/rot in previous attempts, you can dust them with a fungicide or sulfur. Some gardeners treat regardless of the condition of the rhizomes.
The clumps will be divided before planting out next spring so they can be stored whole or separated into smaller sections.
Then, find a cool, dry area where the temperature is between 55 degrees F and freezing. Unheated basements (well away from furnace or water heater), against the wall in an attached garage, or any unheated area that remains above freezing.
One storage method is to wrap the clumps in newspaper and loosely layer them in a crate or bin but do not cover with a lid.
Others prefer to place the rhizomes in peat — dry or slightly moist, or sawdust, well-spaced in a container.
While in storage, check the cannas every month or so. Look for mold or rot and discard problem rhizomes. If you decide to cut out a piece rather than discard the entire rhizome (not the entire clump), dust the cut end with fungicide or rooting hormone (which contains fungicide) and restore.
If your clumps are withering and drying out, you can immerse them for an hour or so to rehydrate but be sure to allow them to dry off before returning them to storage.
Sue Kittek is a freelance garden columnist, writer, and lecturer. Send questions to Garden Keeper at grdnkpr@gmail.com or mail: Garden Keeper, The Morning Call, PO Box 1260, Allentown, PA 18105.
Week in the Garden
Planting: Plant a quick crop like microgreens or frost-resistant crops like collars, short-season cabbage or mustard greens. Plant pansies for fall color and, if you select winter pansies, early spring blooms. Asters and mums are available, buy now for best selection; use either in the garden or as part of a container display. Sow seeds that require a cold period for germination; poppies are one example. Plant perennials, shrubs and trees as the weather cools. Hold bulbs until October.
Seasonal: Allow the final flush of flowers to go to seed. Many provide food for the birds and small mammals during the fall and winter. Take cuttings of those annuals that you want to winter over or other favorite plants that have grown too big to move indoors.
Order asparagus, rhubarb, bulbs, flower and fruit plants, and shrubs for fall planting. Shop nurseries for end-of-season bargains or new fall arrivals. Weed often and cut off flowers of any weeds you don’t get pulled out. Cut back peony greens to about three to four inches tall as the foliage starts to die off. Prune summer-flowering shrubs about two weeks after flowering. Apply corn gluten-based weed control in the garden and establish a schedule for reapplication, usually at four to six-week intervals
Lawn: Seed, overseed, dethatch and aerate lawns Sept. through mid-Oct. Apply broadleaf weed control, Sept. through mid-Oct. Install sod as the weather cools, Sept. and Oct. Treat for chinch bugs and sod webworms. Purchase fertilizer and, if desired, apply now until mid-Oct. Cut as needed, based on growth not schedule, to a height of about 2 to 3 inches tall. Use a sharp blade. Keep newly seeded or sodded lawns watered; supplement rain in weeks where less than an inch. Fill in holes and low spots in lawn. Apply corn gluten-based weed control in the garden; reapply at four to six-week intervals.
Chores: Stop watering amaryllis bulbs. Allow the bulbs to dry out and go dormant. Store in a cool dry area until they resprout in about 8 to 10 weeks. Start planning for fall. Order bulb and plants for early fall shipment. Check seed inventory for late crops and fall planting. Get plants ready to bring in. Repot those that need it and pot up those you want to winter over indoors. Harvest crops regularly, at least every other day. Dump standing water and remove anything that may collect rainwater to help control mosquito populations. Water any recent plantings and containers anytime we experience a week with less than an inch of rain. Repair damaged screens and caulking around windows and doors in preparation for the indoor invasion of wintering over insects and rodents.
Maintain deer, rabbit and groundhog protection for vulnerable plants. Reapply taste or scent deterrents. Clean and fill bird feeders regularly. Clean up spilled seed and empty hulls. Dump, scrub and refill birdbaths at least once a week.
Clear gutters and direct rainwater runoff away from house foundations.
Tools, equipment, and supplies: Check winter/fall equipment, repair or replace as needed. Safety:
Clear lawns of debris before mowing and make sure pets, children and others are well away from the area being mowed.
Store garden chemicals indoors away from pets and children. Discard outdated ones at local chemical collection events. Photograph storm damage before clearing or repairing for insurance claims and file promptly. Anytime you are outside and the temperatures are about 50 degrees F or warmer watch for tick bites. Use an insect repellent containing Deet on the skin. Apply a permethrin product to clothing. Wear light-colored clothing, long sleeves, hats and long pants when working in the garden. Stay hydrated. Drink water or other non-caffeinated, nonalcoholic beverages. Even in cold weather, apply sunscreen, wear hats and limit exposure to sun. Wear closed-toe shoes and gloves; use eye protection; and use ear protection when using any loud power tools.
