Edited by Therese Ciesinski, In The Dirt newsletter editor
I planted two climbing Red Blaze roses on a trellis this year. Do I cut them back this winter? When and by how much? Thanks.
You don’t say how long the canes are, but if you just put them in the ground this year, the plants probably aren’t mature yet, and are putting their energy into developing good root systems versus abundant top growth. If you are fertilizing, stop, because you don’t want to encourage new growth that will be killed by frost. Keep watering, however, as long as the ground isn’t frozen.
Once the weather gets cold, tie the canes loosely to the trellis so the wind doesn’t whip them around, but don’t cut any off. Roses are usually pruned in late winter while they are dormant. While canes that are dead, diseased, or damaged should be pruned, your plants aren’t likely big enough yet to need serious pruning.
Don’t miss expert rosarian Stan V. Griep’s article on winter rose care in GardenSMART’s October newsletter. You can sign up for the newsletter here.
Aphids on Tomatoes
I tried to grow tomatoes on my apartment patio. The aphids ate them last summer and this summer along with the sunflowers I planted. My hanging pots of impatiens, petunias, and geraniums are fine. I used an aphid spray but it did no good. How can I get rid of the aphids? I threw the entire pot and plant away.
Spring Hill, Kansas
Aphids are tiny, soft-bodied insects that suck the juices from plants, causing wilting and yellowing of leaves. Aphids can be white, brown, green, black or rust-colored. Aphids multiply exponentially, and can transmit viruses from one plant to another. They secrete honeydew, which makes the leaves sticky.
Aphid infestations are rarely bad enough to merit throwing away a plant, but they can be attracted to a plant that is already stressed and will add to the damage. Try again next year: start with healthy plants from a reputable nursery. Make sure the plant isn’t root bound and the potting mix is fresh. Site the plant in full sun and a place with good air circulation. Don’t over-fertilize; aphids are attracted to tender new growth. And be consistent with watering, the mix should never completely dry out.
Check the entire plant for aphids every day or so, and if you see any, gently wipe them off with a wet paper towel. That should keep their numbers down. If, despite monitoring, the aphid population explodes, spray the plant with insecticidal soap or neem oil according to the directions on the bottle.
Container Potting Mix
What type of soil mix is best for container gardens?
The best type of soil mix for containers depends on what you want to grow. What we call soil mixes are often soilless, with the primary component sphagnum peat moss or coir (coconut fiber). Soilless mixes are light enough for air, water, and roots to easily penetrate, but have enough mass to support those roots, hold moisture and nutrients, and not dry out too quickly.
Common ingredients in commercial soil mixes are peat moss or coir, perlite or vermiculite, lime to correct the pH, and sometimes fertilizer. There are different mixes for different types of plants. Succulent mix, for instance, contains sand, for a drier, faster-draining mix than one for annuals or perennials. Container mixes for vegetables usually have added fertilizer.
Garden soil or topsoil is usually not recommended for containers unless it has been sterilized to kill pathogens and weed seeds, and lightened with more porous ingredients.
You can buy pre-bagged mix at the store, or you can make your own container mix, experimenting until you find a combination of ingredients that works for the kinds of plants you grow. The Penn State Cooperative Extension has detailed recipes for soil- and soilless mixes here.
I would like to plant host plants for our native butterflies. My yard is sunny with some shade. What time of year should I plant milkweed? Thanks for a great program!
Monarch butterflies are declining in number due to habitat destruction and pesticide use both in the U.S. and in their overwintering sites thousands of miles away in Mexico. Eliminating habitat also eliminates milkweed, the only plant monarch caterpillars eat, so it’s important to replace this vital food source in our gardens.
There’s more than one species of milkweed. All are natives, and most grow wild in fields and swamps. For garden purposes the most popular is butterfly weed (Asclepias tuberosa), a perennial that grows about three feet tall. It has clusters of bright orange flowers that are as appealing to people as they are to monarch caterpillars. Butterfly weed needs full sun to bloom; at least six to eight hours a day.
Whether you start plants from seed or get them from a nursery, you can plant butterfly weed in spring after the last frost in your area, and into the summer. Many species of butterflies will sip the nectar from the flowers, but you’ll know you have monarch caterpillars when you see black, yellow and white caterpillars devouring the leaves.
When most of the leaves are gone, cut the plant back to about three inches from the ground and it will produce new shoots. Butterfly weed is slow to emerge in spring, so leave the stems of last year’s plants in the ground as a marker so you don’t accidently pull the plant up and throw it away, thinking it’s dead.
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