Q & A: Flowers

dahliasGot a gardening question? Ask Susan! What follows are reader questions. Each time a new one comes in, I’ll add it to the top. To ask a question, drop me a note at Susan@susansinthegarden.com.

Q: I planted a trumpet vine 3 years ago. I unfortunately fertilized it in the first year, thinking that it would produce more blooms. Instead I got beautiful, thick green leaves. I have not fertilized it since the first year, but it still has not produced flowers. It is beautiful and has healthy foliage. Will it ever bloom or should I dig it up? PA

A: That’s frustrating about your trumpet vine not blooming yet. It’s true that if you put a nitrogen fertilizer on a plant that needs to bloom, it will encourage more leaves than blooms. As long as it’s in a sunny spot and is getting regular water, it sounds like you’re doing the right things. I did find information online that says a trumpet vine can take up to 5 years to bloom, so I would skip the fertilizer and see what happens in the next year or two.

Q: I don’t understand what half-strength dilution means referring to the fish fertilizer. Could you tell me how much to use per gallon of water? OLR, Spokane

A: When I fertilize young seedlings with fish fertilizer, I like to use it half-strength to avoid burning or overfeeding them. This means using half as much fish fertilizer from what is recommended on the label. So, for example, they recommend 2 tbsp. of fish fertilizer to a gallon of water for vegetables, bedding plants, bulbs and annuals. That means I will use 1 tbsp. of fertilizer to a gallon of water.

Q: Do you grow roses? I have pruned them a little in fall so the snow load won’t break the long stems. I’ve had people here tell me not to prune them before winter because it is so cold here. The other thing I am being told is to put straw around them about 12 inches high for the winter. I have been doing this but since my roses are hardy for zone 5 I was wondering if I really need to do this. CG, Spokane

A: Yes, I do grow roses and the majority of them are own-root (non-grafted) roses, which means they are quite winter-hardy and do not require mulching for the winter. If you have grafted roses, you will definitely want to mulch them since the graft is the one weak point on a rose. Re: pruning them, if you have any particularly long canes (such as 4′ or longer), I would recommend trimming them back so they won’t whip around in the winter winds. In general, regular pruning is discouraged here after about Labor Day because pruning tends to encourage tender new growth that is susceptible to winter kill.

Q: One of my hanging begonias is dropping the bloom before it even begins to open. I thought it may be too much water….but the leaves are not turning yellow. Any ideas? BN, Coolin, ID

A: There are 2 common causes of blossoms dropping off begonia plants: 1) overwatering them or 2) locating them where they get too much sun. Seems like #1 is the more common cause, though. Not sure if you’re growing tuberous begonias, but if you are, here’s a factsheet on them that might be helpful: http://www.spokane-county.wsu.edu/spokane/eastside/Fact%20Sheets/C007%20Tuberous%20Begonia%2007.pdf. I’d poke my finger into the potting soil down to the 1st or 2nd knuckle and see how damp it seems. Good luck!

Q: Your column in the June 26 Sunday Spokesman about heucheras has prompted me to send you a question about them. In the spring of 2015 I planted several ‘Carnival Peach Parfait’ heucheras and they’ve done very well. Last year they had a few short flower spikes but the blooms didn’t open. This year the plants are bigger and have lots of flower spikes but after several weeks the flowers haven’t opened. Are they not supposed to open? MJB, Moscow, Idaho

A: Heuchera blossoms tend to be quite tiny, so I think your ‘Carnival Peach Parfait’ heucheras are doing exactly what they should be doing. There are some cultivars that have a bit larger flowers but, for the most part, heuchera flowers are rather diminutive, taking a back seat to their amazing leaves!

Q: What does deadheading mean? I can snap off older marigold heads easily; I can pull flopped-over petunia flowers easily. I cannot remove daisies, for example, with my fingers so what does deadheading really mean? Do I cut certain things off with snippers? SS, Spokane

A: Deadheading is the removal of spent flowers to either make the plant continue blooming (i.e., flowering plants) or to prevent a plant from self-sowing (i.e., a plant that could be invasive). In the first case, if you don’t remove the spent flowers, the plant tends to stop blooming because it’s whole purpose in life is to have some flowers be pollinated, set seed and die. By removing the spent flowers, you can keep the blooming process going in most cases so the plant won’t focus all of its energy on maturing the seeds in the flower heads but rather, on blooming again. Yes, there are certain flowers you can’t snap off with your fingers so you’ll need to use scissors or pruners, or something along those lines. I would remove as many spent flowers as is feasible for you. However, I like to leave the late summer flower heads on plants like bee balm, black-eyed Susans, globe thistle, and coneflowers so birds will have seeds to eat during the winter months. It’s great fun watching birds landing on the seedheads and eating the seeds!