Dear Jessica: I have a terrace and always have success with my plants, but for some reason grass is growing along with my flowers. I went to my local nursery and was advised to put down Spanish moss to prevent more grass growing. It has helped a little but not enough. Why is this happening? And can you give me some advice on how to get rid of it and prevent it from happening in the future?
_ Maria Conte
Dear Maria: You don't say whether you bought larger plants already settled into their containers or if you transplanted seedlings into pots using potting mix or garden soil.
I always advise folks never to use garden soil to start seeds or fill containers because, in addition to being heavy and dense _ which isn't optimal for containers, seeds or seedlings _ it can harbor weeds and seeds, diseases and pests.
If you didn't use garden soil, it's entirely possible the potting mix used (whether by you or the nursery) was contaminated with grass or weed seeds. For this reason, only purchase high-quality, sterile potting mixes, and start with fresh mix every year.
If you reused a container without thoroughly cleaning it, residual soil debris may have contaminated your plants. When reusing pots, always wash them in hot, soapy water, and disinfect them using a 90-10 water-to-bleach solution, then rinse well before planting.
There's also a chance that airborne seeds are landing in your pots. It's less likely than the other scenarios, but possible especially if your terrace is on the ground level and right above a lawn.
Applying a quality mulch made of hardwood or pine bark (Spanish moss works, too) to the soil surface will go a long way toward eliminating weeds because seeds that settle on the surface will have difficulty germinating. Mulch also prevents light from reaching the soil, creating another deterrent; Spanish moss serves the same purpose. However, if seeds already in the soil have sprouted and taken root, mulch won't likely dissuade them. For now, dig up the grass by its roots, then top dress with quality mulch. Following these guidelines should prevent a reoccurrence next year.
Dear Jessica: My friend gave me, a plant she calls "Louis flower," but thinks she made up that name. Can you please tell me what this plant is, and in what conditions it will thrive?
_ Mary Ellen Gambardella
Dear Mary Ellen: Your plant is rose campion (Lychnis coronaria). Growing up to 3 feet tall, the plant, with its velvety silver foliage, branched stems and showy magenta flowers, thrives in full sun and blooms in late spring and early summer. In addition, the clump-forming profuse bloomer is deer- and drought-tolerant, and self-sows readily. If you don't want it to spread, be sure to deadhead flowers as they fade.
Rose campion doesn't typically take kindly to being transplanted, so if you'd like to propagate it, collect seeds when they form, store them in a paper envelope in the refrigerator (away from fruit) and sow directly in the garden early the following spring.
