Adrian Higgins on hypertufa containers and all things gardening

By Jennifer Heffner For The Washington Post
Mar 28, 2019

Washington Post gardening columnist Adrian Higgins took questions on gardening.

Hi there. Given all the rain from last year, our normally-grassy lawn is mostly mud/dirt. Is there anything we can do? Thanks!

Hello, all. Spring is here and things are growing. (To state the obvious). The rain last year -- twice the norm -- was an eye opener and once again reinforces the idea that if you have heavy clay soil, you should systematically amend it so that it will handle more of the wetness. Lawns in particular need good drainage -- this seems counter intuitive because we water them, but standing water is a surefire way to kill turf. One way to do this is to do some rigorous core aeration and then backfill the holes with a sand/compost mix. You could then seed with a turf type tall fescue variety bred for Southern gardens, expect a lot of it to die back in the summer, and do a second core aeration/soil amendment and permanent seeding in September. You could lay sod, but that get's expensive and often fails because the soil is not properly prepped and the turf you buy is not of the highest quality or condition. 

Here is a link to Adrian's most recent column, on hypertufa containers.

I have tulips that just the leaves come up but they do not flower. Do I need to feed them? If so, what time of year do I feed them?

You don't need to feed them, the bulb is primed to flower. However, a little top dressing now of a balanced N-P-K bulb food wouldn't go amiss. 

The last few mornings I have seen the morning temperature down to 29 degrees. Should I have covered up my hydrangeas since they have already started showing sprouts? I remember one year we had a late season 18 degree morning that decimated all the new blossoms, but is 29 degrees nothing to worry about? Thanks.

The short answer is yes. Hydrangeas break bud early and are susceptible to freeze damage. I would have a blanket ready for nights below freezing. 29 degrees might be ok, but I'm not sure I would want to risk it. And please, do not prune your hydrangeas now.   

Hi Adrian. I'd like to add some native plants to our backyard garden. The local garden centers don't always have the best selection. what are your favorite mail order sources for hardy plants, ideally native to the DC area? I'd like to attract more birds and butterflies, and welcome any plant suggestions you have, too.

There are native plant sales in the spring. If you google native plant societies in our region, they should list in their calendar of events the date and locale of these sales. Local nurseries do have a fair number of native plants, but you should think about which ones you want before heading out. Sun/shade? Wet/dry? Perennial/Woody? Etc.  

Is it too early or too late to plant spring bulbs? I want to phlox and dahlias. I am going to plant the dahlias in containers. Is there anything special I should do since I am planting them in containers? I live in Annapolis MD.

Phlox is a hardy perennial that blooms in spring and summer, depending on species. Dahlias are tender bulbs that flower from July to October. You can pot up a dahlia now and take it outside on warm days but bring it in if night temps are below 50. You can then plant dahlias in prepared beds in late May. I would stake it at planting time, so much easier than later on. 

I have unique cut roses from a special occassion I would like to reproduce. Can I grow a small rose bush from a cutting?

Roses can be grown from cuttings, which are taken in late summer and put in trays of sand and covered with plastic to maintain humidity. Use a rooting powder. The success rate can be low, and patience is required. I would grow them in a cold frame or unheated greenhouse over their first winter. 

Hello Adrian, I have two rugosa rose bushes that flower beautifully but struggle with producing full hips. The hips get formed, but shrivel before developing color and reaching full size. Is this an easily identifiable problem and is there anything I can do to fix it? Thank you!

I used to grow a lot of rugosa roses and none set large hips as they do in more northern climes. I think this is a product of a hot, humid climate. If anyone has experience with given cultivars, perhaps they can add to the conversation. 

You recently had an article about repotting plants. You seem to be in favor of putting them in bigger pots. Do you have any tips if I have a root-bound plant but I don't want the plant (or the pots) to get any bigger? Thanks.

Yes, if the roots are obliging, you can simply trim them back a little after you have extracted them and teased them out a bit. This is what bonsai growers do to keep their trees going in the same trays/pots. 

Hi Adrian! I've seen a lot of small growing kits with seeds for flowers and plants for about $1 at places like Target, and I've always wondered how well these actually work and if they will actually produce fruit and/or flowers. What should you look for when you're buying something like this? (Here's a link to a larger version of the $1 version I saw at Target: https://buzzyseeds.com/product/mini-grow-pot-forget-me-not-love-series/)

I don't know about this product, but when growing seeds there are a couple of considerations: Does the variety in the packet grow in your climate and conditions? Second, the seeds should be shown in soil that is open, light and cultivated. Seeds need protection from cold, wind, sun, rain, slugs and squirrels, to name a few things, so this is very much hands-on gardening. The price is the last consideration, given the effort required. 

I have some tomato seedlings and others that are growing ahead of schedule, can I plant outside now or still need to wait?

It's still too cold for tomatoes, and certainly for planting them. You could keep them in a cold frame, if you have one, or you could put them outside on warm days and bring them in at night.  This will minimize their stretching. The one forgiving aspect of tomatoes that are too big at planting time (in about three or four weeks at the earliest) is that you can bury the stems somewhat. 

Please allow me to plug the Northern Alexandria Native Plant Sale, at which I have purchased many many native plants over the years (they have a spring and fall sale)--you should see my gorgeous blood root this week. There are several other sales, shared on this page: https://www.plantnovanatives.org/local-native-plant-sales I have even picked up some natives at Meadow Farms and Merrifield. If you know what you are looking for and are looking for plugs for example, I've heard great things about https://www.northcreeknurseries.com/index.cfm/fuseaction/plugs.plants/index.htm

Thank you for linking to these. 

Is it too late to trim rose bushes ?

Not if they haven't had their annual prune, but hurry. They are about to set tiny flower buds. 

A number of things that have been around for years and done well did not survive all this wetness. At least I'm guessing that's the problem. There were a number places where the drainage simply couldn't handle the amount of water. I can do some things to improve drainage, but what else should I be thinking about as I contemplate replanting?

My first advice is to wait to see if anything grows over the next month. You can also scrape the bark to see if it's green or not. As for replacements, there are many plants that take periodic inundation and there are far fewer plants that take constant wetness, so you need to figure out your exact conditions. The US Botanic Garden's Bartholdi Park is essentially one big rain garden, so I would go there and take a record of their labeled plants. 

I have a few-year old persimmon (I think chocolate--one of the hybrids). I'm an avid gardener, but pruning is a skill that eludes me! I know to remove anything damaged or rubbing, and sprouts that grow straight up, but as to the central leader--do I top it? Diagrams and online tutorials help not helped, can you please explain this in the most simple way possible?

This is a variety of Japanese or Asian persimmon (Kaki). Sometimes the central leader is removed from apples and peaches for ease of harvesting, but I wouldn't do this on a persimmon. It does benefit from a dormant pruning to keep the branches from becoming congested, but I would be conservative with that. And if you are not comfortable with pruning, it's better just to leave it be. Do take off those rubbing branches -- generally remove the weaker one.

Good morning! I'm gradually trying to convert a sloping part of our lawn that is difficult to mow into a mix of groundcover/flowers. It's south facing so gets a lot of sun this time of year, but once a nearby oak tree leafs out it gets varying degrees of shade (half day ---> almost full shade). A couple years ago I started converting the shadiest section first- killed the turf and planted a mix of ferns, PA sedge, and white wood aster, with a bit of creeping phlox as well. The problem is, turf and weeds keep creeping back in, particularly in spots where the plants didn't take off very well. and it's become a lot more high maintenance than I was hoping for. So I'm trying to figure out if there are any other plant options I didn't consider previously, or if I should do anything differently when I move onto the next section? Also, are there any low-growing shrubs that would do well on a slope in the sunnier spots (sun until around noon)?

Converting areas to new plantings requires vigilance during the period of establishment, to keep back creeping turf or weeds and to deal with erosion and dead plants. A thick, lush planting is the best defense against encroachment. Since your plantings are skewing toward native plants, your shrub choice might be native as well. I would consider itea, chokeberry or maybe clethra. 

If you have quite a few, you can set them in a wheelbarrow, making the moving of them (in our case, into the garage at dusk ) simpler.

That's a wheelie good idea!

Do you have hints to improve my lavender to get more blooms? I have different types I have bought as plants and planted from seeds but I do not get lots of blooms. I would love to cut it and bring it in but I don't have lots of blooms.

Sounds like it might not be getting enough sunlight, the problem is lavender doesn't really move well. Do keep high nitrogen fertilizer away from lavender. Removing faded flowers before they seed is another way to promote future flowering.  

I am the person who complained about a rat infestation last summer when a house up the street from me was torn down. all that rain last summer with me directing downspouts to flood rat holes sent them on their way. I filed the rat holes as much as I could with dirt & covered with mulch. now you can't tell they were even there.

And cheaper than the Pied Piper of Hamelin. 

When should they be cut back? Thanks.

Hydrangea macrophylla and serrata shouldn't be pruned at all, at least until they become old and congested. At that point, you should remove entirely  the oldest canes but no more than  a quarter of the shrub in one year. I would do this after flowering in early summer.

We have some rhododendrons in our front yard -- newly-planted last year by the people who sold us our house. Two of them barely made it through the summer/fall, but seem to have survived. What should I be doing now to help coax them back to good health - any particular food? How often do I need to be watering them?

One has to be very selective about the types of rhododendrons one grows here, many do not like hot, humid climates and those that do are native to the mountains. It is important to keep their root zones in the shade, to plant them in acidic, organic soil that retains moisture but drains fairly freely. 

We have a townhouse backyard with nothing but grass to the fenceline and are on a slope getting our neighbors downstream water so we have a soggy yard. Grass seems fine during dryish times, but is there anything low-effort we can do to help the mushiness? It gets half sun there and we are amenable to planting something; it doesn't get any traffic otherwise.

It also sounds rather dull, if I may say so. I would do some serious massed plantings of ferns, sedges and moisture loving perennials. 

Hi Adrian! I just moved into my first apartment and am hoping to start a small windowsill garden, but one that's mostly flowers and herbs. Growing up in California my mom had a nice big flower garden, and I'd love to recreate some of that but in a windowsill garden or indoors. I know this is a tall order, but do you have any tips for flowers that will bloom well together in containers and can handle a moderate amount of light? Thanks so much!

Windowboxes, if that's what you mean, are tough going here because we have screens on our windows and because the plants get terribly stressed in our heat. Shade mitigates this but the price is reduced flowering. I might consider lavender, yes, (English), and other herbs grown more for their foliage and utility. You might sow some California poppy seed for a reminder of home. 

The National Cathedral Flower Mart - May 3, 2019 At the U.S. National Arboretum they have different plants sales https://www.fona.org/gardenfair/ There are more than herbs at Baltimore Herb Festival. One group gives away free trees. http://www.baltimoreherbfestival.com

Thank you for this. On a closing note, do please tackle those winter weeds now as they are about to explode in growth and seeding. It's time too to revive all those summer bulbs and things you have overwintered in trash cans -- bananas, elephant ears, dahlias, cannas etc. Pot them up and get them cranked up for planting in about a month. See you here again soon.

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Adrian Higgins
Adrian Higgins is The Washington Post's gardening columnist. Read his latest columns and stories here and follow him on Twitter.
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