Adrian Higgins on planting herbs, and all things gardening

By Jennifer Heffner For The Washington Post
Apr 18, 2019

Washington Post gardening columnist Adrian Higgins took questions on gardening.

I've always been told to wait until mother's day up here in Pennsylvania, but with global warming I'm less worried about a late frost. When do you recommend putting annual herbs and vegetable plants in the ground?

Greetings all. Spring is well underway -- my measure is when I see the first of the daffodils fade away. One overcomes the sadness by wallowing in tulips, which I'm doing this week. Two related elements dictate when tender things can go out. One is nightime temperatures. Anything that is the least cold intolerant, such as tomatoes, peppers, basil, should not be planted until temps are reliably in the upper 50s and 60s. One cold night can set them back terribly. The other aspect is soil temperature, which governs among other things seed germination. The soil takes longer to warm, which is why I wouldn't plant summer edibles until early May in Washington and probably mid May in Pa. Before they go in, they should be conditioned to the outdoors, and this includes shelter not only from cold, rain and hail  but also from the sun and the wind. 

My kid really wants to plant some strawberries and I have no idea how to go about it! We have an enclosed bed of dirt in a sunny spot. Should I get seeds, can I buy strawberry plants at a nursery, is this the right time to plant...?

It's sort of too late for seed starting, and seed starting is something you graduate to as a gardener. You can buy plants now and they should be set in a sunny, well prepared and weed free bed, and given a mulch (of straw, hence their name) to keep moisture even. When the fruit develops you will be in a race with the animals to harvest them. Netting might be in order, though that comes with its own challenges. Alpine strawberries are smaller, tastier (to my palate), function in partial shade and yield for much longer.

Do I need to worry about lavender spreading into areas that I don't want it to like mint and its relatives??

No. You need to worry about lavender receding -- a lot of it has perished around here after six feet of rain in 2018. My herb story today will tell you what to do: https://www.washingtonpost.com/lifestyle/home/what-herb-lovers-should-know-about-planting-lavender-thyme-basil-and-more/2019/04/15/ff421e6c-5b10-11e9-9625-01d48d50ef75_story.html?utm_term=.ecfd3f42356a

 

Hi Adrian! I'm moving cross-country and am thinking of driving from the West Coast to the East Coast. I have a lot of plants that I would be very sad to leave behind because I've put a lot of effort into nurturing them over the years. Do you have any suggestions for packing them up for the drive? I don't think shipping would be feasible.

I don't know what sort of vehicle you have, what plants you have or their size, so this is a general response: If they are in pots, you could place them in plastic crates to keep them from tipping and jostling. However, if you don't have the room for them, I would take each plant out of its current environment, keep much of the soil around the roots, wrap wet paper towels around the roots, add plastic bags, and lay them carefully in cardboard boxes. I would soak all the plants well a day before digging/unpotting. They should be ok for a few days like this. Do not leave them in a hot, parked vehicle for very long, however. When you arrive, you will have to quickly repot them and get them in their preferred light conditions. Do not transport plants unprotected in the open bed of a pickup truck -- the desiccation will do them in.

I've got the basics in my herb garden, rosemary, oregano, tarragon, sage, parley, and chives and basil. Are there others, either annual or perennial that you think would make an especially interesting or useful addition to the garden?

In my story today, I add lavender, which has a limited culinary use but is such a pretty and evocative herb. I am a big fan of cilantro and chervil  -- best grown in spring and fall in our region, and easy from seed.  

I live in an old apartment and have had a lot of really weird insects crawl out of my AC vent. I’ve found that a couple of different insects have made their home in my house plants, including house centipedes and sowbugs. The bottom trays of some of my plants have tiny baby insects crawling all over (while fully matured bugs live throughout the soil) and I’m not sure what to do about once I move out. I’ve used neem oil for pests like aphids and red spider mites but not sure what the best practice is for this situation since the soil itself seems infected? Is the best thing to do just repotting the whole plants?

I used to think sowbugs were harmless until last year, when they multiplied like crazy (I think because of the rain) and then started rasping away at my carrots. If you have tenacious pests in your houseplant soil, one way to deal with them is to fill up your bath and submerge the pots overnight. Don't forget to drain them the next day. 

Hi Adrian, The previous owner of our home planted many beautiful flowers in the garden, but also planted morning glory. The morning glory grows very quickly and chokes the other plants without constant maintenance and pruning. What are your tips for getting rid of the plant entirely?

This is very deep rooted and almost impossible to dig out, and I don't use herbicides, so I just pull the vines as they grow. Eventually this will weaken them and they go away. Make sure that none of the seed pods from last year are still about. 

I live in upstate NY and over-winter my herbs in the garage (thyme, oregano, mint, sage) in their pots. Rosemary gets over-wintered indoors. I mainly do this so I have them to use over the winter, but they do seem to come back nicely. Only the thyme looks a bit ragged. Should I wait until it looks better or just start with a new thyme plant?

Thyme definitely benefits from a grooming at this time of year. Trim it back but keep it, and then give it some companions. As I say in my article today, herbs are best viewed as short lived perennials, and the act of buying new ones in April is, to me, one of the great joys of spring. 

We live in the DC area & want to clean out the brush in our yard and plant evergreen trees. Is there a best time of year to do this? Ok to clear and plant at the same time?

I think unwanted and uninvited plants can be grubbed out at any time. My favorite tool for this is a mattock. Beware of burgeoning poison ivy. You could plant now, though make sure the roots are correctly manipulated, set at the right level, and given a light mulch. The best time to plant most woody plants is in late summer, early to mid fall. 

Hi Adrian, we're trying to start some hot peppers from seed this year and haven't had much success. Almost all started out ok then died. Out of about 80 seeds started, we have about 10 that are still alive. I know we're too late to restart this year... Any tips on how we could be successful next year?

If they germinated and then suddenly collapsed, they died from a fungal disease associated with cool soil and insufficient air circulation. My advice for peppers is to give them bottom heat by way of a heat mat -- this speeds germination and minimizes fungal issues. At this point, I would buy pepper transplants for setting out in early May. 

Just want to direct some attention to the other major newspaper today on an opinion piece by Oliver Sacks on the Healing Power of Gardens. I couldn't agree with him more.

This is in the NYTimes, I don't have a link handy, but definitely worth a read. Gardeners, of course, know all about the healing powers of our life practice (hobby is such an inadequate word).

Adrian, I received a potted Gardenia as a gift and am wondering if I can plant it outside.

Dodgy. There are some hardy cultivars of gardenia -- but even these perished in DC over this past winter. I think the rapid freeze in January did them in. Yours is greenhouse grown, and will need to be hardened off before planting, and then only in a very sheltered location. Might be worth a go.  

All over my neighborhood right now, I'm seeing a lovely plant, kind of a groundcover that spills over hardscape ledges in such a lovely way, with green foliage and pink or purple flowers. Any clue what this is? Lots of people have it, but I'm a bit too shy to go knock on doors and ask plant questions!

It's probably creeping phlox. 

Last Fall, I noticed deer were eating my ivy leaves, but leaving the leaf stalk. Now, in the Spring most of my ivy, which was ground cover, easily 10K sq. feet, is dead. Vines are brittle and dead. Now the only places ivy leaves are seen is under bushes or hard places to reach due to a rocky landscape. Is there a connection to the deer?

I think not. Ivy is prone to a bacterial leafspot disease for which the remedy is to cut out all the dead branches. English ivy, by the way, is considered a passe plant because when it matures and seeds, it becomes a major invasive weed in natural areas. 

In your column this week, a reader asked where to find native plants in our area. My favorite source is a small nursery on Calvert Street in Alexandria, just south of and across from the Potomac Yards off of Route 1. It's called Nature By Design (https://www.nature-by-design.com/), and sits at the very end of Calvert's industrial strip, where you'd least expect to find a nursery. They specialize in native plants (and sell only a few, well-behaved non-natives). I just visited them this week to pick up a trillium cuneatum and native azalea (My Mary). I've bought lots of plants there over the last few years, and I've never been disappointed. The plants are well tended, and I never have to deal with the impenetrable root masses characteristic of pot-bound plants from the bigger commercial nurseries. It's a great asset to have right here in the DC area. Ravena Creedon

Good lead, thank you. 

Is there anything I can do to save an old declining dogwood tree? This Spring it has more dead branches than in past seasons. Thanks!

When any tree is declining, pruning out the dead branches becomes essential. Often they are diseased and the pathogen makes its way down the vascular system. Once it reaches the trunk, it's game over.  

Which herbs do deer eat and which do they avoid? Is there a way to discourage them from eating plants by including plants they dislike next to those that they like? I don't want to spray the herbs with deer repellent, which really stinks.

The essential oils in herbs are not attractive to deer, though no plant is safe if they are hungry enough. It may well help to intersperse herbs amid deer prone plants, though I would start small in your experimentation. 

Hi Adrian - Crabgrass is the bane of my existence. It is quite persistent across our rather large yard. We try to dig it up, but it is very difficult to stay on top of all of it. Are there any safe, organic treatments to suppress crabgrass? Thanks.

The one I know of is corn gluten, which has the added benefit of feeding the lawn. The downside is that it's more expensive than chemical treatments and may need repeated applications. 

Hello Adrian: I'm an amateur gardener who is filling in for my elderly mother this spring. 3-4 weeks ago, I thought I had pruned back the knockout roses to the correct level (about 3 to 3 and 1/2 ft.). Recently, she got a look at them and said that I have to prune them back more (along with other roses that are smaller). How much more? And is that safe with our warmer temperatures? I'm particularly concerned about the more delicate roses (e.g., French Lace) which have never been robust in our clay/compost mixture of soil. Most of our roses are hybrid tea roses. Thanks for any advice and we enjoy reading your columns.

Rose bushes are best pruned in late winter, in dormancy. The general idea is to leave five or so main canes in a way that removes dead and crossing branches and opens up the center. They should be cut back to 24 inches or a bit less to just above an outgrowing bud (or now shoot).  I suppose you could still prune now, even though we are a month from flowering. Put thumb tacks or wood glue on the exposed cuts to prevent borer damage. 

I have to move some daffodil bulbs because of construction, how and when should I do that. Thank you.

Daffodils ideally need at least six weeks of leaf growth before they should be lifted. If you have to move them now, be very careful to not damage the roots or the foliage, and place them in a prepared bed at the same depth, and in a sunny location. You can then move them to a permanent location (if needed) in June as the foliage fades. 

How late is too late to prune fruit trees? We have plum and apricot trees that have very long top limbs that should probably be pruned back. However, the trees have already flowered and leafed out, so I'm assuming now would be a bad time to prune? When is the best time to prune fruit trees?

Most fruit trees are in the rose family, and should be pruned in winter dormancy. You might thin some of the young fruit clusters for bigger fruits, but otherwise wait for branch pruning. These are relatively high  maintenance plants and most growers will have a spraying regime against certain pests and diseases. Neglected plums and apricots will not be happy campers in our part of the world. 

2 seasons back my indoor plants - which lived during out winter on a rack above the floor & just inside my sliding [apt] balcony doors with Southern exposure - got 'sick' with what a garden shop suggested was plant mold disease that [they said] arises indoors. Does such a plant problem stay forever? How might I again attempt an indoor plant kingdom? - Deborah Alexander, Chatham. NJ

Indoor plants can indeed get afflicted with fungal diseases, often when it is too dark, too moist and too cool. The remedy is more light and a fan playing on them. I see we are out of time, but thank you for all your questions and hope to see you all here again very 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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