IT MAY NOT be growing on trees in this city yet, but there's enough municipal money around for Mayor Barry to produce a promising budget for the fiscal year that will start Oct. 1. The flush times that have buoyed Govs. Harry Hughes in Maryland and Charles Robb in Virginia did not bypass the District. On the contrary, thanks to continually improving financial management, reduced unemployment and strong revenue yields from local taxes, the next decade of home rule in the District of Columbia appears off to a sound start. And as in the two neighboring states, the brighter financial picture provides budget opportunities to improve the lot of the less fortunate as well as to reinforce the physical structure of the city.

On these two fronts, Mayor Barry has struck a reasonable balance, proposing improved financing for schools, mental health services, job training and emergency assistance and shelter, and a capital budget calling for significant rebuilding of streets, bridges and buildings. Though more than a few residents might have preferred some reductions in their taxes, Mayor Barry has wisely seized the opportunity to provide some relief to those most deeply affected by the austerity of the last few budgets.

Mr. Barry and the D.C. Council can take credit, too, for having imposed financial and budget controls that provide more accurate, day-to-day readings on the ebb and flow of municipal cash. Coupled with years of trimming the number of people on the city hall payroll and tightening tax collections, the city's ability to submit prudent budgets to the White House and Congress has improved markedly.

There is one numbers game that Mr. Barry does keep playing every year that seems inconsistent with an otherwise forward-looking financial approach. Again this year, Mayor Barry has failed to include money to help further reduce the city's accumulated deficit, which currently stands at $270 million. While this particular pool of red ink was inherited and is not the result of current amdinistration policies, it needs to be eliminated.

During the past two years, the council has amended the mayor's budget proposals to include some money for deficit retirement -- and it will be up to the legislators to do it again. With that adjustment, the District can present a spending proposal that the White House and Congress not only could and should approve but also could commend as further evidence that self-government and fiscal responsibility can coexist impressively in this capital city.